Common Bees of Western North America (Princeton Field Guides, 124) 2022045093, 2022045094, 9780691175508, 0691175500

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Common Bees of Western North America

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C W

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Common Bees of Western North America Olivia Messinger Carril and Joseph S. Wilson

princeton university press princeton and oxford

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Copyright © 2023 by Olivia Messinger Carril and Joseph S. Wilson Princeton University Press is committed to the protection of copyright and the intellectual property our authors entrust to us. Copyright promotes the progress and integrity of knowledge. Thank you for supporting free speech and the global exchange of ideas by purchasing an authorized edition of this book. If you wish to reproduce or distribute any part of it in any form, please obtain permission. Requests for permission to reproduce material from this work should be sent to [email protected] Published by Princeton University Press 41 William Street, Princeton, New Jersey 08540 99 Banbury Road, Oxford OX2 6JX press.princeton.edu All Rights Reserved Library of Congress Cataloging-in-Publication Data Names: Messinger Carril, Olivia, 1976- author. | Wilson, Joseph S., 1980- author. Title: Common bees of western North America / Olivia Messinger Carril and Joseph S. Wilson. Description: First edition. | Princeton, New Jersey : Princeton University Press, [2023] | Includes bibliographical references and index. | Summary: “Common Bees of Western North America, a companion guide to our recently published Common Bees of Eastern North America, is the first species-level photographic field guide to the most commonly seen bees in the western United States and Canada. Identifying bees by species is challenging even for taxonomists. This book walks readers through the process of bee identification using breathtaking high-resolution color photos that highlight the unique characteristics of each species, making identification easier. Each species will be presented through multiple images highlighting key identifying marks, as well as silhouette images depicting the actual size of the species. Key identification features, size, phenology, floral preference, nesting, and related species will be described with range maps for every species. The book will close with a taxonomic key to bee genera of the western United States and Canada”-- Provided by publisher. Identifiers: LCCN 2022045093 (print) | LCCN 2022045094 (ebook) | ISBN 9780691175508 (pbk ; acid-free paper) | ISBN 9780691249438 (e-book) Subjects: LCSH: Bees--West (U.S.)--Identification. | Bees--Canada, Western--Identification. | BISAC: NATURE / Animals / Insects & Spiders | NATURE / Reference Classification: LCC QL567.1.A1 C364 2023 (print) | LCC QL567.1.A1 (ebook) | DDC 595.79/9097--dc23/eng/20221007 LC record available at https://lccn.loc.gov/2022045093 LC ebook record available at https://lccn.loc.gov/2022045094 British Library Cataloging-in-Publication Data is available Editorial: Robert Kirk and Megan Mendonça Production Editorial: Karen Carter Text Design: D & N Publishing, Wiltshire, UK Jacket/Cover Design: Benjamin Higgins Production: Steven Sears Publicity: Caitlyn Robson and Matthew Taylor Copyeditor: Lucinda Treadwell Jacket/Cover Credit: Photograph by Joseph S. Wilson This book has been composed in Scala Pro (main text) and Scala Sans Pro (headings and labels) Printed on acid-free paper. ∞ Printed in China 10 9 8 7 6 5 4 3 2 1

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Dedications

Joseph

To my family, the best bee crew around.

Olivia

To Dennis, Eleanor, and Katherine.

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His labor is a chant, His idleness a tune; Oh, for a bee’s experience Of clovers and of noon!

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—EMILY DICKINSON

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CONTENTS Introduction

9

Protoxaea114

A Quick Reference Guide to Bees of Western North America25

Calliopsis115

Halictidae34 Augochlorella36 Augochloropsis38 Agapostemon40 Halictus46 Lasioglossum55 Sphecodes66 Dieunomia68 Nomia71 Conanthalictus74 Dufourea75 Micralictoides79 Xeralictus80 Colletidae82 Caupolicana83 Colletes85 Hylaeus90 Andrenidae97 Ancylandrena99 Andrena101

Macrotera118 Panurginus121 Perdita123 Protandrena141 Melittidae147 Hesperapis148 Macropis151 Melitta154 Megachilidae156 Ashmeadiella159 Chelostoma165 Heriades168 Hoplitis170 Osmia176 Protosmia188 Coelioxys189 Megachile194 Dioxys206 Anthidiellum209 Anthidium211 Dianthidium216

Megandrena112

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Paranthidium220

Apis299

Stelis222

Bombus301

Trachusa224

Nomada317

Lithurgopsis227

Townsendiella320

Apidae230

Epeolus322

Xylocopa233

Triepeolus325

Ceratina238

Ericrocis328

Diadasia243

Holcopasites330

Ancyloscelis249

Melecta332

Eucera251

Zacosmia335

Martinapis262

Brachymelecta336

Melissodes265

Neolarra338

Svastra272

Oreopasites339

Anthophora275 Habropoda284

A Key to Bee Genera in Western North America342

Anthophorula290

Glossary384

Exomalopsis292

Selected References391

Centris294

Index403

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INTRODUCTION

  9

Though they are minuscule across a large landscape, bees are essential pollinators inhabiting a wide range of ecosystems—from our cultivated and tended gardens, to the fields full of opportunistic weeds we see in abandoned urban lots, and the uninhabited and remote places where wildflowers flourish. When we think about the busy bees, most of us picture the nonnative honey bee (a managed labor force introduced from farms and fields overseas), but the honey bee represents the smallest fraction of North America’s hard-working pollinators. The most effective pollinators are native bees—those that evolved in concert with the natural ecosystems of this continent. North America’s native bees are diverse, widespread, and beautiful. While many species are rarely encountered, a handful are abundant and commonly seen in natural and urban settings alike. Identifying these diminutive flower visitors can be difficult even for the trained professional, but learning what species of bees make up a community can reveal a varied and highly connected network of individuals working together—sharing, and yet competing for, floral resources. There are an estimated 20,000 to 30,000 bee species on Earth. Around 20,000 of these species have been named and described. While bees have now been documented in every country, there are many ecosystems and habitats that have not been thoroughly studied; in these areas the potential for discovering new species is high. In the U.S. and Canada there are somewhere between 3,500 and 4,000 species; conservatively then, 10% to 18% of the world’s bees occur in these two countries. Species, as a taxonomic unit, are grouped together into genera according to morphological characteristics they have in common. Currently, bee genera are being reorganized, and the number of genera in North America seems to vacillate around 110 as some groups are split, and others are joined together. Of those, roughly 105 are found in western states; fewer than half a dozen are restricted to the east. The exact number of species occurring in the West is unclear; species names are in flux, and a line defining “The West” differs among geographers. Nonetheless, it is clear that bee species richness is incredible in western states. California has more than 1,600 recorded species; Arizona and New Mexico likely have more than 1,100 each; Colorado, Utah, and Nevada have more than 900 each. It would be fair to estimate that in all states west of the Rocky Mountains there are more than 3,000 species, with more if midwestern states are included. This guidebook is an introduction to some of the most frequently seen species in the western regions of North America, focusing on habitats west of the Rocky Mountains but also including the Great Plains, New Mexico, and West Texas. Although it does not cover all 3,000 western species, our hope is that it will provide the bee enthusiast with a tool to aid in the discovery of the rich bee fauna that exists all around us—a community of energetic insects visiting the flowers in our gardens and facilitating their transformation from blossoms to seeds, fruits, and vegetables.

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10  IS THIS A BEE?

IS THIS A BEE? While bees are common across most landscapes, differentiating a bee from other insects is devilishly difficult when watching an insect in flight. This difficulty is due, in large part, to two facts: (1) Bees and wasps are close relatives and still share many genes, which results in many structural similarities in how they look, and (2) many kinds of insects have evolved to resemble bees (and wasps) in order to fool potential predators into thinking they are able to sting. Bees and certain groups of wasps are especially challenging to distinguish. Generally, wasps, including yellowjackets and hornets, have less hair, have a slimmer waist, and have slenderer legs with spines on them. Bees, in contrast, usually have more hair, a thicker waist, and stouter, shorter legs; many also have pollen-collecting hairs on their legs. There are, of course, exceptions, and some bees are nearly bald, while some wasps are robust and relatively hairy. Some wasps can be separated from bees based on the silvery hairs on their faces; this is not a character that applies to all wasps, but it can be useful for ruling out some. In addition, most nonparasitic wasps lack branched hairs anywhere on their bodies, while bees always have branched hairs somewhere. Another reliable feature, though very difficult to see without a microscope, is the shape of the hind basitarsus, which is flattened in all bees, even cleptoparasites and males, and cylindrical in all wasps. One (somewhat) reliable way to differentiate between bees and their wasp cousins is to pay attention to behavioral cues. For example, bees and wasps have markedly different diets. Bees provision their nests with pollen as the protein source, but wasps provision with meat (often other insects). Bees, therefore, spend more time on flowers collecting pollen while wasps are casual floral visitors, stopping for a sip of nectar before returning to the hunt. These dietary differences have led to the evolution of some physical differences as well, such as pollen-collecting hairs on bees and spiny legs on wasps to assist in carrying prey. Of course, just as there are exceptions to using Compared with bees, wasps often have less hair, a skinnier waist, and skinnier legs with spines on them. mud dauber wasp

paper wasp right:

Yellowjacket

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Bees, like this Svastra, often have more hair than wasps, a thicker appearance, and thicker legs (often with pollen-collecting hairs on them).

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AN OVERVIEW OF BEE BIOLOGY  11

Bee-mimicking flies, like this hover fly, have larger eyes and shorter antennae than bees. They also have skinny legs and only two wings while bees have thick legs and four wings.

physical characteristics for identification, there are some exceptions to employing these dietary preferences as identification guides. For example, there are some wasps that feed their offspring pollen and at least one group of bees that is known to feed its progeny dead animal flesh (the latter does not occur in North America). While flies are not closely related to bees, many have evolved to look like bees, at least at first glance. Fortunately, there are simple ways to distinguish flies from bees. First, flies (especially those that look like bees) have larger eyes than bees. The eyes of the fly fill most of its head, while bee eyes are more widely separated, giving the appearance of a forehead (exceptions would include male honey bees and some male bumble bees). Second, most flies have short antennae, while bee antennae extend at least to the back of the head. These two distinguishing characteristics are often enough to tell the two apart. Other differences are seen in the legs and wings—flies tend to have smooth skinny legs while bees have thicker legs, often with pollencollecting hairs, and flies have two wings while bees have four.

AN OVERVIEW OF BEE BIOLOGY THE BEE LIFE CYCLE. Because we see bees flying among flowers on a warm day, we might assume that most of a bee’s life is spent tiptoeing through the tulips, so to speak. In fact, the greater part of a bee’s life is spent out of sight, sealed up inside a nest that was built by its mother, or, in some cases, by its sisters. Most bees live for just one year. For three to six weeks of that year they can be seen harvesting pollen from flowers; but the rest of the year is passed in relative darkness, inside a nest cell, undergoing a variety of developmental changes. With a life history more commonly associated with butterflies and beetles, bees are holometabolous, meaning they go through a complete metamorphosis. They begin life as an egg that subsequently develops into a larva (similar in appearance to a grub or maggot). This bee larva morphs into a pupa; a pupa may even be enclosed in a cocoon. Finally, the bee completes its life cycle after pupating, and emerges from the nest as a winged adult. WHERE DO BEES LIVE? Unlike the ubiquitous honey bees that live socially in large hives, most bees are solitary, meaning a single female bee builds a nest, by herself, for her offspring. A majority of North American native bees nest in holes in the ground, dug by the female that intends to use it. Other bees nest in preexisting holes like abandoned beetle burrows in dead trees, tiny holes in rocks, or even in snail shells. Some cavity-nesting bees excavate their own tunnels in rotting wood, pithy-centered plant stalks, or even solid wood. And a few bees construct nests on the outside of rocks or branches using pebbles and gravel mixed with resin, mud, or plant material to

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12  AN OVERVIEW OF BEE BIOLOGY

above:

  A Nomia entering her ground nest right:  A Megachile carrying a leaf to line her nest located in a hole in a piece of wood

build small enclosures. A female bee constructs a nest, then provisions the brood cells within it with pollen and nectar for her offspring. Internal nest architecture is variable among bee species and may differ markedly even among those of the same genus. WHAT DO BEES EAT? Adult bees drink nectar from flowers and eat some pollen for protein. Most female bees have groups of specialized pollen-collecting hairs on their legs or abdomen, which form structures called scopae (singular: scopa); note that placement of these hairs or even their color can help in bee identification. However, one genus (Hylaeus) collects pollen and nectar in its crop (an internal pouchlike structure between the throat and stomach), carrying her harvest home inside her body. This genus has no scopal hairs. Cleptoparasites also lack scopal hairs; see below for more information. Pollen-collecting bees stock their nest cells with a mixture of pollen and nectar to sustain their offspring as they develop over the months to follow. Many bees collect pollen from a wide assortment of flowering plants, not limiting themselves to any particular flower group. These bees are referred to as generalists, or polylectic bees. Dietary preference is on a spectrum, however, with some generalists visiting seemingly any flowering plant, while other generalists limit themselves to a narrower list of plant groups. At the opposite end of the spectrum are specialists: bees that are more particular about the flowers from which they collect pollen. These bees are called specialists, or oligolectic bees. The relative richness of specialist bees compared with generalists varies from region to region. In the eastern states a quarter of all bees are specialists, while in the West the total number is probably closer to 35%. In more local faunal studies of desert regions in the West, the proportion may rise to nearly 50%. Just as there is a range of foraging preferences among generalists, specialists may visit one genus or one family of plants when collecting pollen to feed to their offspring, or they may forage from a wider array of closely related plants.

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AN OVERVIEW OF BEE BIOLOGY  13

A Diadasia species that specializes on cactus flowers, foraging in a prickly pear flower

Cleptoparasites Among bees, there exist genera known as cleptoparasites that have evolved to usurp the pollen of other bees for their offspring instead of collecting their own. They find their way into the nests of their hosts and lay an egg discreetly. Some adult cleptoparasites kill the host egg when they find it in the nest. In other groups, when the parasitic egg hatches, it kills the host larva. Either way, the cleptoparasitic larva ingests the pollen meant for the larva of the host bee (hence the name “clepto,” emphasizing the stealing of the pollen). Around 10% of bees in the U.S. and Canada are cleptoparasites; most are in the Apidae bee family, where more than 25% of species fall into this category. Interestingly, cleptoparasites tend to be host specialists. Each cleptoparasitic genus has a preferred host genus in whose nests it leaves its eggs. Due to their unique life history, cleptoparasites may look different from pollencollecting bees. They are usually much less hairy than pollen-collecting bees and are thus more likely to be confused with wasps. In many, there are body parts with red coloring. While in general, their major body parts are the same, some structures are more developed than in nonparasitic bees, while other structures are less so. The specific characteristics and appearance of these structures are discussed in the sections of this book devoted to those genera.

Sociality Bees range widely in their preferences when it comes to neighbors and roommates. At one extreme are solitary bees, where females live and work in isolation, building and maintaining a nest entirely on their own. When these females finish providing for all their offspring, they die. The next generation, their sons and daughters, will never meet their mothers. Some solitary bees may be gregarious, nesting in aggregations of half a dozen to several hundred bees, each of which makes her own nest in which to leave her offspring. Other solitary bees may be communal; they share a nest entrance, but within the nest each female builds her own nest cells and fills them with her offspring and food stores. And finally there are eusocial bees. These are the groups of bees that cooperate to care for their young, divide up tasks related to colony persistence (foraging, nest

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14  AN OVERVIEW OF BEE ANATOMY

maintenance, etc.), and have rolling membership such that new bees meet the generations before them. Only the nonnative honey bee in the U.S. and Canada exhibits this level of cooperation among individuals. Its colonies persist for multiple years. Also social, but with less social organization and annual colonies instead of perennial, are the primitively eusocial bumble bees (see chapter on bumble bees for more). Finally, some sweat bees (Halictus) exhibit social behavior (see chapter on Halictus for more).

co

AN OVERVIEW OF BEE ANATOMY The adult bee body is geared toward very specific tasks. In males, the task is procuring a mate, while in females it is building a nest, and providing offspring with the pollen and nectar they need to mature to adulthood. As with all insects, the adult form has a head with antennae and mouthparts, a thorax with six legs, and an abdomen. Like most insects, bees also have two pairs of wings, compound eyes, and ocelli.

thorax

forewing

head hindwing

antenna

abdomen

foreleg

midleg

A Nomia showing the three parts of a bee’s body: the head (with antennae), the thorax (which includes the wings and legs), and the abdomen.

hind leg

A few words are commonly used to identify bee structures that aren’t encountered in regular conversation and should be defined here. These words will be used throughout the book. A carina is a thin raised line on a hardened body part. In essence, it is a razor thin ridge. Dorsal refers to the topmost surface. Ventral is the underside. Posterior refers to the back side of a structure, while anterior refers to the front side. Basal refers to the beginning of a segment (the base), and apical refers to the tip (the apex) or end of a body part.

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AN OVERVIEW OF BEE ANATOMY  15 simple eyes (ocelli) supraclypeal area

antennal sockets

subantennal sutures

epistomal suture

comp0und eye antenna

scape pedicel flagellomeres 2 1 3 4 5 6 7 8 9 10

paraocular area

clypeus

A Ceratina face showing the location of the large compound eyes, the simple eyes (ocelli), the antennal sockets and the antennae, the clypeus, epistomal suture, and subantennal sutures. The paraocular area and supraclypeal area are also marked. In some bees, the epistomal suture is strongly angled on each side and may even create lobes in the paraocular area that extend into the clypeus.

A female Agapostemon face with the antennal segments. Closest to the bee’s head is the scape, followed by the pedicel, which tends to be shorter than any of the flagellomeres. Next are 10 or 11 flagellomeres; typically, males have 11 flagellomeres and females have 10.

The head is made up of a series of plates that come together at seams, called sutures. The number and shape of the sutures can be important for bee fovea identification. Bees have two sets of eyes. There are two compound eyes, on the sides of the head, that are used to see An Andrena face showing the foveae, which are color, shape, and movement. On the top shallow depressions next to each compound eye. of the head are three simple eyes (ocelli) In Andrena the foveae are filled with thick appressed hair. that sense light and dark. The ocelli help the bee orient with the sun and sense changes in light and dark. Between the two compound eyes are the antennal sockets from which emerge the antennae. The antennae are composed of multiple segments, with the scape at the base followed by the pedicel and several flagellar segments called flagellomeres (males have 11 flagellomeres and females have 10). Areas of the face are named to aid in identification. The gena is the area behind the eye, before the head curves posteriorly. The preoccipital region generally refers to the area behind the gena, once the head has curved to the back, and the curve itself is called the preoccipital ridge. The malar space is the area between the lower margin of the compound eye and the base of the mandible. The foveae are shallow depressions on the faces of some bees next to the upper inner margin of the compound eye, which may be filled

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16  AN OVERVIEW OF BEE ANATOMY

with thick hair or may be bare. The clypeus is the more or less hexagonal plate that makes up the lower portion of the bee’s face. Between the clypeus and the compound eye is a triangular region called the paraocular area. Between the antennae is a region called the supraclypeal area. The frons is the space above the antenna, running up to the vertex, which is the top of the head. The mouthparts, including the mandibles, are often tucked under the bee’s head and are hard to see. If these mouthparts are extended, however, they contain useful information for bee identification. There are two mandibles, hinged just below the compound eyes. The apex of the mandibles at the front of the face contains the bee’s “teeth.” The overall shape, width, and number of teeth are distinctive between genera, as are the grooves and ridges on the outermost surface of each mandible. Finally, there is the tongue, or proboscis, which subantennal is made up of a number of smaller sutures pieces. When not being used to construct a nest, or probe flowers, it is folded up under the body. The labrum base of is the plate, hinged to the clypeus, the clypeus that, when folded under, covers the other mouthparts. The tongue itself is epistomal clypeus suture called the glossa. The glossa can vary apical margin significantly in shape, from long and of the clypeus above:

The shape of the clypeus and the grooves around this more or less hexagonal plate can be diagnostic for telling different bee groups apart.

preoccipital ridge vertex

left:

frons

comp0und eye malar space

A Halictus face showing various parts of the head that can aid in identification. These include the gena, preoccipital ridge, malar space, clypeus, frons, and vertex. The length of the malar space is measured from the bottom of the compound eye to the base of the mandible, and is the shortest distance between the two; its width is the same as the width of the base of the mandible.

clypeus

mandible gena

right:

A Megachile face showing mandibles with the teeth, which can be useful for identification.

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mandibles

teeth

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AN OVERVIEW OF BEE ANATOMY  17

labrum

galea

1 labial palpi (1–4)

2 3

4

prementum galea 1 4

2 3

labial palpi (1–4)

The tongue and some of the mouthparts of a Chelostoma, a long-tongued bee. Notice that the labial palpi have the first two segments elongated and flattened—they are much longer than the second two segments, which are angled to the side just slightly. A few bees have more than four labial palpi. Also shown in this picture is the labrum, which is a long plate that folds up underneath the clypeus. When folded up it is hard to see unless you look underneath the bee (this is unfortunate because the shape of the labrum can aid in identification). The galea are two sheaths that fold around the glossa (the tongue), which is hidden between them in this picture.

The tongue and some of the other mouthparts of a Perdita, a short-tongued bee. While the tongue does not look particularly short, the first and second segments of the labial palpi (one set on either side of the bee) are the same length as the second two (numbered 1–4). Compare this with the long-tongued bee tongues in the previous image. Also shown is the prementum (the beginning of the glossa), the glossa, and the galea (two parts, one on either side).

glossa

(Photos courtesy USDA-ARS Pollinating Insects Research Unit)

pointy to short and lobed; it may be brushy or smooth. The galea are two sheaths on either side of the glossa that more or less close over it when it is retracted. Connected to the top of the glossa are the labial palpi. They can range in number from one to six, and the length and number of these is one of the main ways to distinguish between long- and short-tongued bees. The thorax is also made up of joined plates (sclerites). The shape of the edges of the plates and the degree to which they are polished are important identifying features. The dorsal surface, the largest plate making up the thorax of the bee, is the scutum. Two shallow grooves are usually visible on either side of the center of the scutum. These are called parapsidal lines. On either side of the scutum are two small covers for the connecting point of the wings, referred to as tegulae (singular: tegula). The lateral edges of the scutum may be drawn out into points referred to as axillae (singular: axilla). Behind the scutum is the scutellum, a small C-shaped plate. Behind the scutellum is a plate called the metanotum. Behind, or posterior to, the metanotum, facing the abdomen, is the propodeum, which has two faces, one dorsal, and one posterior (facing the abdomen). The propodeum is, in truth, the first

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18  AN OVERVIEW OF BEE ANATOMY

scutum tegula scutellum metanotum propodeum propodeal pit

above:

Dorsal view of the thorax of a Halictus. Major plates used in identification are labeled.

Side view of the thorax of an Augochloropsis. Major plates used in identification are labeled.

pronotum

scutum scutellum

right:

pronotal lobe

mesepisternum episternal groove

scrobal groove

segment of the abdomen. At its center is the propodeal pit, a noticeable indentation in the surface of the exoskeleton. From the side, the structure supporting the front of the scutum is called the pronotum, and the lateral-most protrusion on this plate is called the pronotal lobe. The ridge that runs from the pronotal lobe up to the dorsal surface of the bee is the dorsolateral angle of the pronotum and is useful in identifying some bees, as is the pronotal collar, a ring of material that may extend from the dorsolateral angle toward the head. The edge that separates the transition from the anterior face of the thorax to the lateral face is termed the omaulus. Behind the pronotum is the mesepisternum, which has two grooves in its surface that are of interest. They are referred to as the episternal groove, and the scrobal groove, with the former occurring above (dorsal to) and forward (anterior of ) the latter. The scrobal groove runs perpendicular to the episternal groove, when the episternal groove is present. The wings are made up of veins and cells. Although the wings of most bees have the same cells, the shape and size of those cells and veins in relation to each other can be used to identify the bee.

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AN OVERVIEW OF BEE ANATOMY  19 mc

stigma

The fore- and hindwings of a Halictus. submarginal cells 3 2 1 prestigma The forewing is the larger wing, and 2r nearer the head. Important veins and 1r b spaces are colored. In blue are, moving from the body out, the prestigma, the stigma, and the marginal cell (mc). The tip of the marginal hamuli cell is sometimes squared off, and the entire cell may be extremely short, or very long and tapering. The stigma is the dark area on the bee’s wing jugal lobe adjacent to the marginal cell. While it is very noticeable on vannal lobe this wing, it is sometimes very small. The prestigma is often narrow, but in some bees it is very wide. Different bee genera may have one, two, or three submarginal cells. The submarginal cells are named (first, second, and third) from the one closest to the body and working out. The relative widths of these cells in relation to each other is an important feature of many bees. In green is the basal vein (b). In this bee it has a distinct arc; other bees have a straight basal vein. The red vein at the outside edge of the wing is called the second recurrent vein (2r). Its shape and how much curve it has are also important. Closer to the body is the first recurrent vein (1r). Where it intersects with the submarginal cells can be telling. At the front edge of the hindwing are tiny hooks (hamuli) that attach the hindwing to the forewing. Finally, there are two important lobes at the back edge of the hindwing: the jugal lobe (entirely missing in some bees) and the vannal lobe.

The legs are configured as three pairs: forelegs at the front, midlegs in the middle, and hind legs in the back. These legs are each composed of a series of segments, and the size and shape of each can be important for identification. Many female bees carry pollen on their hind legs; the placement and style of the scopal hairs they use to hold the pollen grains can vary substantially between genera, and even species. The abdomen also consists of many small segments. When working with bees, it is helpful to know that males have seven exposed abdominal segments, while females have six exposed, with the seventh always hidden. Considering that insects at large are made up of a series of segments, which are homologous across groups, it is technically the case that the first segment of the abdomen is incorporated as the last tibial The hind leg of an anthidiine, which carries spine pollen on the underside of its abdomen. basitarsus Identified from the end closest to the body w(the base) to the apex, the distinct sections are the coxa, the trochanter, the femur, the tibia, and the tarsal segments (the segment closest to the tibia is the basitarsus and is often much longer than the others). There may be an tarsus tibial additional little pad between the spurs tarsal claws known as the arolium tarsal claws (not shown). On the tibia, there is often a basitibial plate at the end closest to the femur. At the apex of the tibia are the tibial spurs, which vary in length, shape, and sometimes number. Every hair, spine, and specially curved surface hints at the life history of the bee.

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tibia

coxa

femur

trochanter

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20  AN OVERVIEW OF BEE ANATOMY

section of the thorax (the propodeum, discussed above). Thus, it can be difficult to accurately name bee body parts—is it more helpful to refer to the natural breaks in the structure of the body? Or to the anatomical structure from which they are derived? For this reason, some scientists refer to the abdomen as the metasoma, and the thorax as the mesosoma. For simplicity, we refer to the abdomen as the last large body segment of the bee, and to distinguish between each segment, we follow the format used by other bee taxonomists and number each segment, beginning with 1 for the segment closest to the thorax. The dorsal, or top surface of the abdomen is a series of plates called tergites, or tergal segments. And the first tergal segment is called T1. The apical edge of each tergite rests over the base of the tergite that comes after it. On the ventral surface, or underside, of the abdomen are matching plates called sternites or sternal segments that also overlap each other. The resulting effect is similar to a collapsing camp cup or a pocket telescope, where each section folds into and under the one before it. Of particular interest in the collection of tergal segments is T1 because it has an anterior surface, which faces the thorax, and a dorsal surface that points upward. The transition of this surface from anterior to dorsal often comes with interesting ridges or carinae and other features that can be used for identification. Also important are the hair bands on the tergal segments. The color, length, and placement of hair bands can contribute much to bee identification. At the apex of T5 in females is the prepygidial fimbria, which is a dense band of hairs, quite different in texture from other abdominal hairs, running its width. At the apical end of the abdomen is the pygidial plate, a flat plate, often surrounded by an easily seen ridge. On T6, on either A male Hoplitis, with the tergal segments (sometimes called tergites) numbered. Because the segments telescope in on each other, the last several may be hard to see. Many important distinguishing features are found on the first one, which has two parts—the front (anterior) side, which faces the thorax, and the top (dorsal) side, which faces up.

T1

T2

T3 T4 T5 T6 T7

S1 S2 S3

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S4

S5

S6

The sternal segments of a female bee. These are in general difficult to see because they run underneath the edges of the tergal segments. The back rims of the sternal segments sometimes have features on them that are important for distinguishing between species.

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AN OVERVIEW OF BEE ANATOMY  21

The pygidial plate of a Eucera

{1_1_1

side of the pygidial plate are the pygidial fimbria, dense hairs thought to be used in nest construction. The pygidial plate is on T6 in females, and on T7 in males (and thus, not as easily seen in males). pygidial fimbria The sternal segments follow the same numbering system as the tergal pygidial plate segments. Some female bees collect pollen on scopal hairs on the underside of their abdomens instead of on their legs. The color, length, and positioning of these sternal scopal hairs can be important to bee identification. Determining the sex of a bee: Distinguishing male bees from female bees is a simple matter for most individuals, though there are some cases where it requires a closer look. If scopal hairs are large and full of pollen, so that they can be easily seen on the abdomen or legs of the bee, the female designation is easy. Scopal hairs may be on the femur, or the tibia; be sure to look for long hairs in both areas of the hind leg when using this feature. However, if scopal hairs are not robust or otherwise easy to see, other features can be used. Males have 13 antennal segments, while females have 12. What’s more, the 13 antennal segments are often elongated, so that the antennae extend further on males than on females of the same species. In many genera, males have more yellow on the face and legs compared with their female counterparts. Males usually have one more visible tergal segment (seven) than females (six). However, sometimes tergal segments retract, so that the bee may appear to have fewer than the true six or seven; as a result this character is not always an easy way to distinguish male from female bees. Finally, and perhaps easier to see, female bees possess a sting, which male bees do not. Body Forms: Bee bodies can look very different from each other when the hair is removed and they are seen as silhouettes. Some are stout and stocky, while others are long and slender. These body forms are named after the most common genus that exhibits that form. Andreniform bees have the form of an Andrena: slender, with an oval abdomen that rounds or tapers at either end. Euceriform or anthophoriform bees have the form of Anthophora or Eucera: robust head, thorax, and abdomen, and often very hairy. Megachiliform bees have the form of Megachile or Anthidiini: thick round head, stout thorax, and wide abdomen.

Andreniform

Euceriform or anthophoriform

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Megachiliform

Bees are often described based on the overall shape of their bodies. Andreniform bees are slender, with an oval abdomen that rounds or tapers at either end. Euceriform or anthophoriform bees have a robust head, thorax, and abdomen and are often very hairy. Megachiliform bees have a thick round head, stout thorax, and wide abdomen.

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22  USING THIS BOOK

USING THIS BOOK This book will address species commonly found west of the Rocky Mountains, with a particular focus on bees west of the Great Plains. A few rare species that occur in Texas and the Midwest have also been included. Because there are more than 3,000 bee species in the West, including them all in this book is not practical. Instead, we focus on the common and the unique species. As you use this book to identify the bees around you, remember that bee identification requires patience, even for trained bee scientists. We hope that this book will serve as a springboard to recognizing the bees you see and will help you appreciate the incredible diversity of bees that live in western North America. There are several ways to tackle the challenge of identifying small bees. The most reliable way to determine a bee’s identity is to capture it using a net or some other tool, euthanize it, and pin it. Species determination can then be done using a microscope, taxonomic keys, and/or a reference collection. This level of effort and equipment may be beyond the capability of many, as microscopes, pins, and storage containers are expensive, and access to reference collections is limited. Should the bee enthusiast choose to make their own collection, we refer you to a number of sources listed at the end of this book that outline how to collect, euthanize, and preserve specimens. Alternatively, bees can be photographed, as they root around, unaware, in flowers. They can also be captured and chilled for a few hours in a refrigerator or cooler, then photographed prior to release. Many characters that can aid in the identification of a bee to genus level, and even to the species level, can be seen from crisp images taken with modern digital cameras or even with smartphones. It is best to take photos of the bee from several angles, and to include as many of the body parts as possible. Wing venation is useful in determining or distinguishing between some closely related genera. Legs can offer additional clues, especially in females, as different species carry pollen on different sections of the leg. The abdomen is important because the number, color, length, and position of stripes can be telling. The thorax may be shiny or densely punctured and may have interesting projections or other sculpted contours that are important. And finally, the general shape of the face, the facial markings, the presence or absence of hair, and the position (and length) of the antennae are important identifying features. Setting a camera to a continuous shooting mode (also called burst mode, sports mode, or continuous high-speed mode) can help—in the age of digital photography, redundant and out-of-focus images can easily be deleted after being viewed. For the serious bee photographer, we recommend a 100 mm or greater lens and 10 megapixels or more (so that photos can be zoomed while shooting or cropped afterward). Another way to take photos of bees for identification purposes is to collect them using a net, transfer carefully to a small container, and chill in the refrigerator or a cooler for at least five to ten minutes, and up to several hours. The bees will enter torpor and can be photographed without the risk of blurring the image and can be turned and staged for optimum photographic capture of their various identifying

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USING THIS BOOK 23

Taking photos of a bee from several angles can aid in identification.

features. After a few minutes they will return to normal and will fly away. In addition, specimens can be briefly netted and placed in transparent vials for viewing with a loupe or hand lens before being released. With practice, common bees can be identified in the field without the aid of photos. Familiarity with what is in a given area is particularly helpful, so time and dedication are key. It can be daunting as a beginner to know where to begin with bee identification. We recommend that beginners start at the beginning: familiarize yourself with bee terminology and read the sections in this book that highlight bee family characteristics. This book can be used to aid in identification in several ways:

— Flip from page to page looking for a matching group of bees and then read the detailed identification characteristics to determine if the bee is a match.

— Use the taxonomic key at the back to arrive at the correct family and genus. — Use the “quick reference” guide for bees that appear fairly distinctive. We have sorted the bees included here taxonomically, so that successively larger groups share more characteristics. For example, all members of the Andrenidae bee family have two subantennal sutures. Within this family, all bees in the tribe Andrenini have (in addition to two subantennal sutures) thick facial foveae. And within the tribe Andrenini, all members of the genus Andrena have (in addition to subantennal sutures and thick facial foveae) a hind basitarsus that is more than half as long as the hind tibia. You will find family descriptions and tribe descriptions that highlight characteristics shared by the genera within. Our summaries for genera are divided into the following sections: 1

2

AN OVERVIEW that lists general life history characteristics for the genus, including specialist or generalist tendencies, nesting preferences, and what is known of the genus’s characteristic sociality. IN THE WORLD, which outlines the distribution and abundance of species (see the glossary for a description of terminology used here).

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24  USING THIS BOOK

3 CLEPTOPARASITES, listing known cleptoparasites for each genus—likely to be seen in concert with their host species. 4 IDENTIFYING FEATURES of the genus, including similar genera that might deserve a look for comparative purposes. For each species, we list body size, phenology, floral hosts, range, and nesting habits followed by identifying characteristics in addition to those listed for the genus. For each description, we highlight the characters most useful for distinguishing the bee from other species, but do not include full body descriptions. We begin each description at the front of the body and move through to the abdomen (Head, Thorax, Wings, Legs, Abdomen). If there are no distinguishing or notable features on a body part, we do not discuss it. Unless stated otherwise, characters listed apply to both male and female bees of that species. We also list similar species, which may or may not be described in detail in this book. For the reader eager for more information, publications of interest can be found at the back of the book for each genus. Note that newer ones may require purchasing. Each bee species featured in this book has an accompanying range map, shaded from light green to dark green. Because the actual ranges for most bees are not well understood, we modeled the suitability of habitats in western North America for supporting each bee, based on verified locality records, correlated with temperature and rainfall patterns, across 1 km grid squares. For example, in the sample map shown here, the light green color for Bombus huntii in the Central Valley of California suggests a lower probability here that the appropriate habitat for this species occurs. In contrast, southern Idaho is a dark green, meaning that the habitats associated with this area are more likely to support this bee. The drawback to this approach is that it relies on verified historical locality records, and so it may be less accurate for rarer species, or for species whose ranges are experiencing contemporary shifts, for example, in response to climate change. To best understand the range of a species highlighted in this book, look at the map, and also read the range description in the text; any shade of green is indicative of potential bee habitat, and thus occurrence, for the species.

An example of the distribution maps shown throughout the book. Darker shades of green indicate a higher likelihood that the habitat is suitable for an individual bee species and lighter shades indicate a lower likelihood.

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A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA BEES THAT ARE COMPLETELY RED

Nomada (page 317)

BEES THAT ARE YELLOW AND BLACK

Anthidiini (page 209–227)

Perdita (page 123)

Nomada (pages 317–321)

Calliopsis, some species (page 115)

Andrena, some species (page 101)

Bombus (pages 301–317)

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26 A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA

Caupolicana (page 83)

Stelis, some species (page 222)

Protoxaea (page 114)

Habropoda (page 284)

Centris, some species (page 294)

Anthophora, some species (page 275)

Martinapis, some species (page 262)

BEES THAT ARE METALLIC GREEN OR BLUE

Osmia (page 176)

Augochlorini (pages 36–40)

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Agapostemon (pages 40–46)

Lasioglossum, some species (pages 55–66)

Hoplitis, some species (page 170)

Andrena, some species (page 101)

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A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA  27

BEES THAT HAVE A DARK THORAX AND RED ABDOMEN

Lasioglossum, some species (page 55)

Sphecodes (pages 66–67)

Xeralictus (page 80)

Andrena, some species (page 101)

Dieunomia, some species (page 68)

Micralictoides (page 79)

Calliopsis, some species (page 115)

Macrotera, some species (page 118)

Neolarra (page 336)

Dioxys, some species (page 206)

Ashmeadiella, some species (page 159)

Holcopasites (page 330)

Oreopasites (page 338)

Nomada, some species (page 317)

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28 A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA

BEES THAT HAVE LONG ANTENNAE

Male Lasioglossum (pages 55–66)

Male Eucerini (pages 251–275)

BEES THAT ARE DARK WITH LIGHT BANDS ON THE ABDOMEN

Halictus (pages 46–54)

Lasioglossum, some species (page 55)

Anthophorini, some species (pages 275–294)

Eucerini, some species (page 251)

Megachile, some species (pages 194–206)

Exomalopsini, some species (pages 290–294)

Osmiini, some species (pages 159–189)

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A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA 29

Colletes, some species (pages 85–90)

Many parasitic bees (pages 189, 322–330)

Lithurgopsis (page 227)

Andreninae, some species (pages 99–113)

Nomia (page 71)

Hesperapis (page 148)

Melitta (page 154)

Trachusa, some species (pages 224–227)

BEES WITH A TRIANGULAR OR POINTY ABDOMEN

Coelioxys (page 189)

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30 A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA

BEES THAT ARE EXTREMELY LARGE (BIGGER THAN THE TOP JOINT OF THE PINKY)

Bombus (pages 301–317)

Xylocopa (page 233)

Dieunomia (page 68)

Caupolicana (page 83)

Protoxaea (page 114)

Centris (page 294)

Eucera (Xenoglossa) (page 257)

Svastra, some species (pages 272–275)

BEES THAT ARE MINUSCULE

Lasioglossum, some species (page 55) Perdita (page 123)

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A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA 31

Conanthalictus (page 74)

Ceratina, some species (page 238)

Hylaeus (page 90)

Neolarra (page 336)

Oreopasites (page 338)

BEES THAT ARE VERY HAIRY

Apidae, many species (pages 230–341)

Andrena, some species (page 101)

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Ancylandrena (page 99)

Colletes (pages 85–90)

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32 A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA

Megandrena (page 112)

Caupolicana (page 83)

Protoxaea (page 114)

Megachile, some species (pages 194–206)

BEES THAT ARE SMALL AND DARK

Ceratina (page 238)

Osmia, some species (page 176)

Calliopsis (page 115)

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Panurginae (page 115–146)

Osmiini, some species (page 159)

Macropis (page 151)

Hylaeus (page 90)

Rhophitinae, some species (page 74)

Lasioglossum, some species (page 55)

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A QUICK REFERENCE GUIDE TO BEES OF WESTERN NORTH AMERICA 33

BEES THAT ARE LARGE AND DARK

Xylocopa (page 233)

Anthophora, some species (page 275)

Megachile, some species (page 194)

Osmia, some species (page 176)

Trachusa, some species (page 224)

Bombus, some species (page 301)

BEES THAT CARRY POLLEN ON THEIR ABDOMEN

Megachilidae (pages 156–229)

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34  Halictidae

HALICTIDAE

Halictidae are small to medium-sized bees, ranging from bright metallic green to matte black. Most species are abundant where they occur, with numerous individuals of the same species occupying an area. The majority of Halictidae in the U.S. nest in the ground, but a few are cavity nesters and can be found in rotting wood. Many Halictidae are polylectic, or generalists, though a few genera (Dufourea, Dieunomia) include species that are all specialists. A number of species exhibit some form of sociality, ranging from communal nesting, where multiple individuals share a nest entrance, to modest sociality (primitively eusocial), with a division of labor, and a queen and her subordinate daughters aiding in rearing the subsequent generations. IDENTIFICATION: Few features unite the Halictidae, but the arcuate basal vein on the wing is strong in most of the genera and can be a good character for verifying the family in many cases. Pollen is collected on the tibia of nonparasitic females. There is one subantennal suture. The tongue is short. Despite the difficulty of family level characters, many of the genera are distinctive in appearance and can be easily identified. Most Halictidae have an arcuate basal vein.

The distinct curve of the basal vein on the wing of most of the genera in Halictidae can be a good characteristic for verifying the family. TAXONOMY: The Halictidae are the second most speciose group in the U.S. In North America there are 18 genera in the Halictidae, and in the western parts of the U.S. and Canada there are 17 genera. These genera are divided into three subfamilies, and several tribes, outlined below:

—  SUBFAMILY HALICTINAE: Includes the most commonly seen and abundant Halictidae in North America. Females are andreniform, resembling Andrena in their body shape. Males are elongated with slender abdomens and long antennae. On the wing, the basal vein is strongly arcuate. — AUGOCHLORINI: In females, the apical margin of T5 is strongly notched. Distinctly green or coppery in color.

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HALICTIDAE   35

Augochlorella, Augochloropsis, Augochlora, Pseudaugochlora (the latter two are absent or rare in the west; not in this book). — HALICTINI: On the abdomen, in females, the apical margin of T5 has no notch in it. May be matte black, black and red, gunmetal green or blue, or brilliant green. Agapostemon, Halictus, Lasioglossum, Sphecodes, Mexalictus (rare southwestern bee; not in this book).

T5 of Augochlorini has a little notch in the middle.

—  SUBFAMILY NOMIINAE Includes the agriculturally important Nomia melanderi (alkali bee), which pollinates alfalfa. Differs in wing venation from the Halictinae in that the marginal cell is rounded and doesn’t taper much (the top and bottom margins remain parallel to each other). The middle of the three submarginal cells is significantly smaller than the first and third submarginal cells. The two genera look little alike, and both are unique among halictids in appearance. Dieunomia, Nomia

T5 of Halictini has no apical notch.

Marginal cell is rounded at the tip and does not taper much toward the apex.

Middle submarginal cell is smaller than the other two.

The wing of bees in the Nomiinae subfamily is distinct compared with Halictinae.

—  SUBFAMILY ROPHITINAE In western North America six genera occur. They are seldom seen but can be identified by the wide clypeus and low antennal sockets. All members of this genus are specialists.

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36  Halictidae

— R OPHITINI: Dufourea, Conanthalictus, Micralictoides, Xeralictus, Protodufourea, Sphecodosoma (the latter two genera are Bees in the subfamily rare, not in this book). Rophitinae have antennal sockets placed low on the face.

Within the Halictidae, there are 17 genera and more than 530 species.

Antennal sockets are low on the face, close to the clypeus.

AUGOCHLORELLA — SUBFAMILY: Halictinae — TRIBE: Augochlorini OVERVIEW: Augochlorella are small to medium-sized bees, brilliant green to red green or copper green. These bees can be solitary or social, depending on climate. All Augochlorella are ground-nesting, often occurring in dense aggregations. They are polylectic. IN THE WORLD: Sixteen species total. All are restricted to North, Central, and South America. Most abundant in Central and South America. In the U.S. and Canada there are seven species. Four species occur in the West and Midwest. CLEPTOPARASITES: Sphecodes. IDENTIFYING FEATURES: Small, petite green bees. HEAD: The inner margin of the compound eye is notched, just above the antennal sockets. On the clypeus, between the subantennal sutures and the compound eye (i.e., the lateral portion of the epistomal suture), the epistomal groove is at a right angle, but the paraocular area is not lobed. In males, the second flagellar segment is significantly Augochlorella shorter than the first. THORAX: The propodeum is (female) smooth, with no sharp ridge delimiting its border. The inner margin of the WINGS: The marginal cell is pointed. The basal vein compound eye is notched, just above the antennal socket. is strongly curved. ABDOMEN: Green in both males and females. In males, the apical margin of S4 is concave. SIMILAR GENERA: Agapostemon is similarly bright green but has a strong ridge running around the propodeum that is not seen in any of the Augochlorini. Also, the inner margin of the Augochlorella eye is notched, which is not the case in Agapostemon. Augochlorella looks similar to other Augochlorini genera. They can be distinguished by differences in the marginal cell, the clypeus, and the shape of the tegula (see those genera for clarification).

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Augochlorella  37

— Augochlorella pomoniella SIZE: Small; 7–9 mm. PHENOLOGY: May through November, longer in southern locations. FLORAL HOSTS: Generalist visiting a wide array of flowers. RANGE: California east to New Mexico, north through Utah and Nevada. NESTING: Nest in the ground on flat or slightly sloped areas, generally bare soil, often in clusters. IDENTIFICATION: Larger shiny bright green bee. HEAD: Brilliant green in both males and females. THORAX: On scutum, punctures are widely spaced Notch on inner margin over a smooth integument. of compound eye Dark brown Propodeum is relatively polished tegula and smooth. Tegulae are dark brown. LEGS: In males, green legs, rather than dark brown as in other species. ABDOMEN: In females, T1 is polished, and very bright. Punctation is fine and widely spaced throughout. In T1 is brightly males, the abdomen is dark polished. green with apical margins on T2–T3 slightly dull. Augochlorella pomoniella (female) SIMILAR SPECIES: Four Augochlorella species occur The propodeum in the western U.S., and they is outlined by a smooth ridge. can be difficult to distinguish. Augochlorella pomoniella is the most distinctive for its larger size and more brilliant and extensive green coloration. In terms of distribution, A. aurata is primarily an eastern species, The legs are Strong notch in metallic blue/green. but where it overlaps with compound eye A. pomoniella, the brick red tegula of A. aurata should be Augochlorella pomoniella (male) distinctive. Augochlorella neglectula and A. bracteata are both found along the border of Mexico and Arizona. They differ from A. pomoniella in that the pits and texturing on the scutum, scutellum, and propodeum are denser in those two species than in A. pomoniella.

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38  Halictidae

AUGOCHLOROPSIS — SUBFAMILY: Halictinae — TRIBE: Augochlorini OVERVIEW: Small to medium-sized brilliant green sweat bees. Nest in the ground and are occasionally primitively eusocial, with at least a few daughters of late-summer generations foraging while their mother remains home (other daughters venture off to start their own solitary nests). As such, population sizes grow over the course of the summer, and these bees are relatively abundant by midsummer to early fall. Augochloropsis are generalists, collecting pollen from any number of summer/ fall-flowering plants. IN THE WORLD: Worldwide, there are around 140 described species, mostly occurring in Central and South America. In North America there are three species; they are less common in western states than eastern. CLEPTOPARASITES: Sphecodes. IDENTIFYING FEATURES: Green bees, slightly larger than other Augochlorini in the West. HEAD: There is a notch in the inner margin of each compound eye. The epistomal groove does not angle sharply, as it does in other Augochlorini. THORAX: There is no carina outlining the propodeum. The pronotal lobe has a strong carina outlining it, which can be seen from a front oblique angle. The tegula is comma-shaped, metallic in color, with a clear indent on the inner margin. WINGS: Basal vein is arcuate. LEGS: In females, the basitibial plate is hardly visible at all. In both sexes the inner midtibial spur has wide parallel comblike projections. ABDOMEN: The first two tergal segments exhibit a thin row of sparse, stout hairs (this may wear off in older specimens). SIMILAR GENERA: Agapostemon is also green but has a strong ridge running around the propodeum that is not seen in Augochloropsis. Also, the inner margins of the compound eyes of Augochloropsis are notched, which is not the case in Agapostemon. Augochloropsis look similar to other Augochlorini genera. They can be distinguished by the clear presence of a basitibial plate in females of those groups, as well as differences in the marginal cell, the clypeus, and the shape of the tegula (see those genera for clarification).

— Augochloropsis metallica SIZE: Medium; 11 mm. PHENOLOGY: March through November. FLORAL HOSTS: Broadly polylectic. RANGE: Rare in western states; mostly Colorado, Nebraska, Texas, New Mexico, and Arizona. NESTING: Ground-nesting bee. Reports exist of this bee being solitary, communal, or social. IDENTIFICATION: Bright metallic green, in some geographic areas with blue highlights to the green colorations. Most features listed in characters for the genus.

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Augochloropsis  39 Augochloropsis species have a fringe of stiff hairs lining the apex of T1 and T2. Notch on inner margin of compound eye

Tegula is not a perfect oval and is slightly metallic.

The basitibial plate is so small as to be nonexistent in Augochloropsis.

Augochlora metallica (female)

Marginal cell ends bluntly.

Rows of bristles run across T1 and T2

Augochloropsis metallica (male)

Tibiae are yellow, but other leg segments are green.

Rows of bristles at the apex of T1 and T2, which have deep distinct punctures.

With Augochloropsis, the clypeus is only barely notched, not as in other Augochlorini.

HEAD: In males, mandibles and antennae may be black, at least in part. THORAX: Scutum shiny, with small punctures that become closer together toward the head and laterally. WINGS: Tegulae green along inner margin, brown toward outer margin. LEGS: In females, basitibial plate is greatly reduced. In males, tarsi are yellowish, but legs are otherwise green. ABDOMEN: Green in both males and females. In females T1–T3 with deep, distinct punctures. SIMILAR SPECIES: There are two subspecies of A. metallica: A. metallica metallica, and A. metallica fulgida. The differences between the two are notable enough that they may be designated as separate species at some point. A. m. metallica females are not very polished on T2, which has a distinct comb of flattened hairs across the apical edge. In males, the tergal segments are densely and finely punctate, and the propodeal triangle is roughened and not polished. A. m. fulgida is highly polished on T2, with large, well-separated punctures. The apical fringe of hairs on T2 does not look much different from other apical hairs on the abdomen. In males, the surface of the tergal segments, T2 included, are polished between punctures, and the propodeal triangle is polished.

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40  Halictidae

Augochloropsis metallica: note the more rounded lateral angles of the pronotum.

Augochloropsis sumptuosa: note the points on the lateral angles of the pronotum in this species.

Augochloropsis sumptuosa is the only other Augochloropsis that extends to the West. On the sides of the pronotum of A. sumptuosa are wide projections, which are very distinctive. Also, on the head, the vertex bulges, rising up above the ocelli noticeably when viewed straight on at the face.

AGAPOSTEMON — SUBFAMILY: Halictinae — TRIBE: Halictini OVERVIEW: Small to medium-sized bees commonly seen from mid-spring through late fall. All Agapostemon species nest in the ground. May nest solitarily, communally with many females using one hole, or in dense aggregations. May even nest among aggregations of other bees, including Halictus, Nomia, and Andrena. Nests can be in lawns, vertical banks, or shallowly sloped hills. Agapostemon are generalists, found on a variety of flowers. Males sometimes swarm around larger blooming shrubs, especially in the fall. Many species are bivoltine or multivoltine. Fertilized females overwinter, emerging in early spring. After foraging and nesting, they die. Their offspring are the late-summer/fall generation, with females of this generation emerging first, and males emerging in All Agapostemon have a strong ridge around the perimeter of the propodeum. early fall to mate with the females that will overwinter again, fertilized. IN THE WORLD: Agapostemon are found only in North, Central, and South America. There are 14 species north of Mexico. Eleven occur in western states. CLEPTOPARASITES: Nomada and Sphecodes. IDENTIFYING FEATURES: Agapostemon all have a brilliant green head and thorax. HEAD: Green in both sexes, but lower half

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Agapostemon  41

of clypeus yellow in males. No indentation along the inner margins of the compound eyes. THORAX: The perimeter of the propodeum is carinate, separating this genus from other metallic green Halictidae (see Augochlorini). WINGS: Basal vein is strongly curved. LEGS: The hind tibiae are very long—at least as long as all the tarsal segments of the hind leg together. Males have four tarsal segments on the hind legs, instead of the more typical five tarsal segments. ABDOMEN: In females the abdomen is usually green (but see A. virescens). Male individuals can be identified by the yellow-and-brown or black stripes running across the abdomen.

— Agapostemon texanus SIZE: Small

to medium; 9–11 mm. through October; multivoltine. FLORAL HOSTS: Polylectic. RANGE: Extremely widespread, occurring from southern Canada south through Costa Rica and from coast to coast. NESTING: Solitary; may be communal in some cases. Nests in a variety of soil types, and may be in flat areas, or vertical banks. Can occur in aggregations with other individuals, or even with other bee species (i.e., Halictus species). PHENOLOGY: April

Agapostemon texanus (female)

Agapostemon texanus (female)

Overall, the body of Agapostemon texanus is hairier.

IDENTIFICATION: Females have an overall hairy appearance, especially on the sides of the thorax, as well as covering the abdomen. This masks some of the hair bands on the abdomen, making them less distinct than in other species. HEAD: Bright green. THORAX: Bright metallic green. In females, punctures of two sizes lie on a shiny surface. LEGS: In males, on the hind leg, the inner face of the tibia

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Scutal punctures of two sizes: shallow and numerous, with a few larger deeper pits interspersed

Arcuate basal vein

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42  Halictidae T1 is black, anteriorly. Abdomen yellow and brown striped

Agapostemon texanus (male)

Femur is longer than it is wide, not appearing inflated.

Hind tibia usually with a dark spot or dark line running its length, often on both the inner and outer faces.

Agapostemon angelicus (male)

In male A. angelicus, hind tibia with a dark spot or dark line only on the inner surface, not the outer surface.

has a dark stripe or spot running from the femur to the basitarsus; often a mark on the outer face as well. ABDOMEN: In females, abdomen is green. In males, the yellowand-black-striped abdomen may appear lightly metallic, especially laterally, and S5 and S6 are yellow. SIMILAR SPECIES: In the western U.S., females of Agapostemon angelicus and females of A. texanus are indistinguishable. The shiny thorax, due to sparse punctation and polished integument, is characteristic. In males, the hind tibia of A. angelicus has black or brown markings on the inner surface (facing the abdomen), but not on the outer surface.

— Agapostemon femoratus SIZE: Small

to medium; 9–11 mm. PHENOLOGY: March through November. FLORAL generalist. RANGE: Southern Canada to Mexico, California to the Rocky Mountains. Found from sea level to more than 10,000 feet. NESTING: Nests are deep, often in compacted soil. IDENTIFICATION: Medium-sized green bee. Males with yellow-and-black-striped abdomen. HEAD: Green. In males, with a yellow band across the lower portion of the clypeus. Also in males, antenna yellow dorsally and darker brown ventrally. THORAX: The HOSTS: Broad

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Agapostemon  43

scutum and scutellum are very coarse. In females, scutum has punctures of uniform size without shiny integument in between. Also in females, the scutellum lacks punctation, being more corrugated than pitted. LEGS: In males, hind femur is hugely inflated. Hind basitarsus is also swollen and has a very large ridge at its base, and a groove at its apex. ABDOMEN: In females, white hair bands run apically across each green tergal segment. In males, there is no metallic tint to the sides of the yellow and brown tergal segments. SIMILAR SPECIES:

Agapostemon angelicus/ texanus look similar; females can be differentiated by the texture of the scutum (rough in A. femoratus, shiny between punctures for A. angelicus/texanus). The inflated hind femur in males is distinctive. Punctation on

thorax is coarse, but all one size. Agapostemon femoratus (female)

Agapostemon femoratus (male)

The hind femur is greatly enlarged.

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44  Halictidae

— Agapostemon melliventris SIZE: Small to medium; 9–11 mm. PHENOLOGY: March through December. FLORAL HOSTS: Broad generalist. RANGE: Mexico north to Idaho, Oregon, and southern Washington. West to California and (rarely) east to the Mississippi River. Most common in the southwestern deserts. NESTING: Nests in the ground in relatively deep nests. IDENTIFICATION: Medium-sized bee with green head and thorax. In females the abdomen is often honey colored with bands of white hair. Males with yellow-and-black-striped abdomens. HEAD: Green. In females, clypeus has a yellow stripe at the lower margin. Also in females the mandible has yellow at the base. THORAX: Bright metallic green The clypeus in both sexes. LEGS: In males, has a yellow stripe on it. hind leg is mostly yellow, with brown just at apex of femur and base of the tibia. ABDOMEN: In females, the terga are usually amber colored, with thick white stripes of hair. In males, the terga are mostly yellow, with brown markings restricted to thin bands. The first tergal segment has the anterior face completely yellow with no brown or black. Note that some populations—mostly in the Midwest (South Dakota south to Oklahoma)—have females with black terga instead. SIMILAR SPECIES: Agapostemon melliventris is the only species in which females have an amber-colored abdomen. Populations

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Agapostemon melliventris (female)

This is the only Agapostemon in which females have an amber thorax instead of a green or black one.

Abdomen is mostly yellow, with thin brown bands on each segment.

Agapostemon melliventris (male)

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Agapostemon  45

with a black-and-white abdomen resemble A. virescens, though the yellow lower rim of the clypeus in A. melliventris females is distinct. In males, the lack of maculations on the hind leg, and mostly yellow abdomen, should help distinguish from other species.

— Agapostemon virescens SIZE: Medium;

10–11 mm. through November. FLORAL HOSTS: Polylectic. RANGE: Widespread, occurring across the U.S., more common in northern states of the West than in southwestern states. NESTING: Usually nests in aggregations, and sometimes with multiple females using the same nest entrance. Nests may be in lawns, near gardens, or in disturbed areas. IDENTIFICATION: HEAD: In females, mandible base is dark yellow. THORAX: Bright metallic green. Covered in fine punctures, almost touching. Size of pits is wide-ranging, and scutellum may have pits of many different sizes. LEGS: In males, the hind femur is long and narrow, while the hind tibia is mostly Agapostemon yellow, with only a little bit of virescens (female) dark coloration at the joints. PHENOLOGY: April

Agapostemon virescens (male)

Strong ridge apparent around propodeum (as in all Agapostemon).

Abdomen is black, with white stripes instead of green, like other Agapostemon.

Femur is longer than it is wide.

Abdomen is yellow with brown stripes (or brown with yellow stripes?).

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Femur is longer than it is wide, not looking inflated.

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46  Halictidae ABDOMEN: In females, the abdomen is black, with white hair bands. There are no yellow markings on the sterna of males, though the tergal segments are yellow with brown stripes. Also in males, on S6 there is an oval-shaped depression with a ridge in the middle. SIMILAR SPECIES: There are three western species in which the abdomen of females is black. Agapostemon virescens is a predominantly eastern species that continues into northern states in the Midwest and West. Agapostemon coloradinus is more widespread throughout the West. More common in southern states, and can be difficult to distinguish from A. virescens. On the mandible, the base is dark brown to black in A. coloradinus. Agapostemon tyleri is rarer, occurring mostly in the Southwest. It differs from A. virescens in the pits on the scutellum, which are in two sizes only in A. tyleri, but are highly variable in A. virescens.

HALICTUS — SUBFAMILY: Halictinae — TRIBE: Halictini OVERVIEW: Small to medium, incredibly abundant brown to black bees. All Halictus nest in the ground, and many exhibit varying levels of sociality, even within the same species depending on the length of the flowering season. Because of their social lifestyles, Halictus species are often seen for a long period of the flowering season, rather than for a short window in the spring or summer. As such, they are all generalists. Halictus are one of a few bees that will land on humans and “lick” the salty sweat from their skin. IN THE WORLD: Found on all continents except Australia. Most common in Northern Hemisphere. Nearly 300 species are known. In western North America there are eight species. CLEPTOPARASITES: Sphecodes are common parasitic bees of Halictus. IDENTIFYING FEATURES: Some species may have light metallic green or copper hues, but the majority are matte black/brown. Males are long and slender, with long antennae The basal vein on Halictus specimens is strongly arcuate.

There are three submarginal cells separated by strong veins.

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Halictus  47

Each tergal segment ends with a band of white hair.

that reach to the back of the thorax. HEAD: The gena is usually thick, giving the head a bulky appearance. Male faces include yellow markings on the clypeus, and the legs may be yellow (or red) as well. WINGS: Halictus have the arcuate basal vein that is characteristic of many Halictidae. Veins that define the first, second, and third submarginal cells are strongly developed. ABDOMEN: The hair bands are apical, running across the end of each tergal segment. In worn specimens this may be less visible in the center, but the hair is usually still present on the sides. We cover characteristics for identifying the five most common species here. SIMILAR GENERA: Halictus look superficially similar to Lasioglossum. Though some Halictus species may exhibit lightly metallic colorations, they are never as prominently metallic as Lasioglossum subgenus Dialictus. The heads of Halictus individuals are thicker than those of Lasioglossum. The wings of Lasioglossum often have weak veins separating the submarginal cells, which is not the case with Halictus. And tergal hair bands in Halictus are apical, while in Lasioglossum, if present, they are basal. Andrena and Colletes may also bear some resemblance. The arcuate basal vein is useful in separating Halictus from these two.

— Halictus confusus SIZE: Small;

7 mm. PHENOLOGY: March through October. FLORAL HOSTS: Polylectic. the U.S. and Canada, as far north as northern Quebec, and northern Alberta. Also found in northern Europe and northern Asia. NESTING: Ground-nesting bee, often gregarious. Interconnected nests may have multiple entrances. LIFE HISTORY: Eusocial bee with annual colonies. One generation of mated queens (foundresses) overwinter, emerging between March and May and digging a new nest in the ground. They produce a brood of workers and some males that are mature by midsummer. RANGE: Across

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48  Halictidae

Some of these females retain the ability to make their own offspring, but some are sterile. All females nest together, with many passively provisioning nest cells for the queen’s eggs, while others are bullied by the larger queen into helping with her offspring. If the queen dies, one of these reproductively mature daughters will take over egg-laying. In the fall, males and the next year’s queens are produced. Therefore, this bee exhibits both univoltine and bivoltine life histories. IDENTIFICATION: Very common bee, especially abundant from June through October. In the early spring, individuals seen are likely queens that have overwintered—they appear worn with ragged wings and worn-down mandibles. Smaller individuals that appear around the summer solstice are usually this year’s workers. Often confused with Lasioglossum (Dialictus). In both sexes, bees are moderately metallic blue or green; not matte black. HEAD: In females, the clypeus is not metallic, so appears darker than the rest of the face and protrudes slightly. The supraclypeal area is rectangular, with the subantennal sutures longer than the epistomal suture so that the face is longer than broad. In males, the face is oval-shaped—much longer than broad, and the underside of the antennae is light yellow. THORAX: The dorsal surface of the propodeum is finely and unevenly striated. WINGS: The wings are clear with no smoky coloration. LEGS: In males, the trochanter and the femur on the forelegs are yellow. ABDOMEN: In females, apical hair bands across T3 and T4 are broad throughout, not narrowing in the middle (in older Halictus confusus specimens this may be hard to see). (male) The eyes slightly converge ventrally, and the supraclypeal area is elongated so that the whole face is longer than it is wide. The clypeus appears slightly darker than the rest of the face and body, though in males, the lower edge is yellow. Hair bands on T3 and T4 are strong, even in the middle.

Halictus confusus (female)

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HALICTUS 49

The bee body exhibits a dull metallic sheen.

The wings are relatively clear.

The propodeum has strong deep grooves running across its dorsal surface.

Segments of legs in males are by and large yellow.

Halictus confusus (male)

The light metallic sheen on the body is evident here.

Halictus confusus (female)

SIMILAR SPECIES: Other species of Halictus in the West may look similar at first, but only Halictus Apical hair bands on H. confusus do not diminish tripartitus (which overlaps with H. confusus only in the middle on T3 and T4. in prairie states) is also dull green. Halictus tripartitus is significantly more common than H. confusus in western states. Between the two, the face of H. confusus is longer in females. In males, the color of the antennae and the foretrochanters is yellower in H. confusus than in H. tripartitus. Additionally, the striations on the propodeum are finer in H. confusus.

— Halictus farinosus SIZE: Medium; 12 mm. PHENOLOGY: April through October. FLORAL HOSTS: Broad generalist. RANGE: Widespread. New Mexico north to southern Canada, west to the Pacific Ocean. NESTING: Primitively eusocial, nest in the ground. LIFE HISTORY: Very similar to H. confusus; see above. IDENTIFICATION: Large Halictus species with no metallic tints. HEAD: In females, the head is narrower than thorax. No genal tooth protrudes from the posterior portion of the head. THORAX: No metallic tint. LEGS: Hind tibial spurs with small regular teeth. ABDOMEN: In females, tergal segments have thick, uniform apical hair bands. In males, there are short, flattened hairs on the fourth sternal segment. SIMILAR SPECIES: Similar to H. rubicundus; in females, hair bands in H. rubicundus are narrow at the center. Hind tibial spur in H. rubicundus has large irregular teeth. In males of H. rubicundus there are no appressed hairs on S4, as there are in H. farinosus.

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50 HALICTIDAE Head is slightly narrower than the thorax.

No metallic tint on the integument

Halictus farinosus (female)

Halictus farinosus (female)

Thick, uniform apical hair bands on each abdominal segment

Hind tibial spurs with small regular teeth

Halictus farinosus (male)

— Halictus ligatus SIZE: Small; 7–10 mm. PHENOLOGY: March through October in northern states, yearround in Florida. FLORAL HOSTS: Polylectic. RANGE: Widespread across North America, with records as far north as southern Canada. NESTING: Ground-nesting bee, often in large colonies, in nests that have multiple entrances. LIFE HISTORY: Very similar to H. confusus; see above. IDENTIFICATION: Very common summer bee. Body is matte black, without a metallic sheen, though the surface of the thorax is polished

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Halictus  51 The wings are clear and not too dark. The tegula and legs are yellow.

The lower half of the mandible is yellow, as is the underside of the antennae. The ocelli are well below the vertex.

The thorax is matte black in this species, but up close you can see that it is polished in between the punctures.

The head of female Halictus ligatus H. ligatus is wider females have a “tooth” than it is long. on the jaw. Note also that the presence of that tooth makes the head extremely thick.

Even in the males, the head of this species is slightly wider than the thorax.

Halictus ligatus (male)

Halictus ligatus (male)

Halictus ligatus (female)

The head is wider than the thorax in females. Halictus ligatus (female)

Even from above, the thickened gena is evident.

The thorax is shiny, polished between larger pits.

The apical hair bands on T1 and T2 aren’t as thick on H. ligatus females as they are on other specimens.

between punctures, which are small and close together. HEAD: In females, the head is large, wider than thorax, and also thick, with a protuberance (tooth) occurring at the posterior ventral corner of the gena (near the back lower margin). This is stronger or weaker depending on the specimen but is always present. In instances where the lower

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52  Halictidae

part of the face isn’t visible, the thicker genal area is still evident, being much wider than the width of the compound eye. From the front, the face is wider than long, and the ocelli are well below the vertex. In males, the lower half of the clypeus is yellow, as are the mandibles, the underside of the antennae, and the tegulae. The face is relatively round, and the wings are clear (not brown or dusky). THORAX: Punctures on scutum are fine, but deep and distinct. LEGS: In males, the tibiae are reddish, with a yellow stripe, and the tarsi are yellow. ABDOMEN: In females, apical hair bands on T1 and T2 are narrow, almost inconspicuous. In males, S2 and S3 have long hairs that stand up. SIMILAR SPECIES: No western Halictus species has the toothed gena seen in females of this bee. Halictus ligatus and H. parallelus males look similar. Halictus parallelus is rare in western areas, seen mostly in eastern or plains states. The wings of H. parallelus are darker, and the thorax is not as polished as in H. ligatus. The face of male H. ligatus is much wider than long, with the ocelli set well below the vertex, compared with other western Halictus species.

— Halictus rubicundus SIZE: Medium; 10–11 mm. PHENOLOGY: March through November. FLORAL HOSTS: Polylectic. RANGE: Widespread across North America, occurring throughout Canada and into Alaska. Also found in Europe. NESTING: Ground-nesting bee, nesting in a variety of soil types but appearing to prefer loosely packed earth. LIFE HISTORY: Eusocial or solitary bee depending on the climate. In cooler climates (Alaska, northern Canada, northern Europe), the bees are solitary. In warmer climates, the bees are eusocial, with foundresses emerging earlier in the spring than solitary individuals farther north, to start their own nests. After rearing a single brood, the female (gyne) remains in the nest rearing a second brood, while the majority of her daughters commence gathering pollen for their mother’s next batch of offspring. In the fall, next year’s foundresses mate, and hibernate for the winter. IDENTIFICATION: Medium-sized matte-black summer bee; larger than most Halictus. HEAD: In males, the eyes are angled inward, nearly converging, and the clypeus sticks out noticeably from the head; the bottom half of it is bright yellow. The mandible is nearly all black at the apex. LEGS: In females, on the hind tibia, the hindmost

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Halictus rubicundus (female)

Narow hair bands that get even narrower near the center

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Halictus  53 All male Halictus have very long antennae and narrow abdomens. Its hard to believe they are related to the females! Halictus rubicundus (female)

Clypeus protrudes from head.

Antennae are completely black.

Halictus rubicundus (male)

On the hind tibia there are two spurs. The hindmost (posterior/inner) spur has large uneven teeth on it in H. rubicundus females.

Final tergal segment lacks a hair band, unlike the other segments.

of the two spurs has large irregularly shaped teeth. Female legs are light red in color. In males, the femur and the tibia are yellow to orange, though the femur has a dark spot on it. ABDOMEN: In females, the apical hair bands are narrow, especially near the center. In males, S4 has a brush of hair along the apex and the margin of S5 is concave. Also in males, the final tergal segment does not have a band of hair. SIMILAR SPECIES: The black antennae of the males, and dark black body, combined with thin (nearly absent on older specimens) apical hair bands, are distinctive features on this bee. In the Midwest it looks most similar to H. parallelus, but the redder legs and larger body size of that bee should help to distinguish between the two.

— Halictus tripartitus SIZE: Small; 5–8 mm. PHENOLOGY: March through October. FLORAL HOSTS: Polylectic. RANGE: Super-abundant widespread species found throughout the West in large numbers. Ranges as far east as Missouri, north to British Columbia, and south to Mexico. NESTING: Ground-nesting bee, appears to prefer packed earth. Nests are often connected in the ground even though they have separate nest entrances. LIFE HISTORY: Eusocial with annual colonies. Select females (gynes) are mated in the fall and overwinter in a hole in the ground. In the spring these foundresses begin new nests and forage for pollen until their first generation of sterile daughters are mature. These smaller workers forage for pollen for a second, late-summer generation, which includes males, and next year’s gynes.

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54  Halictidae

Slightly metallic olive green

On the propodeum, the dorsal surface has strong parallel lines running across it (compare to Halictus confusus, the other slightly metallic Halictus).

Halictus tripartitus (female)

Smaller Halictus species than other western ones

Halictus tripartitus (female)

Halictus tripartitus (male)

Antennae are light brown on both sides.

Clypeus is entirely dark. Foretrochanter and base of femur are brown.

IDENTIFICATION: Small, lightly metallic bee. HEAD: The subantennal suture is short, about half the length of the epistomal suture, so that the supraclypeal area is square in shape. The malar space is short, giving the head a very round appearance. In males, the antennae are brown, only slightly lighter on the bottom than the top. Also in males, the clypeus is entirely dark. THORAX: The pits on the scutum are small but distinct. The propodeum has deep, parallel striations. LEGS: In males, the trochanter and base of the femur on the foreleg are brown, while the apical two-thirds of the femur are light yellow. SIMILAR SPECIES: For most of the West, a metallic Halictus specimen is H. tripartitus. In the Midwest, H. tripartitus and H. confusus overlap; the shape of the faces of females differs, with H. confusus females, and males to a lesser degree, having longer faces. Other differences include the color of the foretrochanters and antennae in males, and the striations on the propodeum.

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Lasioglossum  55

LASIOGLOSSUM — SUBFAMILY: Halictinae — TRIBE: Halictini OVERVIEW: Petite or small, generally metallic bees. Though their small size makes them less noticeable, by midsummer these are the dominant bees in many environments. Species range from being solitary to completely eusocial. Most nest in the ground, but some nest in rotting wood. IN THE WORLD: Worldwide there are more than 600 species. In North America there are roughly 300 species, with more than 200 species in the western U.S. and Canada. CLEPTOPARASITES: Sphecodes. IDENTIFYING FEATURES: Lasioglossum are considered one of the most difficult groups to identify with confidence. Among the many hundreds of species, the distinguishing characteristics are minute and, in many cases, grade into In Lasioglossum species that have hair bands, the band is basal, at each other. Lasioglossum, in the broad sense, consists of the beginning of each tergal four subgenera that differ markedly in their appearance. segment instead of the end. Most common are Lasioglossum (Dialictus). Though not as common as L. (Dialictus), the subgenera L. (Lasioglossum), L. (Hemihalictus), and L. (Sphecodogastra) are also frequently seen. The characteristics defining these groups bleed together. With few unique characters to identify subgenera, often combinations of many characters are required together to separate them. All are united under the genus Lasioglossum by the following: First, as with many species within the family Halictidae, the wing has a distinct arcuate basal vein, often visible in photographs taken at the correct angle. There are two or three submarginal cells (usually three), and the veins separating them are often weak. Lasioglossum specimens are usually petite, small to medium-sized bees. All subgenera of Lasioglossum have basal hair bands (i.e., at the beginning of the tergal segment). These are strongest across the first two or three tergal segments. Many specimens are shiny and may (as in the case of subgenus Dialictus) or may not (most other subgenera) have a light metallic sheen to the body. A few species have red abdomens. We include representatives from the subgenera Dialictus, Hemihalictus, Lasioglossum, and Sphecodogastra, focusing on the females. Note that many Lasioglossum occur in the West that may have similar features to the bees included here. With few exceptions, Lasioglossum are challenging to identify and require multiple keys (see references) and a microscope. Moreover, many species have not been named or described. And many males are indistinguishable from each other.

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56  Halictidae

LASIOGLOSSUM (DIALICTUS) SIZE: Petite to small; 4–10 mm. PHENOLOGY: April through October, with peak abundance during July and August. FLORAL HOSTS: Polylectic. RANGE: Widespread across western North America. NESTING: Ground nester. IDENTIFICATION: Often incredibly abundant, though the small size and diminutive habit make them easy to overlook. The head and thorax are a light aquamarine, olive green, or deep gunmetal blue color. This subgenus is unique among Lasioglossum in that the integument of the thorax always has a metallic reflection. Some species have entirely red abdomens, or abdomens with one or two red tergal segments. Features used to distinguish between species include the presence, size, and distance between puncture marks on the thorax, the degree to which the scutum is polished, the texture and ridges of the propodeal rim, the density and depth of grooves underneath the head, the pattern of the hair on the anterior face of T1, and the shape of the tegula. Many western species have not been described. Males can be especially difficult.

— Lasioglossum (Dialictus) cressonii SIZE: Small; 5–7 mm. PHENOLOGY: March through November. FLORAL HOSTS: Broad generalist. RANGE: Pacific Northwest to the Northeast, absent from the deserts of the Southwest and the Great Basin. NESTING: Nests in old rotten wood. IDENTIFICATION: Green small bee, common in the summertime. HEAD: Green head in both males and females, with light gold or blue reflections. In females, the head is relatively round, not significantly longer than it is wide. Lasioglossum In males, the antennae are elongate, with each (Dialictus) cressonii (female) antennal segment more than one and a half times as long as wide. THORAX: The The head and thorax is also gold/green, with dense thorax are green with gold reflections. pits on the scutum. Below the wing, there are no pits, though the surface is heavily corrugated. The propodeum is outlined by a strong carina that is broken right at the dorsal center; thus, the propodeum looks like it is outlined by a heart. WINGS: The wings are slightly darkened. LEGS: In males, the tarsi are yellow. ABDOMEN: The abdomen is brown. In females there are dense flattened hairs on T2-T4.

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The abdomen is brown with dense flattened hairs on T2–T4.

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Lasioglossum  57

SIMILAR SPECIES: Most similar in appearance to L. albipenne and L. oceanicum. The wings of L. albipenne are lighter, and the punctation on the scutum is sparser. It appears slightly bluer. Lasioglossum oceanicum, mostly eastern, also appears more blue than green, and the propodeal carina is not interrupted in the middle.

— Lasioglossum (Dialictus) hudsoniellum SIZE: Petite to small; 4–6 mm. PHENOLOGY: May through August. FLORAL HOSTS: Generalist, though commonly found on creosote bush (Larrea tridentata) and rabbitbrush or chamisa (Ericameria). RANGE: Alberta south to Arizona, New Mexico east to Colorado, Texas; rare in northern portions of its range. NESTING: Ground nester. IDENTIFICATION: Small bee with green thorax and red abdomen. HEAD: The head is a blue to gold green. In females, the lower half of the clypeus is rusty brown. The paraocular area (next to the compound eyes, Lasioglossum (Dialictus) hudsoniellum(female) beside the clypeus) has dense white hairs. In males, the clypeus (the lower half of which is yellow) and the areas around it are covered in dense white hair. THORAX: The tegulae are pale yellow. In females, the scutum is covered in dense, very tiny pits. The sides of the thorax are heavily corrugated, but with deep punctures as well. The propodeum has no carina running around it. In males, the thorax is polished, with deep, sparse pits. ABDOMEN: In both sexes, the abdomen is rusty red. In females, T3–T4 are covered in thick, appressed white hair. The anterior surface of T1 is polished, with only a few appressed hairs. SIMILAR SPECIES: Lasioglossum hudsoniellum is by far the most common Lasioglossum (Dialictus) species with a red abdomen, but there are other “red-tailed” Lasioglossum. Lasioglossum arenisaltans shares many of the same characters but is a sand-dune specialist and not as common as L. hudsoniellum. Lasioglossum spivakae also appears similar, but it is a smaller bee, with dark bands running across the otherwise red T1– T3. Lasioglossum spivakae is most common in Nevada and Utah. It should also be noted that L. hudsoniellum is a widespread species that varies in some of its characters; specimens from the Great Plains may have a black abdomen. Those from western deserts often have paler wing venation.

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— Lasioglossum (Dialictus) imitatum SIZE: Petite to small; 3–5 mm. PHENOLOGY: Mid-May through August. FLORAL HOSTS: Broad generalist. RANGE: Southern Canada south through Arizona and Florida. Absent only from far western states (Oregon, Washington, Nevada, and California), becoming increasingly common as one moves east. NESTING: Ground nester. Eusocial species, with colonies restarted every year by inseminated females that overwinter in the nest in which they were born. Queens and workers exist, but are not as sharply defined as in honey bees and bumble bees. IDENTIFICATION: Very small Lasioglossum (Dialictus) Lasioglossum with blue thorax and imitatum (female) brown abdomen. HEAD: Head is a pale green. In females, the gena is wider than the eye, and the head is very round. The clypeus is dark on the lower half. THORAX: Scutum is covered Head and thorax with a blue-green hue, with with fine pits. The sides of widely spaced pits the thorax, below the wings, are roughened, with no distinct pits. ABDOMEN: The abdomen is brown. On T3 and T4 there are stout, widely spaced flattened hairs. SIMILAR SPECIES: Numerous unnamed western species look similar, especially in the Midwest. Comparing to reference material is likely needed to verify this species. It is similar in size to the small L. (Dialictus) microlepoides, but that species does not have flattened hairs on T3 and T4 in females.

— Lasioglossum (Dialictus) albohirtum SIZE: Small;

5–7 mm. PHENOLOGY: May through August. FLORAL HOSTS: Broad generalist. Northwest; northern California into British Columbia and east to Alberta. NESTING: Ground nester. IDENTIFICATION: Larger green-gold Lasioglossum with abundant white hair. HEAD:  Gold/green with white hair so thick it almost covers integument. In females, head round; males with slightly longer heads. Also in females, gena with long hairs that appear like a beard, lower portion of clypeus brown. THORAX: Gold/green with widely spaced deep pits. Thick white hair covers the surface. ABDOMEN: Gold/green, like the thorax, and polished. The forward face of T1 has a thick fan of appressed white hairs. All tergal segments covered in additional white hair. The dorsal surface of the RANGE: Pacific

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Lasioglossum  59

propodeum outlined with a polished, rounded rim. SIMILAR SPECIES: Lasioglossum hyalinum appears similar to L. albohirtum in that it has abundant white hair and widely spaced pits on the scutum. It is more common in the Great Basin; both males and females have bluer metallic tints on the head and thorax, and a brown abdomen. There are two undescribed species in the West that appear similar to L. albohirtum and are more widespread. In one, females have yellow on the lower portion of the clypeus instead of brown. In the other, there is less hair, and the scutum has smaller, shallower pits.

Lasioglossum (Dialictus) albohirtum (female)

— Lasioglossum (Dialictus) pruinosum SIZE: Small; 5–7 mm. PHENOLOGY: May through August. FLORAL HOSTS: Broad generalist. RANGE: Widespread in the Midwest, and the Sonoran and Chihuahuan deserts. Absent from Nevada, California, and most of Oregon and Washington. NESTING: Ground nester. IDENTIFICATION: Larger Lasioglossum. HEAD: Light blue-green head. In females, slightly longer than it is wide, with apex of clypeus dark. In males, head is especially long and covered in thick white hair, which is yellow at the apex. THORAX: The scutum has dense pits, but near the center they are widely spaced. WINGS: The veins on the wing are light colored, with the stigma appearing almost pure

Lasioglossum (Dialictus) pruinosum (female)

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60  Halictidae

white. With magnification, tiny bright white hairs can be seen. ABDOMEN: Steel blue, with abundant white hair. SIMILAR SPECIES: Lasioglossum succinipenne and L. pilosum appear similar in that the abdomen is the same color and the face is also elongated. The pterostigma is a darker brown in these two species than in L. pruinosum, and the hair is yellower, instead of bright white. The two overlap with L. pruinosum only in north-central Canada and northern Midwest states.

— Lasioglossum (Dialictus) semicaeruleum SIZE: Small; 5–8 mm. PHENOLOGY: Late May through August. FLORAL HOSTS: Broad generalist. RANGE: Widespread in the Midwest, and the Sonoran and Chihuahuan deserts but missing from the Columbia basin, the Pacific Northwest, and California. NESTING: Ground nester. IDENTIFICATION: Larger bright metallic Lasioglossum. HEAD: In females, slightly wider than it is long. In males, the antennal segments are about one and a half times as long as wide, Lasioglossum (Dialictus) and yellow on the side that faces the face. THORAX:  semicaeruleum (female) Coarse punctation on the scutum. On the sides of the thorax, below the wings, there are coarse punctures. On the propodeum, Metallic blue-green integument the portion that faces up has sinuous ridges, but there is no strong carina separating the dorsal and posterior faces. WINGS: With light pale veins. ABDOMEN: The tergal segments are blue to green. On T1 there is a strong fan of Pits widely spaced appressed hairs on the anterior On T3–T4, thick side. On T3 and T4, thick white white hairs cover much of the surface. hairs cover the surface. SIMILAR SPECIES: Similar to L. (Dialictus) albohirtum, but that species has finer shallow pits on the thorax, and on the tergal segments, and a narrower head.

— Lasioglossum (Dialictus) zephyrum SIZE: Small; 5–8 mm. PHENOLOGY: Mid-April through August. FLORAL HOSTS: Broad generalist. RANGE: Occurs throughout the upper Midwest and into Utah, Wyoming, and Idaho, then east through to the northeastern states. NESTING: Ground nester, sometimes in aggregations with other Lasioglossum (Dialictus). Eusocial species,

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Lasioglossum  61

with colonies restarted every year by inseminated females that overwinter in the nest in which they were born. Queens and workers exist but are not as sharply defined as in honey bees and bumble bees. IDENTIFICATION: Relatively large Lasioglossum (Dialictus). HEAD: Light green, with dense hair in the paraocular region. In females the head is close to round, and the gena is just wider than the eye; in males the head is slightly elongate. In males, the clypeus is brown, and yellow at the apex in some individuals. Also in males, Lasioglossum (Dialictus) antennae are bright yellow. THORAX: Scutum highly zephyrus (female) polished, with fine sparse pits. The sides of the thorax have small fine pits that can be hard to see. The dorsal to posterior surface of the propodeum (sometimes called the metapostnotum in taxonomic keys) is gently rounded, and polished. ABDOMEN: On T1, there is a fan of white hair, pressed flat against the surface. Polished, brown with a light metallic tint and fine sparse pits. Tiny pits on SIMILAR SPECIES: Similar to L. kunzei and a roughened L. semibrunneum. Neither of those species has olive-green thorax an appressed fan of hair on the anterior surface of T1, as L. zephyrum does. Also, both of those species occur farther south and west; overlap is most common in the Midwest and North.

LASIOGLOSSUM (LASIOGLOSSUM) SIZE: Small to medium; 7–12 mm. PHENOLOGY: Most common in the summer months of June through August. FLORAL HOSTS: Polylectic to oligolectic. RANGE: Widespread across western North America. NESTING: Ground nester. IDENTIFICATION: Larger, in general, than other Lasioglossum subgenera. The head and thorax are a dark matte black, and usually with relatively few pits. Lasioglossum (Lasioglossum) species have the middle (second) submarginal cell crossvein weakened. In males, the antennae, while long, are not as elongated as in other subgenera.

— Lasioglossum (Lasioglossum) anhypops SIZE: Small to medium; 7–10 mm. PHENOLOGY: May through October; most common in June and July. FLORAL HOSTS: Generalist. RANGE: Southern California north to southern British Columbia. East to Colorado and Montana, but absent from Nevada, Arizona, and New Mexico. NESTING: Ground nester, sometimes in dense aggregations.

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IDENTIFICATION: Medium-sized dark Lasioglossum. HEAD: In females, the head is slightly elongated, to rounded. The clypeus hangs down significantly below the lower margin of the compound eyes, and there is a shallow indentation that runs from the top to the bottom of the clypeus. In males, the clypeus is entirely black, and flat against the face. THORAX: Scutum densely pitted, only moderately shiny. The portion of the propodeum that faces dorsally is strongly ridged, but there are no strong carinae separating the dorsal, lateral, or posterior surfaces. ABDOMEN: In females, the anterior face of T1 has erect hairs that extend across the entire surface, not being interrupted at the center (no acarinarium—hairless area at the center and base of T1). Tergites 2 through T5 are strongly pitted, on a roughened integument. On the second tergal segment, there is a sharp notch at the sides. Many Lasioglossum participate in an interesting mutualism. This genus, and a few others, especially in Halictidae, have a hairless area at the base of the first tergal segment that is for holding developing mites. It is often hairless, and slightly indented. The young mites attach while the bee is developing in her nest. When she begins her own nest, they transfer to the provisions in this new nest, where they complete their development while eating fungi, pollen, and other materials, Lasioglossum anhypops presumably keeping some pathogens out (female) of the bee’s nest.

On T1, there are erect hairs.

Notice the very distinct basal hair bands.

Strong ridges run along the top of the propodeum.

Lasioglossum anhypops (male)

Lasioglossum anhypops (female) Clypeus hangs down well below the lower margin of the compound eyes.

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Lasioglossum  63

SIMILAR SPECIES: Lasioglossum trizonatum looks similar, and even has a strong notch on the lateral edges of T2, but it has a bare area at the center of the anterior face of T1, which is not the case for L. anhypops. Lasioglossum coriaceum also has a similar notch on T2, but that species is found in the East, and has an acarinarium on T1.

— Lasioglossum (Lasioglossum) sisymbrii SIZE: Small

to medium; 7–10 mm. through September. FLORAL HOSTS: Generalist. RANGE: Widespread throughout the western U.S., as far east as Nebraska, Oklahoma, and eastern Texas. South through Mexico and north into southern Canada. NESTING: Ground nester, often in aggregations. IDENTIFICATION: Abundant and common bee species found throughout the West. HEAD: Dark in both sexes. Clypeus projects down below the level of the compound eyes notably. In females, the first flagellar segment is about as long as the second. Also in females, the head is about as wide as long, lightly polished. In males, the head is longer than it is wide. THORAX: Black. Tegulae pale yellow, and see-through. Scutum shiny with uniform, dense pits, separated by slightly less than their width. ABDOMEN: There is a strong basal hair band that runs across T1 in both sexes. This segment is shiny, with fine shallow pits, and some elongate hairs scattered over the surface facing the thorax. PHENOLOGY: March

There is an unmistakable patch of hair across the base of T1 in L. sisymbrii.

Lasioglossum sisymbrii (female)

Lasioglossum sisymbrii (male)

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64  Halictidae

SIMILAR SPECIES: The complete basal hair band running across T1 can distinguish this species from all other Lasioglossum species in North America. If the hair band is rubbed off from age, the pale, see-through tegulae are also unique.

LASIOGLOSSUM (SPHECODOGASTRA) SIZE: Small; 6–9 mm. PHENOLOGY: Peak abundance is July and August. FLORAL HOSTS: Several species are specialists on Onagraceae, and many species are generalists. RANGE: Widespread across North America; not uncommon at higher latitudes and elevations. NESTING: Ground nester. IDENTIFICATION: Rarer than other Lasioglossum subgenera, and some species are confined to flying during the evening or dawn. The head and thorax are black, with no metallic reflections. In some females, the ocelli are incredibly large. The second submarginal crossvein is weak. The inner midtibial spur has variable teeth, set in a row like a rake. The females have a carina that runs around the propodeum, separating the sides from the posterior face. And there are fine pits on the thorax and abdomen. A few species have no carina around the propodeum, but in these species, the scopa on the femur is sparse, with stout widely spaced hairs.

— Lasioglossum (Shecodogastra) texanum SIZE: Small to medium; 7–11 mm. PHENOLOGY: April through December, but most common May through July. FLORAL HOSTS: Specialist on Oenothera. RANGE: Intermountain west and Midwest, as far as Michigan. South to Arizona and New Mexico. NESTING: Nests in sandy areas. IDENTIFICATION: A bee that flies at dusk, or dawn, and through the night when the moon is up (though, apparently, not as much during a full moon). HEAD: Extraordinarily large ocelli that look like droplets of water set on top of the head. In females, mandibles are not overly elongated. Head is round, to very slightly wider than long. Gena is narrower than the width of the compound eye. Antennae are orange brown. THORAX: Scutum dull, pits sparse and deep. Tegulae are light brown. No carina around the propodeum.

Lasioglossum texanum (female) The ocelli are huge!

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Lasioglossum  65 LEGS: In females, inner hind tibial spur has three or four short teeth. ABDOMEN: Bright red/orange, fading to light brown for T4–T5 (and maybe T3). The first tergal segment is shiny, and highly polished, with very fine sparse pits. SIMILAR SPECIES: Similar in appearance to L. noctivaga, which also flies at dusk, has a red abdomen, and has enlarged ocelli. Lasioglossum (Sphecodogastra) noctivaga has very long mandibles (in females) that cross at the front of the face. Males of the two species are indistinguishable without seeing the genitalia.

— Lasioglossum (Hemihalictus) SIZE: Petite to small; 4–8 mm. PHENOLOGY: April through October, with peak abundance during July and August. FLORAL HOSTS: Polylectic. RANGE: Widespread across western North America. NESTING: Ground nester. IDENTIFICATION: May be difficult to distinguish from other subgenera of Lasioglossum, especially Lasioglossum (Lasioglossum). In the U.S. and Canada, the head and thorax are black with no metallic reflections. The head may be wider than long or vice versa, but, in females, the clypeus usually hangs below the lower margins of the compound eyes significantly. The second submarginal crossvein is weakly defined, or even absent (compare with Lasioglossum [Lasioglossum] and [Sphecodogastra], where the second submarginal crossvein is very strong). Also, the angles on the propodeum are usually weakly defined, so that the sides, dorsal face, and the posterior face are not clearly separated. In a few species, there is a strong carina around the posterior face of the propodeum, but in those cases the thorax tends to be heavily pitted.

— Lasioglossum (Hemihalictus) pulveris SIZE: Small; 5–7 mm. PHENOLOGY: June through September. FLORAL HOSTS: Generalist. RANGE: Rocky Mountains and Sangre de Cristo Mountains west to California; absent from the Great Basin, and the Pacific Northwest. NESTING: Presumably ground nesting. IDENTIFICATION: Dark slender bee with relatively narrow abdomen. HEAD:  In females, matte black with fine sparse dull-white hairs. Face is longer than it is wide. Clypeus extends below lower margin of face; shiny, but with distinct sparse punctures, especially on lower part. THORAX:  Abdomen polished; each segment In females, scutum is fades to brown toward the apex.

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Lasioglossum pulveris (female)

Matte-black head and thorax

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roughened, with small moderately spaced pits. Scutellum is also sparsely punctate, over a more polished integument. Tegula is partially translucent. The dorsal surface of the propodeum has a shining rim running around it. ABDOMEN: Polished dark integument, with lighter brown coloring at the apex of each segment. Sparse but consistent pits occur on the surface. No clear hair bands on any tergite. SIMILAR SPECIES: Similar bees include Lasioglossum synthyridis. That species has dark tegulae, and a wider abdomen. Lasioglossum foxii has a shorter clypeus.

SPHECODES — SUBFAMILY: Halictinae — TRIBE: Halictini OVERVIEW: Sphecodes are small to medium-sized cleptoparasitic bees. Females are usually black on the thorax, with a blood-red abdomen (sometimes with black stripes), while males are either red and black or all black. Sphecodes do not collect pollen. They parasitize ground-nesting bees, usually in the family Halictidae. IN THE WORLD: Worldwide there are about 350 species, occurring on all continents, though rare in Australia. In the Americas, this genus ranges from southern Alaska south through Argentina. In the U.S. and Canada there are more than 70 species, more than half of them occurring in the West. CLEPTOPARASITES: Sphecodes are cleptoparasites; typical hosts include Halictus, Lasioglossum, Andrena, and Colletes (all ground nesters). IDENTIFYING FEATURES: Small to medium-sized bees; easy to overlook at first glance but warrant a double-take for the bright red abdomen. HEAD: Generally oval-shaped, wider than long with a short and broad clypeus. Antennae are entirely black. THORAX: Sculpturing is thick, with large indentations, and the integument in between is not polished. WINGS: The arcuate basal vein typical of many Halictidae is evident. LEGS: Females often have spines on their hind legs. ABDOMEN: In females, the fifth tergal segment usually has a white tuft of hair. The abdomen of females is almost always red; males are also often red, though they may have more extensive black markings. SIMILAR GENERA: Several bee genera have red-and-black abdomens like Sphecodes, and they may at first glance appear similar. A few Lasioglossum have a red abdomen, but the color on those bees is closer to orange, and the thorax is coppery. Ashmeadiella individuals with red abdomens may resemble female Sphecodes. Scopal hairs on the abdomen of female Ashmeadiella should distinguish them from Sphecodes; in addition, Ashmeadiella have two submarginal cells, while Sphecodes nearly always have three. Some Andrena also have red abdomens. The presence of pollen-collecting hairs on female Andrena should distinguish the two; Sphecodes also have much narrower, parallel-sided abdomens compared with Andrena, and Andrena lack an arcuate basal vein. Finally, Sphecodes males, with their red-and-black abdomens, may look similar to Halictus species—the unpolished integument, the wider face, and the shorter antennae should distinguish the two.

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Sphecodes  67

Sphecodes are difficult to identify to species. We have chosen just one of the numerous species to include here. For other species, positive identification is best done with a microscope and taxonomic keys (see references); no key exists that includes all western specimens.

— Sphecodes arvensiformis SIZE: Medium; 10 mm. PHENOLOGY: May through August. FLORAL HOSTS: Cleptoparasite; no floral preferences. RANGE: Primarily mountainous areas in the western U.S.; largely absent from the Great Basin in Nevada. NESTING: Cleptoparasite of Halictus. IDENTIFICATION: Black bee with bright red abdomen. HEAD: Wider than long, with dark eyes. In females, mandibles black, with a dark red spot just before the apex. THORAX: Dark integument, polished. Pits on scutum are widely spaced; less evenly spaced on the scutellum where integument is distinctly roughened. WINGS: Dark. Long, extending half the length of the abdomen. ABDOMEN: Highly polished, and almost entirely lacking pits. In females, the abdomen is completely red. SIMILAR SPECIES: Sphecodes are notoriously difficult to tell apart, but the red spot on the mandible is distinctive and can help identify this species.

Wings dark

Sphecodes arvensiformis (male)

Sphecodes arvensiformis (female) Pits grow sparse toward the back of the scutum.

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Bright red highly polished abdomen with almost no pits

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68  Halictidae

DIEUNOMIA — SUBFAMILY: Nomiinae OVERVIEW: Large dark bees; easy to spot when they occur, but neither widespread nor abundant. Most are seen in the late summer and fall when Asteraceae bloom; they are all specialists on this plant family. Often nest in large aggregations, with nests deep enough that they can survive in plowed fields. Thus, many species in this genus are common in agricultural areas. IN THE WORLD: Nine species total. All are restricted to the Americas. Most abundant in Central and South America. Eight occur north of the Mexican border; all can be found in the western U.S., and a few occur as far north as eastern Canada. CLEPTOPARASITES: Triepeolus species, especially T. distinctus. IDENTIFYING FEATURES: Sizable bees, usually with dark integument and auburn hair. HEAD: In males, the last segment of the antenna is flattened and broad. WINGS: Basal vein is not arcuate, as it is in many other Halictidae. LEGS: In females, scopal hairs occur thickly on the hind legs but also extend onto the underside of the abdomen (S2–S5), almost wrapping onto the terga. In males there are often protrusions and extra structures on the mid and hind legs that can be distinctive. ABDOMEN: In both sexes, when viewed from above, there is an indentation in the forward (anterior) face of the first tergal segment, causing it to appear like a V. SIMILAR GENERA: Andrena species can look like Dieunomia, as both share a similar body shape (andreniform). The indentation on T1 is a key factor in telling the two apart, as is the facial fovea in female Andrena. Larger Apidae (e.g., Xylocopa) may also be confused with Dieunomia. Look for the distinct scopal hairs in females, and the flattened antennae in males, of Dieunomia.

— Dieunomia heteropoda SIZE: Large;

18 mm. through October. FLORAL HOSTS: Specialist on plants in the Asteraceae, especially sunflowers (Helianthus). RANGE: Maine and Ontario south through Florida, west to Utah. NESTING: Groundnesting bee. Appear to be solitary, but multiple females have been observed to use the same nest entrance in some cases. Often nest in aggregations of a hundred to several hundred. Nests can be recognized by mound of dirt, often sandy areas, with nest entrance at the base of the mound. IDENTIFICATION: Large dark bee with exceptionally long wings that are often held up and out from body in a distinctive fashion. HEAD: The gena is thick, at least as wide as the width of the compound eye. WINGS: Wings are brownish, with the tips especially PHENOLOGY: July

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Dieunomia  69 Head thickened behind compound eye

Dieunomia heteropoda (female)

Wings dark, or at least with dark edges

Lower margin of first and third submarginal cell about the same length Notch in forward face of T1

Dieunomia are specialists on sunflowers and time their emergence with peak sunflower bloom across their range. They often bob their abdomen up and down as they forage for pollen. Scopal hairs both on the legs and on the underside of the abdomen

Dieunomia heteropoda (female)

Males have interesting protrusions on their legs that they apparently use to grip the female while mating. Dieunomia heteropoda (male)

Dieunomia engage in elaborate mating rituals that involve waggling antennae and vibrating wing muscles.

Antennae are flattened at the tips in males. Notch in T1 (also abdomen is often reddish brown)

dark. LEGS: In males, the hind femur is swollen, and the hind tibia is enlarged and triangular in shape. The basitari are also greatly elongated, with a fringe Dieunomia heteropoda (male) of hair on the inner surface. THORAX: Covered with many dense pits. SIMILAR SPECIES: Dieunomia triangulifera is lightly smaller, and without smoky or dark wings (though may be clouded at the very tips). Dieunomia nevadensis is much smaller (about half the size), with a thinner face and clear wings.

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— Dieunomia nevadensis SIZE: Small

to medium; 8–12 mm. through October. FLORAL HOSTS: Specialist on Asteraceae. RANGE: Oregon east across the Great Plains. Occasional in states further east. Wyoming south to Mexico. NESTING: Ground nester, often with several bees nesting in close proximity to each other. IDENTIFICATION: Small species (males more petite than females), dark with long smoky wings. HEAD: Round, as wide as it is long in both males and females. Integument dark, but covered with dense short, Dieunomia slightly yellowish hair. In nevadensis (male) males, antennae are long, Abdominal segments constrict at base making extending back as far as the abdomen appear wavy. scutellum. THORAX: Tegulae pale yellow. In males, hair is thick. WINGS: Clear to orange, exceedingly long, with a dark spot at the apex. LEGS: Red to Wings darkened orange. In males, the hind basitarsus toward the tips is broad and the femur appears V-shaped notch at the base of T1 swollen. On the apical half of the tibia there is a broad Abdomen may be red/orange or black, indentation. ABDOMEN: In depending on the females, tergal segments subspecies. lined with thin hair bands. In males, T1 and T2 have a deep indentation that runs across them. Integument Round may be dark, or may be red, head depending on the subspecies. SIMILAR SPECIES: There are five subspecies of Dieunomia nevadensis: D. n. Dieunomia nevadensis (female) arizonensis, D. n. angelesia, D. n. nevadensis, D. n. stellata, and D. n. bakeri. Dieunomia nevadensis arizonensis usually has a red abdomen. Dieunomia nevadensis nevadensis has a yellowish-red abdomen, while D. n. bakeri is all black, and is the largest of the species. PHENOLOGY: August

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Nomia  71

NOMIA — SUBFAMILY: Nomiinae OVERVIEW: Medium to large dark bees with light pearlescent bands on their abdomen. A few species specialize, but the majority are generalists. Often nest in large aggregations with more than 1,000 nests in a few square meters. Sometimes multiple females will share one entrance, though inside the nest each female digs and provisions her own nest cells. Includes Nomia melanderi, the alkali bee, widely used in the West for pollinating alfalfa. IN THE WORLD: More than 130 species are found worldwide; nine of these can be found in North America (north of Mexico); eight occur in western North America. CLEPTOPARASITES: Nomia is seldom parasitized by other bees; a few scattered reports of Nomada entering Nomia nests are all that have been observed. IDENTIFYING FEATURES: Medium-sized bees with pearlescent hair bands on abdomen; stunning bee, but seldom seen. HEAD: Face is round, about as wide as long but may be slightly longer than wide; always tapering slightly as inner eye margins converge. Malar space is barely evident. Face may be covered with dense white hairs. THORAX: Deep black, with widely spaced, distinctive pits. WINGS: Basal vein is not as distinctly arcuate as in many other Halictidae. LEGS: In females, scopal hairs are thick and stout on the femur and tibia. ABDOMEN: Wide, unpitted, shiny ivory-colored bands take up the apical quarter to third portion of each tergal segment. SIMILAR GENERA: This genus is alone in having ivory bands on the tergal segments. Should these not be visible, the converging compound eye margins are somewhat similar to the eye margins of Colletes. Wing venation should be distinguishing (see Colletes), in addition to the slenderer body of Colletes.

— Nomia melanderi SIZE: Medium; 12–13 mm. PHENOLOGY: April through October. FLORAL HOSTS: Generalist, but with some preference for Fabaceae. An excellent pollinator of alfalfa (Medicago), because it doesn’t appear to mind the “tripping mechanism” of the anthers, triggered when a bee roots for nectar. RANGE: Western species, as far east as central Colorado, but rare in southwestern states. NESTING: Ground, sometimes in large aggregations (the world’s largest recorded aggregation of solitary bees is N. melanderi). Appears to prefer salty or alkaline soils. IDENTIFICATION: Large bee with striking iridescent or pearly bands running across the abdomen. HEAD: In females, antennae slightly elongated, black. In males, antennae are brown, elongated, and taper to a fine point. THORAX: The scutellum is smooth and

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72  Halictidae Nomia melanderi (female)

Iridescent pearly bands at the apex of each abdominal segment

T1 has a thin or incomplete light band, at least on the sides.

Antenna clearly lighter on the underside

Nomia melanderi (male)

lacking in much punctation. In females, anterior half covered with pale gray hairs, intermixed with some black hairs. WINGS: Clear, with some darkening near apex. LEGS: In males, tarsi are light colored, especially apically. Also Hind femur is swollen and the in males, the hind femur is hind basitarsus Tarsi are light is flattened. colored. swollen, and the hind basitarsus is flattened into an elongated misshapen triangle. ABDOMEN: In both sexes, T2–T4 have complete bands of opalescent green running across them, while T1 may have a complete thin band, or it may be absent medially, but with some light markings on the sides. Pits on T3 often smaller, and less dense than on T2. SIMILAR SPECIES: There are eight species of Nomia in the western U.S. and Canada. Nomia melanderi and only a handful of others exhibit iridescent bands on the apex of T1. In female N. foxii and N. nortoni, the band is interrupted medially, so that it shows only at the edges. Nomia howardi and N. melanderi are very similar looking. Nomia melanderi is more common, and more widespread, while N. howardi is a southern species, most common along the border with Mexico (but occasionally occurring farther north). The band of iridescence that runs across T1 in N. howardi tends to be thicker, occupying more of the tergal segment than in N. melanderi, but this trait is variable. Also, the outer hind tibial spur is more bent (often to nearly 90° in N. melanderi). In males, the band on T1 is often absent in males of N. melanderi, but always present in N. howardi.

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Nomia  73

— Nomia tetrazonata SIZE: Small

to medium; 8–12 mm. through October. FLORAL HOSTS: Generalist, seen on many plants throughout the Southwest, but many records from Fabaceae and Larrea tridentata. RANGE: Northeastern Texas west to southern California. Absent in northwestern states but common in the Southwest (and through Central America). NESTING: Ground nester, occasionally in small aggregations. IDENTIFICATION: Modest dark bee Nomia tetrazonata (female) with iridescent stripes on the abdomen. HEAD: Round, with slightly converging eyes. In males, face is densely covered in white hair. THORAX: Pits on scutum are evenly distributed and of even size on a polished integument. WINGS: Shorter than other Nomia species. LEGS: The hind femur is short, and the tibia is flattened into a misshapen triangle. ABDOMEN: Iridescent band absent from apical rim of T1, but present Iridescent bands on T2–T4. In females, the pits on T2 absent on T1 but present on T2–T4 are about the same size as those on T3. SIMILAR SPECIES: Most similar Antennae uniformly dark to Nomia universitatis. Nomia universitatis is a midwestern species, occurring occasionally in New Mexico and southern California, while N. tetrazonata is more common in the Southwest. Between the two, the N. tetrazonata has slightly shorter wingſ, and denſer Nomia tetrazonata (male) Hind tarsi dark pits on T4. There are two subspecies of N. tetrazonata. PHENOLOGY: March

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74  Halictidae

CONANTHALICTUS — SUBFAMILY: Rophitinae OVERVIEW: Conanthalictus are small, rare bees that are found only in North America’s hot deserts. Little is known about most species in this genus, though all are thought to be floral specialists, mostly on Boraginaceae. Those species that have been studied nest in the ground. IN THE WORLD: Thirteen species, mostly found in the Mojave, Sonoran, and Chihuahuan deserts. CLEPTOPARASITES: Townsendiella. IDENTIFYING FEATURES: Dark and petite, easy-to-miss bees; up close a light green sheen is evident. HEAD: There are two subgenera of Conanthalictus. In one group (Conanthalictus), the head is elongated, with short antennae placed low on the face. In the other group, the head is wider than long (Phaceliapis). In both subgenera, the clypeus is shortened significantly, and much wider than long, with the antennae arising just above the clypeal margin. THORAX: Lightly roughened, metallic. Propodeum is elongated, so that when measured from above it is as long as, or longer than, the scutellum. WINGS: Clear, almost iridescent. Unlike most Rophitinae, there are three submarginal cells. The first recurrent vein meets the second submarginal cell just beyond its center. LEGS: Scopae on hind femurs and trochanters very short and sparse. Scopae on tibiae only slightly longer. ABDOMEN: Long and narrow, slightly flattened. May be red in some species. In males, there is a dense fringe of hair that can hide T7. SIMILAR GENERA: Conanthalictus look very similar to Lasioglossum, because of the metallic undertones on their integument. The shortened face, and small clypeus with low antennal sockets should distinguish. They also appear similar to other rophitines (Dufourea, Protodufourea, etc.). In North America, very few rophitines have three submarginal cells. They can be distinguished from those that do by the simple tibial spurs, small size, metallic color, and elongated propodeum.

— Conanthalictus bakeri SIZE: Petite to small; 4–5 mm. PHENOLOGY: March through June. FLORAL HOSTS: Scorpion weed (Phacelia), though occasionally collected on other plants. RANGE: Southern California and southern Nevada east through New Mexico and West Texas. NESTING: Presumed to nest in the ground. IDENTIFICATION: Petite bee, generally similar in appearance to Lasioglossum, with dark metallic green body. HEAD: Round face, about as broad as long, with short mandibles. Mandibles have small inner tooth. In males, the antennae are shortened and appear thick. THORAX: In both males and females, relatively dull, with thin fine sculpturing under pits on scutum. ABDOMEN: Green in both males and females.

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Dufourea  75

Short, thick antennae 3 submarginal cells (as in all Conanthalictus, but not other Rophitini)

Conanthalictus bakeri (male)

Round face Conanthalictus bakeri (female)

Metallic blue-green integument

SIMILAR SPECIES: Conanthalictus wilmattae appears similar in that it also has a green abdomen in both males and females (other species of Conanthalictus in North America have black or red abdomens). The two can be distinguished by the thicker patches of white hair near the antennae on the face in C. wilmattae, which are very sparse in C. bakeri.

DUFOUREA — SUBFAMILY: Rophitinae OVERVIEW: Small, usually dark bee, seldom seen, but may be locally abundant. Dufourea are all specialists, often on just one genus of flowering plant. Groundnesting species. IN THE WORLD: 170 species total. Found throughout the Northern Hemisphere, but most common in the western U.S. Around 70 species in North America, with nearly all of them occurring in the western states. CLEPTOPARASITES: Neopasites. IDENTIFYING FEATURES: Andreniform in shape, generally small to medium in size. HEAD: Antennae are very low on the face accompanied by a very short clypeus. Only one subantennal suture. The clypeus juts out from the face when viewed from the side. WINGS: There are two submarginal cells; nearly all other Halictidae covered in this book have three. The basal vein is not arcuate, as it is in many other Halictidae. LEGS: Males often have modifications and projections on the hind legs. THORAX: May be black, or dull dark metallic green. Occasionally red. Usually without hair bands; if present, not very strong.

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76  Halictidae

SIMILAR GENERA: Across all Dufourea, there is some resemblance to smaller Andrena, but the shape of the face, with the low antennae and single antennal suture, should be distinctive. Small Halictus may also resemble Dufourea. Two versus three submarginal cells, and the low antennae should distinguish the two.

— Dufourea maura SIZE: Small; 10 mm. PHENOLOGY: June through August. FLORAL HOSTS: Specialist on Campanula. RANGE: From coast to coast in southern Canada and northern states. Extending south along the Rocky Mountains and nearby areas. NESTING: Ground-nesting bee. IDENTIFICATION: Small bee with black integument and dark hair. HEAD: Head is distinctly wider than it is long; just wider than thorax. Clypeus protrudes from lower half of face notably. THORAX: Hair on Head wider than Hair 0n the thorax thorax dark thorax is dark in both males and females. In females, propodeal triangle is polished, with long deep corrugations running across it. The scutellum is largely unpitted at its center. LEGS: In females, Dufourea maura scopae are dark, either Dark scopal hairs (female) brown or black. In males, hind femur is longer than its widest point, and possesses a distinct spine at the base. The hind tibia is expanded, looking flattened Dark hairs on with a wide, smooth curve the thorax on the side facing the body. ABDOMEN: Smooth and polished, with hair at the apex of the later segments.

SIMILAR SPECIES:

Dufourea dilatipes is similar in having a head that is wider than it is long (many Dufourea have very long heads). The propodeal triangle of D. dilatipes is dull, without strong corrugations across the top. Also, the scutellum of D. dilatipes is densely punctate.

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Dufourea maura (male)

Hind femur with distinct spine at the base

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DUFOUREA 77

— Dufourea mulleri SIZE: Small; 7–8 mm. PHENOLOGY: April and May. FLORAL HOSTS: Phacelia specialist. RANGE: Most common in the southwestern U.S., from southern California east to New Mexico, with occasional records farther north. NESTING: Ground-nesting bee in gravelly or sandy soils. IDENTIFICATION: Small dark bee. HEAD: Dark with a metallic blue tint, slightly wider than it is long. Mandibles short and stout. Antennae appear short and slightly clipped at the tip. THORAX: Hair on thorax is light in both males and females. WINGS: Lightly smoky. ABDOMEN: In females, T2–T4 have thick bands of white hair running across the abdomen; these are less obvious in older specimens. SIMILAR SPECIES: Appears similar to D. marginata, but the head is blue-tinted, and the abdomen has stronger hair bands and darker wings. Females of D. mulleri are indistinguishable from those of D. trochantera. In males, the strongly produced ridge Light hairs on head and thorax on the hind trochanter of D. trochantera is distinctive. Head with a bluish tint Dufourea trochantera is more common in the Northwest, while D. mulleri is more abundant further south.

Dufourea mulleri (male)

Hair on thorax and head light

Dufourea mulleri (female)

Head with a bluish tint

Light scopal hairs

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78  Halictidae

— Dufourea trochantera SIZE: Small; 8 mm. PHENOLOGY: May through July, depending on elevation. FLORAL HOSTS: Phacelia specialist. RANGE: Mostly northwestern states and southwestern Canada, but occurs as far east as Wyoming, and as far south as high-elevation sites in southern California. NESTING: Ground nester.

Light hair on head and thorax

Dufourea trochantera (female)

Light scopal hairs

Light hairs on head and thorax

Hind trochanter has a sharp narrow ridge on the underside.

Dufourea trochantera (male)

IDENTIFICATION: Small dark bee. HEAD: Dark with a metallic blue tint, slightly wider than it is long with eyes converging near clypeus. Mandibles short and stout. Antennae appear short and slightly clipped at the tip. THORAX: Scutum with pits unevenly and widely spaced throughout. WINGS: Lightly smoky. LEGS: In females, scopae are light. In males, hind trochanter has a sharp and narrow ridge on the underside, so that the segment is twice as wide as it is long. ABDOMEN: In females, T2–T4 have thick bands of white hair running across the abdomen. Tergal segments are deeply and densely pitted. SIMILAR SPECIES: See Dufourea mulleri.

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Micralictoides  79

MICRALICTOIDES — SUBFAMILY: Rophitinae OVERVIEW: Very small matte-black bees. Some species have a red abdomen that darkens toward the tip. It appears that all species are specialists, though the plant family varies across species. Nesting preferences are unknown, but it is presumed to be a ground nester. IN THE WORLD: Eight species are found in the world, and all occur in the southwestern U.S. and northern Mexico. CLEPTOPARASITES: Unknown. IDENTIFICATION: Small (4–6 mm), easy-to-overlook bee. HEAD: Antennae are low on face, only just above clypeus. In females, though hard to see, the maxillary palpi are nearly as long as the flagellum. THORAX: Nonmetallic. On the side of the thorax, there is a depression that runs from the mesepisternal suture to the end of the mesepisternum. WINGS: Two submarginal cells; the first is twice as long as it is wide. LEGS: Tibial spurs are translucent yellow, with a few widely spaced needlelike teeth. Tarsal segments are lighter colored than the femurs. ABDOMEN: In males, abdomen is as broad as thorax (compare with male Lasioglossum). SIMILAR GENERA: Overall, appears similar to small Lasioglossum (Dialictus), but the lower placement of the antennae on the face should serve to distinguish the two, as well as the difference in number of submarginal cells. Among Rophitinae in North America, the distinctly lighter hind basitarsus as compared with the femur is distinguishing. It may also superficially resemble Dufourea, but the clypeus does not protrude from the face in this bee, as it does in Dufourea.

— Micralictoides ruficaudus SIZE: Petite; 4–5 mm. PHENOLOGY: March through May. FLORAL HOSTS: California poppy (Eschscholzia sp.) specialist. RANGE: California, in the foothills and mountains of central and southern California. NESTING: Unknown. IDENTIFICATION: Small bee with red abdomen, usually seen burrowed into Eschscholzia flowers. HEAD: Dark head. In males, antennae are short. Punctation is dense. In females, the face is shinier, with punctation slightly less close together. ABDOMEN: Punctation on the abdomen in males and females is coarse. In females, T1–T3 are orange/red, but there is a dark spot on the sides of T2. In males, the abdomen is orange or red, especially on T1–T3. SIMILAR SPECIES: The red-orange abdomen of M. ruficaudus is rare in Micralictoides. Only females of some M. linsleyi also have the orange tergal segments, but the frons is very roughened in these individuals, while in M. ruficaudus it is shinier. In addition, in males the antennae are very short.

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80  Halictidae Two submarginal cells; the first is longer than the second. Micralictoides ruficaudus (female) Head dark with dense punctation

Micralictoides ruficaudus (male)

T1–T3 orange/red with a dark spot on the side of T2 Abdomen red, especially T1–T3

Coarse punctation on abdomen

XERALICTUS — SUBFAMILY: Rophitinae OVERVIEW: This is a genus of bees with only two species. The bees are larger than other rophitines, so they may be more noticeable, but their range is small, so they are not as commonly seen. Both species are specialists on blazing star (Mentzelia) and may be the primary pollinator of many of these species. Nesting specifics have not been well studied, but one record exists of Xeralictus nesting in a shallow depression on a talus slope, and females are often observed flying around on steep rocky slopes exploring cracks, holes, and other “caves.” IN THE WORLD: There are only two species of Xeralictus in the world, and both occur in hot deserts of the southwestern U.S. and northern Mexico. CLEPTOPARASITES: None documented. IDENTIFICATION: Larger rophitine species usually seen in the afternoons on blazing star (Mentzelia) flowers in desert regions. HEAD: In males, the mandible is wide, with a broad angle on the upper side. WINGS: There are three submarginal cells. LEGS: In both males and females, the inner and outer hind tibial spurs are coarsely serrated. ABDOMEN: In males, T7 is broad, with no pygidial plate, and usually covered in thick hair. SIMILAR GENERA: Xeralictus stands out from other Rophitinae because of the three submarginal cells, the larger size, and the serrated hind tibial spurs. It does appear similar to Hesperapis (Xeralictoides), but that genus has only two submarginal cells.

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Xeralictus  81

— Xeralictus bicuspidariae SIZE: Medium; 10 mm. PHENOLOGY: April through May. FLORAL HOSTS: Specialist on blazing star (Mentzelia) species. RANGE: Mojave Desert; southern California east through southern Arizona and north through Clark County, Nevada. NESTING: Ground nester. IDENTIFICATION: Smaller species. HEAD: In both males and females, the head is slightly longer than it is wide. THORAX: Scutum shiny with fine punctures that become sparse near the center. LEGS: In males, hind tibial spur with two or three fine, strongly curved teeth. ABDOMEN: In females, the abdomen is primarily rusty red, though T2 often has a dark brown spot on each side. In males, S4 is not strongly angled on the sides. SIMILAR SPECIES: There is only one other species of Xeralictus: X. timberlakei, which is bigger. Females of that species have a black abdomen and a head that is slightly longer than it is wide. In males, Xeralictus bicuspidariae (male) S4 is strongly angled and looks distinctly different from that of X. bicuspidariae. In both male and female X. timberlakei, there are five or six teeth on hind tibial spurs, instead of just two or three.

Scutum shiny with fine punctures, sparse near center

Abdomen bright red often with a dark spot on the sides of T2

Head slightly longer than wide Three submarginal cells

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Xeralictus bicuspidariae (female)

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82  Colletidae

COLLETIDAE

Colletidae are widely distributed around the world, consisting of diverse genera that range in appearance from minuscule, hairless black bees to large, fast-flying, fuzzy bees. Despite the worldwide variety, in North America just two genera are common: Colletes and Hylaeus, and a few genera found only in the southwest. All are solitary, though many species of Colletes nest in aggregations of several hundred. The family includes both ground and cavity nesters, and nests are lined with a cellophanelike secretion. Within Colletidae are bees that are narrow specialists, as well as bees that broadly generalize. There are no cleptoparasitic bees in the Colletidae. IDENTIFICATION: Identifying a bee as a Colletidae is often harder than identifying the bee at the genus level, as the genus characters are easier to see without a microscope. Memorizing the features that distinguish, especially, Colletes and Hylaeus will be most useful. Colletidae are united in that they all have a short glossa, which is generally thick (wider than long). At the end it is either abruptly truncated, or more often bilobed (forked). Note that unlike Andrenidae, Colletidae have one subantennal   suture. Little else unites this family, Bees in Colletidae have unique morphologically. Behaviorally, all North “tongues,” with a short glossa and American Colletidae line their nests with a often a bilobed, or forked, tip. cellophanelike material that is unique to this family, though some genera nest in the ground while others nest in hollow twigs. TAXONOMY: There are about 2,500 species of Colletidae, found on every continent (reaching peak diversity in South America and Australia), in 54 genera. In the U.S. there are five genera split into three subfamilies; in the western U.S. and Canada can be found three of those genera, two of which are covered here.

—  SUBFAMILY COLLETINAE In North America, there is just one genus, described below. Colletes. A medium-sized bee, very common in the spring and fall (many specialize on early and late blooming flowers). Females resemble Andrena in body shape. On the wing, the second recurrent vein is strongly curved. The inner margins of the compound eyes converge toward the lower portions of the face.

—  SUBFAMILY HYLAEINAE There is just one genus in this subfamily in North America. Hylaeus. Minuscule, black, hairless bee. Most species have yellow markings on the face. On the wing, there are two submarginal cells. There are no scopal hairs in females, as they ingest pollen and nectar and regurgitate both in nest cells.

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Caupolicana  83

—  SUBFAMILY DIPHAGLOSSINAE: There are three relatively rare genera in this subfamily of large fuzzy bees in North America. All have pointed, bifid glossa. One of these genera is common in the Southwest (Caupolicana); the other two are rare and are not featured here. — C AUPOLICANINI Caupolicana, Ptiloglossa, Zikanapis Within the Colletidae genera found in North America there are more than 150 species.

CAUPOLICANA — SUBFAMILY: Diphaglossinae OVERVIEW: Large fast-flying bees, usually seen early in the morning, and very rarely. Ground-nesting bees, many with a preference for sandier soils; mothers may regurgitate nectar to mix with the soil substrate in nest creation. Some species may fly in the dark, as many of the specimens that have been collected are covered in moth scales, suggesting they were collected in light-traps used normally to attract night-flying moths; additionally, they have been heard flying when it was too dark for humans to see. Among Caupolicana, some species are specialists, but others generalize. IN THE WORLD: Found in the Western Hemisphere. There are 37 species in North and South America. In the U.S. there are around four species, two in the East and two in the West. CLEPTOPARASITES: Triepeolus. IDENTIFYING FEATURES: Largest of the Colletidae genera found in North America. HEAD: Like other Colletidae, Caupolicana have forked tongues. Ocelli are often enlarged. Very little malar space, giving the appearance of a short face. The first flagellar segment is elongated, approaching the length of the scape and far exceeding the length of any other antennal segment. WINGS: Jugal lobe (on the hind wing) is very long, extending at least three-quarters of the length of the vannal lobe. Also on the wing, the middle of the three submarginal cells is much shorter than the other two. LEGS: In females, the hind basitarsus is at least two times as long as it is wide. Also in females, scopa are distinctive, appearing thin and silky, as compared with other large bees with thick scopal hairs. SIMILAR GENERA: Anthophora, Habropoda, and other large Apidae may appear similar to Caupolicana. Those bees are also more likely to be seen because they fly during the daytime. Scopal hairs are on hind femur as well as hind tibia and basitarsus in Caupolicana, while restricted to lower leg sections in Apidae. Male Caupolicana do not have long antennae that extend to the end of the abdomen, as do some Apidae (e.g., Eucerini) that fly in the fall when Caupolicana is most common.

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84  Colletidae

— Caupolicana yarrowi SIZE: Large; 17–21 mm. PHENOLOGY: June through September. FLORAL HOSTS: Strong preference for flowers in the Fabaceae (Pea family). RANGE: Sonoran and Chihuahuan deserts (Arizona, New Mexico, Texas). NESTING: Nests in the ground, preferring harder packed soils than some other Caupolicana species. IDENTIFICATION: Large bee, often heard in the early morning before it is seen. HEAD: Clypeus is convex, protruding significantly from head when viewed from the side. Antennae are dark brown or black. Ocelli are larger, about the diameter of the width of the scape. THORAX: Propodeal triangle smooth, with no ridges running its width. LEGS: In males, front femur is swollen, slightly more than twice as long as it is wide. ABDOMEN: Integument is black, with bright white apical hair bands, except on T1, where hair is yellow orange. Hair T1 covered with yellow-orange hair; not the same color as bands on T2–T4 are strong the apical hair bands and continue evenly across each segment. Caupolicana yarrowi (female)

SIMILAR SPECIES: There are

only four Caupolicana species in the U.S. and Canada. Two are found in Florida, but C. ocellata occurs in the West and overlaps with C. yarrowi. In C. ocellata, the hair on T1 is the same color as the apical hair bands on T2–T4.

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T1 covered with orange/yellow hair

Caupolicana yarrowi (male)

Black abdomen with bright white apical hair bands on T2–T4

Front femur swollen; slightly more than twice as long as wide

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Colletes  85

COLLETES — SUBFAMILY: Colletinae OVERVIEW: Medium-sized bees, generally with white, gray, or brown hair on a black integument. All species are ground-nesting, and all line their nests with a clear membranous material that is waterproof. The membrane is formed by secretions from the Dufour’s gland in the abdomen. Drops of the oily substance are secreted from the gland, and a female bee quickly ingests them, then regurgitates them onto the wall using her forked, paintbrushlike tongue. The membranous “envelope” contains mostly liquid provisions, heavy with floral nectar. Eggs are attached to the wall, so that they are suspended above the liquid. Cells are constructed at night. For most species there is one generation per year, with most bees flying early in the spring or in the late fall. IN THE WORLD: Worldwide there are more than 500 species, occurring on all continents except Australia. In North America there are approximately 100 species, ranging from Florida through Alaska. CLEPTOPARASITES: Epeolus. IDENTIFYING FEATURES: Andreniform bees, usually hairy and light gray to blonde. HEAD:  The compound eyes of Colletes slant toward each other (converge), so that they are closer together at the bottom of the head than at the top. The head is usually very hairy. Subantennal suture runs from clypeus to inner margins of antennal sockets. Note that THORAX: The front half of the thorax the inner margin of the is also very hairy. At the front of the eyes slants inward, so that thorax, near the pronotal lobe, is an area the eyes appear to converge.

Notice how large the stigma is.

Colletes, like all Colletidae, have a short “tongue.” In the case of Colletes, it is also forked. The second recurrent vein (the outermost on the third “row”) is strongly curved in Colletes.

There is no pygidial plate or prepygidial fimbria in female Colletes.

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86  Colletidae

that, in some species, has a strong spine, like the point on a collar. This is called the prothoracic spine and can be a useful character in Colletes; some species have a long prothoracic spine, while it is rounded in other species. WINGS: The second recurrent vein is strongly curved. The stigma is relatively large. LEGS: Scopal hairs are on trochanters and femurs. ABDOMEN: The pygidial plate and basitibial plate are much reduced. Also, there is neither pygidial nor prepygidial fimbria. Distinguishing between the species of Colletes is difficult and requires a microscope and taxonomic keys. A handful of common Colletes are included here; note that the features associated with these species are not unique to them. Other species, not included here, may also share these characteristics; nonetheless, the characters are useful for distinguishing between the common bees included in this book. Colletes are divided into 19 groups, and reference to these group names may be seen in keys. SIMILAR GENERA: Andrena can superficially resemble Colletes. Andrena faces are more oval-shaped, with the inner margins of the eyes more or less parallel instead of converging, as in Colletes. Andrena have less hair on the front half of the thorax. Colletes carry pollen lower on their hind legs. And on the face of Colletes, there is no facial fovea near the compound eyes, nor are there two subantennal sutures. Larger species of Halictus may superficially resemble Colletes, but they have more robust heads, are usually smaller, and the wing venation is quite different.

— Colletes phaceliae SIZE: Medium

to large; 9–11 mm. through September. FLORAL HOSTS: Generalist. RANGE: Western Great Plains through to eastern Washington and Oregon and southern British Columbia, but primarily intermountain. Not found in coastal California. IDENTIFICATION: Blonde fuzzy bee of medium size. HEAD: In females, the malar space is about one-third as long as it is wide. In males, the malar space is about as long as, or a little longer than, wide. THORAX: Scutum and scutellum are covered with all light-colored hair. Scutum covered in fine, dense pits. The prothoracic spine is elongated, and very sharp. ABDOMEN: In females T1–T4 have apical bands of thick, appressed, light-colored hair, not so thick as to completely cover the tergal segment. Also in females, T1 is shiny, with just a few small pits. In males, the base of T2 is strongly indented with long white hairs. SIMILAR SPECIES: There is considerable variation in the density of the hair and punctation of the tergal segments across the range of this species. It looks very similar to C. lutzi, and this variation can make distinguishing the two very difficult. Overall, C. phaceliae is larger, and has sparser hair on the sides of each tergal segment than C. lutzi (which is less than 8 mm). Male specimens are easier, as the malar space of C. phaceliae males is long. PHENOLOGY: June

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Thorax covered with all light-colored hair T1–T4 with thick appressed apical hair bands Prothoracic spine is very sharp. Colletes phaceliae (female) Colletes phaceliae (female)

Base of T2 strongly indented Malar space is very long. Colletes phaceliae (male)

Colletes phaceliae (male)

— Colletes simulans SIZE: Small

to medium; 9–12 mm. May through October; a fall bee. FLORAL HOSTS: A specialist on latesummer and fall Asteraceae. RANGE: Widespread throughout the U.S. and southern Canada, but largely absent from the southern Great Plains. NESTING: Ground nesting. IDENTIFICATION: Moderate-sized bee with gray thorax and black-and-white abdomen. HEAD: The hair on top of the head, and on back half of thorax is often comprised of light hairs mixed with black, though this can be variable. In males, the face has long pale hairs completely hiding the clypeus. THORAX: On the scutum, there are few but distinct pits on a polished surface. The hairs are heavily branched. Propodeum is deeply and heavily pitted. In PHENOLOGY: Late

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88  Colletidae Often hidden by hair, there is an extended “tooth” on C. simulans individuals.

Punctures on the scutum are wide and deep, on a polished surface.

Note the heavily branched hairs (like a bottle brush) on the front half of the thorax. The branching pattern can aid in genus identification; all Colletes are hairy along the front half of the thorax.

Colletes simulans (female)

First segment of abdomen is females, the prothoracic spine polished, with fine punctures. Colletes simulans is wide and short, roughly (male) triangular; the size of the spine is variable in some specimens. In males, the prothoracic spine is shorter, extending out, so that the distance between the points is wider than the back of the head. LEGS: In females, the hind basitarsi are four times as long as they are Hind basitarsus wide; five times as long as wide in is five times as long as wide. males. ABDOMEN: The first tergal segment has fine, widely spaced pits on a shiny integument. SIMILAR SPECIES: Most closely resembles C. fulgidus, especially with female specimens. Differences are in the coarseness of the punctation on T1 in females, and structures on the genitalia in males. There are four subspecies of C. simulans, three occur in the West: C. simulans simulans ranges from Montana south into New Mexico and Arizona. Colletes s. armatus is mostly eastern but occurs across the northern Great Plains. And C. s. nevadensis is found in lower-elevation areas of Utah, north to British Columbia.

— Colletes slevini SIZE: Small to medium; 9–10 mm. PHENOLOGY: May through September. FLORAL HOSTS: Generalist. RANGE: Mostly in California, but extends east to Colorado and from Idaho south through Arizona. Generally at elevations over 2,500 feet. NESTING: Presumed ground nester. IDENTIFICATION: Moderate gray bee seen in the summer, sometimes in great numbers. HEAD: Malar space is roughly as long as it is wide. Flagellar segments are longer than broad. THORAX: Typically covered in light auburn, trim hair. Hair patterns can vary in males, ranging from uniformly orange to including some gray. The prothoracic spine is very short, but sharp—needlelike, rather than triangular. ABDOMEN: Usually covered

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with fine widespread punctures. Broad stripes of hair run across each tergal segment. In addition to apical hair bands, in females, T1 is covered with erect, light yellow to orange hair. And on T3–T6 there is black or dark brown hair. Colletes slevini (male)

T1 sparsely covered in erect light yellow hair

Thorax covered in thin auburn hair

T2 often with a tuft of erect yellow hair centrally

SIMILAR SPECIES: Colletes slevini is part of a group that includes C. birkmanni and C. bryanti. Males of the three are only distinguishable by looking at characteristics of the genitalia. In general, C. birkmanni is grayer, with hair on T5 and T6 being yellow, rather than black. Colletes bryanti occurs only in Arizona and New Mexico, which should help with determination.

T3–T6 have dark hair with light apical hair bands Colletes slevini (female)

— Colletes salicicola SIZE: Small; 8–9 mm. PHENOLOGY: April through June (earlier at lower elevations and latitudes). FLORAL HOSTS: Specialist on creosote bush (Larrea tridentata), but also frequents Fabaceae. RANGE: Central Mexico north to Wyoming, but more common in southern states. Eastern slopes of Sierra Nevada east to West Texas; rare across the Colorado Plateau. NESTING: Presumed ground nester.

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Long white hair on the face Colletes salicicola (female) Colletes salicicola (male)

IDENTIFICATION: Common

Long white hair on the face

T1–T3 sometimes have apical hair bands.

gray spring bee, especially in California deserts. HEAD: Long white hair on face, completely covering clypeus, and extending under the head onto the gena, especially in males. In females, hair Pits on T2 may have a slight yellow tinge. Clypeus are dense. protuberant. In males, antennae are long, dark brown, and with flagellar segments much longer than they are wide (about 1.75 times). THORAX: Covered with gray to white hair, which grows lighter posteriorly. Prothoracic spines are rounded and so short as not to be visible. ABDOMEN: On the anterior face of T1, there are relatively few hairs. In males, this contrasts with the longer white hair on T2–T5. In females, T1, T2, and sometimes T3 have apical hair bands. In both males and females, the pits on T2 are dense, and some of the pits are oblong, rather than rounded. SIMILAR SPECIES: Very similar to Colletes daleae. Females can be distinguished only by the differences in the prothoracic spines, which are present in C. daleae. Colletes daleae also has a bluish tinge to the abdomen, in the right lighting, which can help. And finally, T6 in C. daleae females has deep red/brown hairs, which is not the case for C. salicicola. In males, characters on the genitalia can be helpful, and the difference in the punctation of T2, which is sparser and without any oblong pits as in C. daleae. Males of C. daleae have shorter flagellar segments (about 1.3 times as long as wide).

HYLAEUS — SUBFAMILY: Hylaeinae OVERVIEW: Small bees, with little or no hair, and ivory markings on their face and legs. All species are twig-nesting, preferring dead stems over other materials, and all line their nests with a clear membranous material that is waterproof. Nests can also be found in

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nail holes, small-diameter beetle burrows, and abandoned nests of other bees. Pollen is carried back to the nest internally in a crop, instead of in scopal hairs. Nectar is also carried in the crop, resulting in a provision that is soupy. Pollen preferences are not known, as it is difficult to determine when pollen is carried internally. There is evidence that some species may prefer plants in the Rosaceae family. Seven Hylaeus species endemic to Hawaii are listed as endangered. IN THE WORLD: Found worldwide, including many larger island groups (in the U.S., notably Hawaii). There are more than 700 species around the world. In mainland North America there are around 50 species, 45 of which can be found in the Midwest, southern Canada, and western states. CLEPTOPARASITES: Unknown, but a few species in Hawaii appear to be cleptoparasitic on other Hylaeus species. IDENTIFYING FEATURES: Distinct, though small, bees; body is hairless with ivory markings, most prominently on face and leg joints, and more extensive in males. Males tend to be easier to identify to species than females. HEAD: Ivory markings are often next to compound eyes, but may extend onto clypeus, or may be absent entirely. Along each compound eye there is a narrow but deep groove (fovea). There is one subantennal suture. THORAX: The scutal surface is usually heavily pitted and roughened. WINGS: There are two submarginal cells. The basal vein is relatively straight. ABDOMEN: There are no pollen-collecting hairs. Distinguishing between species is complicated by the significant variation in characteristics within a species. What’s more, it is likely there are many undescribed species in the West whose characteristics don’t fit with the descriptions currently known. We have included a few common species, of the 45 found in the West, but verification with a key and a reference collection may be needed for certainty. Remember that female Hylaeus appear similar to males because they lack scopal hairs. Count antennal segments to be certain of sex: males have 13 segments, while females have 12. SIMILAR GENERA: Small Halictidae (small Halictus, Dufourea) may appear superficially similar to this colletid. The Hylaeus body shape is narrower when viewed from above, and the body is usually marked with ivory or yellow markings. Halictidae are not similarly marked, the body shape is flatter, and most have three submarginal cells. Additionally, many Halictidae have metallic tints on the thorax, while Hylaeus are matte black.

— Hylaeus leptocephalus SIZE: Petite to small; 4–6 mm. PHENOLOGY: April through October. FLORAL HOSTS: Unknown, but appears to prefer legumes, especially the introduced Melilotus. RANGE: East coast to west, though absent from the southern states of the Midwest and the Gulf Coast. Recently introduced to Hawaii. This species may be one that was introduced to North America in the early 1900s. NESTING: Nests in preexisting cavities and readily nests in artificial nesting sites like buildings or straws. IDENTIFICATION: Small black bee, with generous yellow on face. May be very abundant when seen. HEAD: The head narrows toward clypeus. In females, pale yellow marks fill

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the area between the clypeus and the compound eyes, ending suddenly at the level of the antennae, but the clypeus is black. The facial fovea is a very short line, appearing almost as a pit, rather than a groove. In males, the face is entirely yellow below the antennae, and yellow also extends in a lobe up beside the compound eye, as well as between the antennae. Also in males, the scape, which is narrow, has a yellow stripe on the ventral surface. THORAX: The pronotal collar has yellow markings. The scutum is extremely coarse, with pits being much bigger than those on the top of the head. Between pits, the integument is dull and roughened. The propodeum has a strong carina running around it. In males, the tegulae are yellow, though they are browner in females, growing yellow anteriorly. LEGS: In females, tibiae are yellow only at their bases, and the rest of the leg is black. In males, the front tibiae are mostly yellow, as is the end of the femur, the bases of the mid and hind tibiae, and the mid and hind basitarsi. SIMILAR SPECIES: This species might be the same as the European bee H. bisinuatus (possibly introduced to North Dakota in early 1900s and spread across the country). Tegulae are brownish, growing yellow anteriorly.

Yellow on the face ends near the level of the antennae. The clypeus is black.

Hylaeus leptocephalus (female) Some yellow on the pronotal collar Scape has a yellow stripe on the ventral surface

Hylaeus leptocephalus (male) Face entirely yellow below the antennae with yellow extending up centrally and along the compound eyes

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— Hylaeus mesillae SIZE: Petite; 3–4 mm. PHENOLOGY: Late June through October. FLORAL HOSTS: Polylectic, but commonly seen visiting summer-blooming Apiaceae. RANGE: Across the U.S. and Canada, from Nova Scotia to British Columbia and south to Georgia, southern Texas, and Arizona. NESTING: Twig-nesting but will also use nail holes and other small cavities. IDENTIFICATION: Extremely small but common matte-black bee. There is a gradation in coloring across the U.S., with western and southern individuals exhibiting more yellow than eastern and northern specimens. HEAD: In females, the clypeus is black, with maybe a small ivory mark; yellow runs up beside compound eyes, rarely extending beyond antennal sockets. In males, the antennal scape has some yellow, as does the clypeus and the areas beside the compound eyes. The first flagellar segment is much shorter than the second flagellar segment. The fovea, running next to the compound eye, is long and linear, extending from its top halfway to the antennal sockets. THORAX: The pronotal collar of both males and females is black. On the scutum, pits are small and shallow (not very noticeable). In both sexes, tegulae are black. LEGS: The front tibiae usually have ivory to yellow markings.

Scape is yellow underneath.

Pronotal collar is black.

Hylaeus mesillae (male)

Tegulae black Hylaeus mesillae (female) Yellow clypeus Yellow next to each eye curves away from eye above antennal socket.

Black pronotal collar Tegula mostly black Black clypeus (some individuals may have a spot of yellow in the middle).

Yellow on face runs up beside compound eyes, rarely extending beyond antennal sockets.

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Hylaeus mesillae (female)

Tibia with extensive yellow markings.

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SIMILAR SPECIES: Hylaeus annulatus has only a small yellow spot on the tibia, and the bee is larger than H. mesillae. In the Midwest, Hylaeus rudbeckiae (not shown here) overlaps and looks similar. Between the two, H. mesillae is much more abundant. Hylaeus rudbeckiae is slightly larger with a wider head. The yellow markings are more extensive overall, and are usually more yellow/orange, while H. mesillae is more ivory colored, and less extensively marked. Hylaeus saniculae, another rare Hylaeus, also looks similar to H. mesillae but lacks the extensive yellow markings on the tibia; on the face it has a yellow line across the base of the clypeus.

— Hylaeus megalotis SIZE: Petite to small; 4–5 mm. PHENOLOGY: April through September, depending on latitude. FLORAL HOSTS: Presumably a generalist. RANGE: Common in the Rocky Mountains, and south through Texas. Absent further east or west. NESTING: Nests in preexisting cavities, often in hollow plant stems. IDENTIFICATION: HEAD: In both sexes, the head is about as wide as it is long. In females, there is a very elongated apical mandibular tooth, which is distinctive and not found in other Hylaeus species. THORAX: In females, the pronotal collar is yellow all the way around its edge, rather than interrupted in the center with black. Yellow pronotal collar ABDOMEN: In males, T1 has sparse fine punctures.

Hylaeus megalotis (female)

Hylaeus megalotis (male)

T1 with sparse fine punctures

Yellow pronotal collar

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SIMILAR SPECIES: Males of this species appear similar to H. asininus, but the head is narrower in H. megalotis, and T1 has larger and denser pits in H. asininus.

— Hylaeus basalis SIZE: Small; 8–9 mm. PHENOLOGY: May through August. FLORAL HOSTS: Generalist, but appears to prefer Rosaceae. RANGE: Widespread across the U.S., but more common in mountainous regions and western states. Rare in the Great Basin and Chihuahuan and Sonoran deserts, where it occurs only at higher elevations. NESTING: Nests in twigs and other preexisting cavities. IDENTIFICATION: Nearly all-black small bee. HEAD: In female, face is completely black, and round, as malar space is extremely short. Supraclypeal area has thin fine ridges, but no punctation. The head is broad. On the mandible there is an elongated apical tooth that is distinctive. In males, clypeus and area to each side of clypeus are yellow, as is the area above the clypeus; the clypeus is longer than it is wide but does not protrude noticeably from the face. Most notably, the scape in males is All-black face and body extraordinarily enlarged, and the Hylaeus basalis anterior half is a light orange/yellow (female) color. THORAX: Completely dark in both sexes, with punctation deep and close over a dull integument. The pronotal collar is an even width all the way around.

Hylaeus basalis (female)

Scape extraordinarily enlarged with anterior half light yellow-orange

Hylaeus basalis (male)

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96  Colletidae LEGS: Some markings occur on legs in males. ABDOMEN: With coarse punctation, over a dull integument. SIMILAR SPECIES: The only other Hylaeus with a scape as enlarged as in this species is the closely related H. nunenmacheri. The latter is found only in West Coast states and is smaller. It appears more polished overall, has a shorter clypeus.

— Hylaeus wootoni SIZE: Small; 4–5 mm. PHENOLOGY: June through September. FLORAL HOSTS: Presumed generalist; seen frequently on open shallow flowers, with many individuals collected on Eriogonum and Solidago. RANGE: Western states, from Nebraska to the Central Valley of California, and western Texas north to southern British Columbia. IDENTIFICATION: Highly variable, but very widespread bee. HEAD: Wider than it is long. In females the facial fovea is short, and the clypeus lacks any yellow markings. In males, the supraclypeal area is almost completely square. THORAX: The pronotal collar is yellow only on the sides, and not dorsally. There is no carina around the propodeum. The scutum is densely pitted, with pits close together. ABDOMEN: In females, T1 is densely and distinctly punctate, with a smooth and polished integument between. SIMILAR SPECIES: Though common, this bee is difficult to identify with confidence. It appears most similar to H. coloradensis and H. polifolii. Female H. coloradensis are larger, and in males the supraclypeal area is elongated, rather than square as it is in H. wootoni. Female H. wootoni and H. polifolii are about the same size; in H. polifolii there is a yellow spot in the middle of the clypeus, while the clypeus of H. wootoni is all black. In males, the supraclypeal area of H. wootoni is usually yellow, Pronotal collar yellow whereas it is usually black only on sides in H. polifolii.

Pronotal collar yellow only on sides

Hylaeus wootoni (male)

Hylaeus wootoni (female)

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Supraclypeal area a yellow square

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ANDRENIDAE

Andrenidae is a diverse family, very common in North America, that includes this continent’s smallest bees and some of the biggest as well. Morphologically, the diversity of form is phenomenal, including all-yellow bees, solid black bees, some species with sky blue eyes, and very hairy bees. All are solitary, though aggregate nesting and communal nesting occur. All species nest in the ground. Among North American species are a large proportion of specialists as well as many generalists. There are no cleptoparasitic bees in the Andrenidae. The smallest bee north of Mexico (and maybe the smallest bee in the world) occurs in this family. Perdita minima is less than a tenth of an inch in size (2 mm). It lives in the Mojave, Chihuahuan, and Sonoran deserts, and specializes on Euphorbiaceae. IDENTIFICATION: At the family level, Andrenidae are diverse; characters that unite the family are not immediately evident. HEAD: Almost all bees in the family Andrenidae have two subantennal sutures (a few male Protandrenini have just one). The two subantennal sutures are a feature not found in any other bee family. THORAX: Bees in the genus Andrena, in the family Andrenidae, collect pollen in propodeal scopa, on the posterior end of the thorax. LEGS: On the legs, female Andrenidae collect much of their pollen on the femur and even the trochanter, as opposed to mostly on the tibia, as seen in bees in, for example, Apidae. While other bees will collect pollen on the femurs like andrenids, seeing scopae, and often pollen, high on the leg of a bee is a clue that it might be an andrenid. TAXONOMY: There are more than 3,000 species and 45 genera in the world; though they occur on every continent but Australia, they reach their highest richness in the Northern Hemisphere, especially North America. Here, there are more than 1,200 species in 11 genera. Andrenidae in North America occur in three subfamilies, all of which are well represented in the West. Characters distinguishing them are often on the genitalia or the smaller sternal segments, in males. These

All Andrenidae have two subantennal sutures.

The episternal groove can be difficult to see in hairy species, yet its size and shape can be diagnostic of some genera in Panurginae.

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characters are not included in our descriptions. Of note here is the episternal groove, whose shape and presence distinguishes between tribes in the Panurginae.

—  SUBFAMILY ANDRENINAE There are three genera in this subfamily. All three have deep facial foveae, which are depressions running vertically next to each compound eye, filled with dense woolly hair. Ancylandrena, Andrena, Megandrena

—  SUBFAMILY PANURGINAE

Facial foveae

Six genera occur in this subfamily, and all can be found in western states and provinces, though some are not common. They are divided into three tribes. The characteristics distinguishing the tribes are not always easy, though the genera are not hard to tell apart. All Panurginae collect pollen on the tibia, and it is usually a wetter mass, rather than the dry pollen seen in other Andrenidae. — CALLIOPSINI: There is only one genus in North America: Calliopsis. On the head, there are yellow markings on the faces of both males and females, especially on the clypeus and supraclypeal area. The thorax is usually polished, but not metallic. Though hard to see, the episternal groove on the side of the thorax is short. On the wing, there are two submarginal cells. — PANURGINI: All Panurgini have two submarginal cells. The episternal groove is absent or extremely reduced and curving into the scrobal groove. There are three genera, in different subtribes, in North America. All occur in the West. Macrotera was once a subgenus of Perdita. Differences are in the mandibles; Macrotera has a groove that angles across the entire length of the mandible. The heads of males are often extraordinarily rectangular in shape. Panurginus. On the thorax, there is no episternal groove. In males, the legs and the clypeus are often yellow. On the abdomen, T2–T5 are usually hairy along margins. Perdita. Minute bees with flattened appearance, especially the abdomen. On the thorax, the episternal groove is short and curves backward toward the scrobal groove. Not very hairy, but may be yellow, metallic greenish blue, or polished black. On the wing, the marginal cell is extremely truncate. Also, the veins on the wing are often ivory or white. — PROTANDRENINI: There are two genera in Protandrenini united by their long episternal groove. They may have two to three submarginal cells, and a moderately truncate marginal cell. Slender, longer bees. Males always have yellow on the face. Protandrena and Pseudopanurgus are dark, mostly hairless bees. They may have two or three submarginal cells. Females are all black, but males have yellow on face,

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antennae, and some leg joints. These two groups were historically separate genera, but there is considerable overlap in appearance; recent genetic analyses show that they may not be separate. Anthemurgus is not covered in this book.

—  SUBFAMILY OXAEINAE Two genera occur in North America, but only along the border with Mexico: Protoxaea and Mesoxaea (not covered in this book).

ANCYLANDRENA — SUBFAMILY: Andreninae OVERVIEW: Fuzzy, quick-flying, medium-sized bees seen in the spring. Ancylandrena are secretive bees and have been relatively seldom studied. One species appears to fly at dawn and has enlarged ocelli, while others fly throughout the day. One species is a specialist on Larrea tridentata (A. larreae), two specialize on plants in the Fabaceae, and one appears to be a generalist. Nesting has been studied for one species, and it is presumed that all species nest in the ground as that one does. IN THE WORLD: Five species exist; all are centered in western North America, extending south only so far as northern Mexico. CLEPTOPARASITES: Hexepeolus. IDENTIFICATION: Gray to tan larger bee; males fly especially fast and can be hard to observe on flowers. HEAD: Clypeus is moderately to strongly protuberant. In males the clypeus is often black, but the paraocular area next to each compound eye may have modest yellow markings. There are two subantennal sutures and velvety facial foveae in wide grooves beside compound eyes. LEG:  In both sexes, the hind coxa is shortened. In females, the hind trochanter has hairs that are dense and short. WINGS: There are three submarginal cells. ABDOMEN: The anterior face of T1 is widely depressed, creating a notable concavity. Males have a large, distinctive pygidial plate compared with other Andreninae. SIMILAR GENERA: Ancylandrena may appear similar to other Andreninae. Females can be distinguished from both Megandrena and Andrena by the wide depression in the anterior face of T1 in females. In males, the hind basitarsus is much narrower than in Andrena, and the mandible has a preapical tooth on the upper margin, which is missing in Megandrena males.

— Ancylandrena larreae SIZE:

Medium; 10–14 mm. PHENOLOGY: Early spring, March through early June. FLORAL Appears to specialize on Larrea tridentata (creosote bush). RANGE: Hot deserts, centered in the Mojave and Sonoran deserts, but north as far as Utah and east to New Mexico. NESTING: Ground nester in loose soils; entrances often partly hidden by plants. HOSTS:

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IDENTIFICATION: Striking bee with tan hair and black abdominal stripes. HEAD: Clypeus protrudes notably from face and is slightly elongated. Eyes are parallel. The second flagellar segment is the same length as it is wide, or slightly longer than it is wide. In males, there is a slight cream-colored mark in the paraocular area next to each eye. On the mandible, there is a rounded Ancylandrena larreae (female) protrusion near the base; it is Anterior face of T1 has a wide depression larger in females and yellow in color. THORAX: Covered in pale white Tan hairs across the scutum, scutellum, thorax and propodeum, and down the sides of the body. LEGS: In females, scopal hairs are light yellow to light tan in color, but near the basitibial plate there is a Facial fovea small patch of dark hair. deep brown ABDOMEN: In females, there are scopal hairs on S1–S4, and they are Black abdomen with white hair bands long on all four segments. SIMILAR SPECIES: There are five species of Ancylandrena, and they may be difficult to distinguish from each other. Distribution and Cream-colored mark floral associations can help some: next to each eye Ancylandrena rozeni has been seen only in mountains near Tucson, AZ. Ancylandrena larreae, specializing on creosote bush (Larrea tridentata), is the most widespread, and is the only species that makes it as far east as New Mexico. Only it and Ancylandrena timberlakei (which also specializes on Ancylandrena larreae creosote) make it as far north as Utah. (male) Between the two, A. larreae has lighter scopal hairs on hind basitarsus, as well as scopal hairs on S1–S4, while these hairs exist only on S1–S2 in A. timberlakei, a species in which scopal hairs are a dark gray. The clypeus protrudes strongly in this species, as it does in A. larreae. Ancylandrena atoposoma is associated most with Lupinus; it has lighter scopal

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Andrena  101

hairs on the hind tibia and basitarsus and a short clypeus that doesn’t protrude far. Finally, Ancylandrena koebelei flies at dawn and has enlarged ocelli and, in males, the clypeus is off-white. In both sexes, there is a large bump at the base of the mandibles.

ANDRENA — SUBFAMILY: Andreninae OVERVIEW: Petite, slender bees, often delicate-looking; ubiquitous in western North America. Variable hair patterns ranging from rusty red to black. All species nest in the ground and are often seen in early spring, though a suite of species also flies only in the fall. Many species nest in aggregations, and patches of disturbed earth at the nesting site are often one of the earliest signs of bee activity in the spring. Includes many specialists, though some species are generalists. IN THE WORLD: Found worldwide with more than 1,500 species, but absent from South America and the South Pacific. In North and Central America, they are found as far south as southern Mexico, with more than 500 species in the U.S. and Canada. There are around 400 species in the western states. Andrena have been subdivided into 47 subgenera in North America (we address several, but not all, below). CLEPTOPARASITES: Nomada. IDENTIFYING FEATURES: Identifying a bee as an Andrena is relatively easy with a microscope but can be more challenging in the field. Overall, the Andrena bee body is flat. HEAD: Deep grooves run next to each compound eye, filled in with thick woolly hair. These “vertical eyebrows” are called facial foveae. Running from each antennal socket to the top of the clypeus are two sutures (subantennal sutures). The compound eyes are parallel to each other. In males, the clypeus and paraocular areas are often yellow. Mandibles of males are generally elongated and cross in the front. Also in males, the malar space is usually much wider than it is long. THORAX: Many species have an elongated pronotal collar, giving the appearance of a “neck.” Worth mentioning, for the student of bee taxonomy who would like to try their hand at using one of the bee keys referenced at the end of this section, is the humeral angle of the pronotum, referred to in many taxonomic keys. The pronotal collar connects the head to the thorax. This structure may be sharply angled or rounded and indistinct. If it is rounded (tubular), the humeral angle is weak; if it is sharply edged (like a long rectangle), the humeral angle is strong. It is not always visible without a microscope and a specimen that can be turned in different directions.

The humeral angle of the pronotum is often used to identify different Andrena to species, though this characteristic is not often visible without a microscope.

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102  Andrenidae LEGS: Scopal hairs run up onto the trochanter, in addition to the femur, and in some cases to the propodeum. ABDOMEN: Is often shiny and has a distinctive oval shape, tapering at either end. With more than 500 species in North America, Andrena are notoriously difficult to identify to species, even by experts. They may be one of the most difficult groups included in this book. To add to the difficulty, the sexual dimorphism in Andrena is extreme, so that males and females look very different from each other. Many Andrena are specialists, limiting themselves to certain groups of flowers when collecting pollen for their offspring. Knowing the flower on which an Andrena was seen can help narrow down which species it is. Identifying the subgenus can also help, though subgeneric characters are not always easy to see either. Below we provide information about some common species, but see keys listed at the end of this book for affirming identification. SIMILAR GENERA: Colletes are probably the easiest to confuse with Andrena as they are the same size and share a similar body shape. The wing venation of Colletes, with the curved second-recurrent vein, differs from the straight second-recurrent vein of Andrena. The head of Colletes is heart-shaped, as the inner margins of the compound eyes converge near the bottom. The inner margins of the compound eyes in Andrena are parallel.

— Andrena milwaukeensis SIZE: Small

to medium; 8–12 mm. through July. FLORAL HOSTS: Polylectic. RANGE: Widespread throughout North America; from coast to coast in northern states (Alaska and Northwest Territories, south to Washington and Oregon to New England and Nova Scotia), but largely absent from the Southwest. IDENTIFICATION: An eye-catching red-orange bee. HEAD: On the mandible, there is a small tooth at the base. The clypeus is elongated, though flat, with sparse, irregular punctation. In females, the face is long, due to long malar spaces (three times as long as wide). Also in females, the facial foveae are wide at the top, narrowing and ending above the antennal sockets, filled with brown hair. In males, the face is not as long, with the malar space short and wide. The clypeus is flat, and the first flagellar segment is relatively long. THORAX: In females, red-orange hair is abundant, obscuring the pronotal humeral angle and ridge, which are not prominent, and the pronotal collar is not elongated. In males, hair is sparser and a lighter brown, and the scutum and scutellum are roughened, as if with sandpaper. LEGS: Tibial scopal hairs are long and simple, and dark brown to black. WINGS: The first recurrent vein hits the second submarginal cell very near where it meets the third submarginal cell. ABDOMEN: In females in the West, long red hair occurs on T1–T4; T5 and T6 have dark hair. Tergal segments are dull, with very small shallow punctation. The pygidial plate is rounded at its apex. In males, the basal hairs on T3–T5 are all brown to black. PHENOLOGY: April

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Andrena  103

Andrena milwaukeensis (female)

The scopal hairs are unbranched and dark.

Red-orange hair on thorax and T1 and T2 is unique in Andrena milwaukeensis.

Andrena milwaukeensis (male)

SIMILAR SPECIES: There are two subspecies of A. milwaukeensis that intergrade in the northern parts of the U.S. and in Canada. The more eastern form does not have long red hair extending past T2 in females like the western form does. Andrena perarmata has reddish hair on the tergal segments as western A. milwaukeensis does; in the former, though, the punctation on the clypeus is small and crowded near the center, and the hair on T1–T4 is yellower, instead of the red found in A. milwaukeensis. Also, Andrena perarmata is a willow specialist, and seldom seen on other plants. Andrena clarkella is also fox red on the thorax, but the abdomen has no red hair; it overlaps with A. milwaukeensis in Canada and Alaska.

— Andrena frigida SIZE: Small to medium; 9–12 mm. PHENOLOGY: Early spring; March through June depending on latitude. Often seen before the snow is completely melted. FLORAL HOSTS: Specialist on willow (Salix) but can be observed on other early spring–blooming shrubs and trees, including dogwood (Cornus) and early blooming fruit trees (Prunus). RANGE: Pacific coast to New England, largely absent from Gulf Coast and southern Midwest. NESTING: Ground nesting. IDENTIFICATION: Medium-sized ghostly white bee seen on willow (Salix) in the spring. HEAD: Covered in long white unkempt hair, covering the clypeus like a mustache in males. There is no basal tooth on the mandible. The malar space is relatively short, so the head is broad, wider than long in both sexes. The clypeus is roughened, with

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104  Andrenidae

Thorax and abdomen covered with long white unkempt hair

Second submarginal cell shorter than the third

Scopal hairs white, longer on femur than tibia Andrena frigida (female)

small, crowded pits. In females, facial fovea is large, shallow, and extends below the antennal sockets; it has dark brown/black short hair. In males, the first flagellar segment is one and a half to two times as long as the second segment. Also in males, the clypeus is dark. THORAX: The scutum is dull, Tergal segments not shining; pits are present, but hard lack distinct pits. to distinguish. The hair is usually pale, light white, concentrated on the sides of Andrena frigida (male) the thorax, with some mixed dark and straw-colored hairs on the dorsal surfaces. WINGS: The second submarginal cell is much shorter than the third, so that the first recurrent vein is beyond the middle. LEGS: Scopal hairs are pale white, longer on the femur than the tibia. ABDOMEN: The tergal segments are almost impunctate, lacking in many distinct pits. Long white hairs cover each tergal surface, though not so dense as to obscure the surface and not creating distinct hair bands. SIMILAR SPECIES: Andrena frigida is a variable species; described above is the typical pale-haired form, but some specimens have mostly dark brown or black hair. Appears similar to Andrena perarmata, which is also a willow specialist. Andrena perarmata has a basal tooth on the mandible, which is not the case for A. frigida. Andrena perarmata also has a longer malar space than A. frigida, denser punctation on the clypeus, and more distinct pits on the tergal segments, which have longer hairs, than are seen in A. frigida.

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Andrena  105

— Andrena crataegi SIZE: Small

to medium; 8–11 mm. through July. FLORAL HOSTS: Polylectic; may have some slight preference for Rosaceae. RANGE: Abundant west of the Rocky Mountains and can be the dominant Andrena species in some areas. Rare in the Midwest, but common in eastern states, especially the Northeast. Ranges from British Columbia to Quebec in Canada. NESTING: Communal, with many females sharing the same nest entrance or tunnels, but with separate cells inside. Nests have been found with up to four entrances. IDENTIFICATION: Striking black bee with minimal hair. HEAD: The clypeus is entirely black; there are tiny deep pits irregularly spaced. In females, facial foveae are wide and long, extending from the top of the compound eye to the antennal sockets. Also in females, the flagellar segments are slightly rust colored. In males, the antennae are long, reaching almost to the propodeum when stretched back across the body. THORAX: Very dull due to a roughened integument, though the pits are deep and hard to miss. A line of auburn hair outlines the scutum. The pronotal collar is elongated, but there are no pronounced humeral angles. Tegulae are often reddish. WINGS: Slightly tinted, like amber glassware from the 1970s. LEGS: The hind tibial spur is strongly curved, with a flattened base and thinning to the point of being nearly PHENOLOGY: May

Andrena crataegi (male)

The pronotum and pronotal collar are elongated, but there are no ridges or strong angles at the edge that meets the thorax.

The hind tibial spurs are unique: flattened at the base, but tapering to a fine, almost transparent point, and bent in the middle.

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Andrena crataegi (female)

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106  Andrenidae

see-through. In females, scopal hairs appear sparse because they are simple and unbranched. Also in females, and hard to see, there is a strong ridge running along the back surface of the hind femur. ABDOMEN: There are no hair bands, but the tip of the abdomen is lined with auburn hair, the same color as the thorax. In females, the pygidial plate is V-shaped with a rounded tip. In males, the apical margin of S6 folds back on itself, especially laterally. SIMILAR SPECIES: Among western Andrena, male A. crataegi appear most similar to A. argemonis. Characters of the sixth sternal segment can help: in A. argemonis S6 is not folded back on itself. The carina on the hind femur of A. crataegi females is unique; that combined with the all-black integument should distinguish it from all others.

— Andrena helianthi SIZE: Medium; 11–12 mm. PHENOLOGY: Late summer; mid-July through September. FLORAL HOSTS: Specialist on Asteraceae (Sunflower family), with a strong preference for Helianthus. RANGE: East of the Sierra Nevada range to the Atlantic coast. Absent in the Southeast and Texas. In Canada, Alberta to southern Quebec and north to central Manitoba. NESTING: Ground nester. IDENTIFICATION: Larger blonde Andrena seen on sunflowers in the fall. HEAD: The head is wider than long, with the malar space almost nonexistent. In females, the clypeus is shiny, black, and moderately protuberant. In males, the clypeus is polished yellow, and protrudes slightly. THORAX: Covered in vibrant strawberry blonde hairs, nearly obscuring the scutum. Pits are shallow and irregular on the roughened scutal surface. The tegulae are amber colored. In females, the propodeum is surrounded by longer hairs, and the area may serve to hold harvested pollen. Also in females, the pronotal collar is moderately produced, but lacks Propodeum surrounded strong humeral angles. by longer hairs Thorax covered with strawberry blonde hair WINGS: Second recurrent vein hits second submarginal cell at its center. LEGS: In females, scopal hairs are similar in color to the hair on the thorax. Males have red-yellow Black abdomen tarsal segments. with weak blonde hair bands ABDOMEN: Black in both Andrena helianthi (female) sexes, and heavily roughened so there is no polish. Pits are

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Andrena  107

Andrena helianthi (male)

Clypeus yellow

few, minute, and shallow. In females there may be weak, blonde-colored hair Tarsal segments bands on each tergal segment. red-yellow SIMILAR SPECIES: In the West, A. helianthi looks similar to A. vulpicolor. Females of the latter are slightly larger (12–15 mm), and the tergal segments have much denser hair bands than in A. helianthi. With a microscope, it might be possible to see the very large labrum in A. vulpicolor as well; it is very short in A. helianthi. In males, the flagellar segments are usually darker in A. vulpicolor, and there is a broader white hair band on T1.

— Andrena cerasifolii SIZE: Small to medium; 8–13 mm. PHENOLOGY: January through March and May through June; likely two generations per year. FLORAL HOSTS: Generalist that visits a wide array of spring-blooming plants. RANGE: West of the Rocky Mountains, primarily in southwestern states and California. NESTING: Ground nesting. IDENTIFICATION: Stunning, rather large, shiny blue-black bee seen in the spring. HEAD: Blue-black integument with white hairs, especially near clypeus. The clypeus is densely punctate. In females, facial foveae are long and broad, approaching the simple eyes and extending down past antennal sockets. Hair in facial foveae is thick and

Metallic blue/black integument with white hairs and dense punctation

Andrena cerasifolii (female)

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108  Andrenidae Andrena cerasifolii

Antennae long, reaching

black. Gena is about as broad as (male) back to the scutellum the eye, and malar space is short. Dark metallic blue In males, antennae are long, thorax and abdomen reaching back to scutellum. THORAX: Metallic blue-black or green. The scutum is heavily pitted with distinct pits covering its roughened surface. WINGS: A little dusky, especially in males. Second recurrent vein hits second submarginal cell at its center. LEGS: In females, scopal hairs are mostly white, with some dark hairs on the femur. In some specimens, scopal hairs are all dark. ABDOMEN: Metallic blue/green with dense coarse punctation. Hair bands are minimal, though sparse white hair is present on each tergal segment in both males and females. SIMILAR SPECIES: Andrena impolita females look very similar to Andrena cerasifolii females, but A. impolita is restricted to California and Arizona. In general, the punctation on the tergal segments of female A. impolita is smaller, and duller, with more pits. The male of A. impolita has a longer first flagellar segment.

— Andrena lupinorum SIZE: Medium; 11–14 mm. PHENOLOGY: May through August. FLORAL HOSTS: Observed on many plants, but most records are from Fabaceae (Pea family); it is likely a specialist on this family. RANGE: Primarily higher-elevation areas in mountains from New Mexico and California north to southern Canada. East across the plains, but more common in northern plains states than southern. NESTING: Ground nester. IDENTIFICATION: Starkly contrasting black-andblonde bee. HEAD: Black integument, even on clypeus in males. Clypeus is very coarsely punctate. Dark hairs cover most of the face, except for some orange on the vertex and near the antennal sockets. In females, facial fovea is shallow, elongated, extending down below the antennal sockets, filled with short dark brown hairs; in some specimens the hair becomes lighter near the vertex. When viewed straight on, the vertex is tall, extending up behind the lateral simple eyes. THORAX: Orange to blonde hairs cover the scutum, scutellum, and metanotum, but they often grow darker down the sides of the thorax. LEGS: In females, scopal hairs are black. ABDOMEN: In both males and females, black hairs cover the entire abdomen evenly, so that no hair bands are present. Deep distinct pits occur across the surface.

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Andrena  109 Black head with some light hairs on the vertex Fovea brown Thorax in some specimens is a dark orange.

Andrena lupinorum (male)

Thorax covered with blonde hairs with darker hairs on the sides (especially near propodeum)

Andrena lupinorum (female)

Abdomen covered in short black hairs with no light hair bands

SIMILAR SPECIES: Andrena lupinorum bears a strong resemblance to A. vicina, which occurs throughout the northern half of its range (and extends further north beyond). In both sexes, the clypeus is less coarsely punctate in A. vicina. In females, the hair on the thorax of A. vicina, while of the same color, is shorter. Additionally, and hard to see, A. vicina has a groove down the middle of the labrum (under the clypeus), which is lacking in A. lupinorum. In males, the antennae of A. lupinorum have a longer first flagellar segment.

— Andrena prunorum SIZE: Medium; 12–14 mm. PHENOLOGY: April through July, depending on latitude and elevation. FLORAL HOSTS: Generalist. RANGE: In Canada, British Columbia, Alberta, Manitoba. South in the U.S. to the Mexican border. California east to Colorado. NESTING: Ground nester. IDENTIFICATION: Striking, very common Andrena; red-and-orange abdomen with smoky wings. HEAD: In females, facial foveae extend below the level of the top of the clypeus, and up to the lower edge of the simple eyes. Also in females, the clypeus can be either yellow or dark. In males, the clypeus is yellow, as are the paraocular areas to either side of the clypeus. THORAX: Black with sparse orange/tan hairs. Scutum has deep round pits, moderately spaced. On the sides of the body, there are large, almost touching pits,

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110  Andrenidae

Andrena prunorum (male)

Yellow clypeus

Highly variable species; some individuals are entirely dark. T2 and T3 often red-orange

Andrena prunorum (female)

separated from each other by sharp ridges. In females, tegulae may be dark reddish brown to yellow red. WINGS: Dusky wings, often with reddish veins. In males, there is no strong carina enclosing the propodeum. Smoky wings LEGS: The tarsal segments and tibiae are with red veins bright red to orange. In females, the scopal hairs are brown, white, and pale yellow intermixed. ABDOMEN: Variably colored in females, often with T2 red or orange. In some individuals, the tergal segments are yellow-brown, all yellow, or with narrow red bands on the apical areas of some tergal segments. In all individuals there are light, inconspicuous, apical hair bands. Red-orange abdomen, In males, T2 and often T3 have a red band particularly on T2 just above the apex, or are entirely red. SIMILAR SPECIES: This species is highly variable in coloration, being entirely dark, or distinctly red-hued; two subspecies exist (A. prunorum prunorum and A. prunorum sinaloa), but even within the two subspecies there is considerable diversity in coloring. Dark morphs of Andrena prunorum look similar to A. crataegi; the larger, deeper, more contiguous pits on the side of the thorax should distinguish all varieties of A. prunorum from A. crataegi. In addition, the usually yellow clypeus of males and most females, and the often red legs are distinctive. Andrena argemonis looks similar in the reddish form; it is a specialist on prickly poppies (Argemone) in the desert Southwest. In the area where they overlap, the hind femur in females differs in A. argemonis in that it has a strong ridge on the apical half; this is absent from A. prunorum individuals. Andrena argemonis males have a strong carina enclosing the propodeum.

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Andrena  111

— Andrena angustitarsata SIZE: Small

to medium; 8–10 mm. spring; March through early May. FLORAL HOSTS: Generalist. RANGE: Central British Columbia south to northern Mexico east to Colorado and Nebraska. NESTING: Ground nester. Overwinters as an adult to emerge very early in the spring. IDENTIFICATION: Extremely common slender Andrena seen in the early spring. HEAD: Clypeus is dull, roughened as if with fine sandpaper. In females, the lateral simple eyes appear close together, concentrated on the top of the head, because of the longer vertex; more than one ocellus’s width from the back of the head, and more than one from the top of the facial fovea. Also in females, the facial fovea is broad, shallow, filled with brown hair. THORAX: There is no strong pronotal angle. The scutum is roughened, with some sparse punctures barely visible. The propodeum is very narrow. WINGS: Very slightly tinted yellow, with redbrown veins. LEGS: In females, scopal hairs on the hind tibia are short; brown near the apex of the segment, and lighter near the base. Those hairs on the trochanter are very short at the base, but longer near the apex. Also in females, the basitarsus is broader at the apex (toward the tarsal claws) than at the base. ABDOMEN: In both sexes, there are no or few pits on the tergal segments; though they are roughened, and not at all translucent. Apical areas are often translucent, dark red brown near the base. Andrena angustitarsata In females this can be hidden (male) on T2–T4, which have pale white apical hair bands. SIMILAR SPECIES: Andrena nasonii looks very similar to A. angustitarsata and emerges during the same season. In A. nasonii, the lateral ocelli are more widely spaced, so that they are less than an ocellus’s width from the back of the head, and from the facial fovea. PHENOLOGY: Early

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Facial fovea broad and filled with brown hair

Andrena angustitarsata (female) Pale hair bands on T2–T4

Abdomen lacks clear pits.

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112  Andrenidae

MEGANDRENA — SUBFAMILY: Andreninae OVERVIEW: Larger bee that looks very similar to Andrena. Generally fairly hairy. Rarely seen as there are only two species, both restricted to hot desert regions of North America. The two species are specialists, with one visiting Mentzelia (blazing star) and the other Larrea (creosote bush). Presumed to be ground nesters. IN THE WORLD: Megandrena are restricted to the Mojave and Sonoran deserts in North America. There are two species. CLEPTOPARASITES: Unknown. IDENTIFICATION: Similar to the more common Andrena, but larger. HEAD: Wider than long, somewhat oval shaped. In females the eyes diverge slightly at the lower end; deep facial foveae are present. In males, there are nonmetallic white or yellow integumental markings on the clypeus. Also in males, the mandible is a simple point with only a small protrusion on the dorsal margin. THORAX: Densely hairy, hiding widely spaced pits, widest between the tegula. WINGS: Three submarginal cells. Stigma about the same width as the prestigma; the margins of the stigma are parallel to each other. LEGS: In females, the hind basitarsus is significantly shorter than the hind tibia (about half the length). The scopal hairs on the tibia and basitarsus include long hairs, so that the overall appearance of the scopae is that they are loose. ABDOMEN: In females, the anterior (forward-facing) surface of T1 has a small depression, and the dorsal surface of T1 is elongated. SIMILAR GENERA: Megandrena are similar to Andrena and Ancylandrena. Major differences are in wing venation; in Andrena the stigma is broader than the prestigma, and the margins converge at either end. The hind basitarsus in Andrena is also longer—more than half the length of the hind tibia. In Ancylandrena the anterior face of T1 is a much larger concavity, while the dorsal surface of T1 is shortened. Of the three Andreninae, Megandrena males are the only ones with a very simple mandible.

— Megandrena enceliae SIZE:

Medium to large; 13–16 mm. March through early May. FLORAL HOSTS: Frequently seen on Larrea tridentata, so a presumed creosote specialist; has also been collected on Argemone. RANGE: Centered in the Mojave and Sonoran deserts of southern Nevada, California, and Arizona; a few records from more northern locations in California. NESTING: Ground nester. IDENTIFICATION: Larger fuzzy gray andrenid with light abdominal stripes on a black integument. HEAD: Slightly wider than long, with deep wide facial fovea in female. In females, mandible is simple, with one notable but modest subapical tooth. In males, yellow facial markings cover clypeus and extend into paraocular region beside compound PHENOLOGY:

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Megandrena  113

Black integument Face wider than long, with light grey hair with deep wide facial fovea

T2 has a strong apical hair band across it.

Megandrena enceliae (female)

Megandrena mentzeliae (female) Megandrena enceliae (female)

Unlike M. enceliae, the abdomen of M. mentzeliae tends to be red.

Yellow markings cover the clypeus and the paraocular region.

Mandible dark

eye. Mandible in males is dark. THORAX: Black integument with light moderately dense covering of gray hair. LEGS: In females, the long hairs on the foretarsi are all straight. ABDOMEN: In females, T1 appears polished, with little in the way of Megandrena enceliae sculpturing. And T2 has a (male) strong white apical hair band that runs continuously across the segment. In males, numerous features exist on the genitalia that are not elaborated on here. SIMILAR SPECIES: The other species, Megandrena mentzeliae, is smaller, only about 10 mm. In females the narrow mandible lacks any subapical tooth. On T1 of females there is fine but strong sculpturing that makes the segment look dull. In males, the mandible is light colored. In both males and females, the abdomen tends to have red on it; in males T1–T6 are completely red, while in females, the base of the abdomen is red, growing darker posteriorly.

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114  Andrenidae

PROTOXAEA — SUBFAMILY: Oxaeinae OVERVIEW: Robust, showy bees, most active early in the morning. Males cluster together at night in large aggregations; one observer noted 2,000 individuals. Females nest in the ground and close the burrow while they are inside it. Protoxaea gloriosa, the species found in North America, does not appear to be a specialist but does have some preference for Fabaceae, Zygophyllaceae, and Solanaceae. IN THE WORLD: There are three species in the genus Protoxaea. Only one is found north of the Mexican border. The other two species are found in southern Mexico. CLEPTOPARASITES: Triepeolus. IDENTIFICATION: Large bee. HEAD: Eyes converge slightly toward top of head. Ocelli are low on the face, just above the antennae. The clypeus protrudes from the face. There are two subantennal sutures. THORAX: Covered in thick, short, orange hair. WINGS: Dusky. Marginal cell is very long, and there is no stigma. ABDOMEN: Dorsally, there is very little hair on the abdomen; the exception is a thick band of light hair on T5. In females, there are stout hairs on the sides of the sterna that are scopal hairs. SIMILAR GENERA: Bees in the subfamily Oxaeinae are found mostly in Central and South America, but two genera are represented by a couple of species in North America: Protoxaea and Mesoxaea. To the sides of the abdomen, on T5 in females, and on T6 in males, there are long tufts of white hair in Mesoxaea; these are absent in Protoxaea. Caupolicana is similarly large and with orange hair, but the brilliant white stripes on that bee are distinctive, as are the higher placed ocelli. Svastra is another genus of large bees with reddish hair. In males, the long antennae of Svastra should distinguish the two. In addition, Svastra has a shorter marginal cell than Protoxaea.

— Protoxaea gloriosa SIZE: Large; 15–22 mm; females significantly larger than males. PHENOLOGY: Emerges in the late summer, following monsoonal rains of the desert Southwest. FLORAL HOSTS: Generalist, but most common on Fabaceae (Senna species especially), Zygophyllaceae (Kallstroemia species and Larrea tridentata), and Solanaceae (Solanum species). RANGE: Arizona, New Mexico, and Texas. NESTING: Nests in ground, in sandy soil with some gravel outcroppings, as deep as 8 feet. IDENTIFICATION: Large orange bee with green or red eyes (when living). There is some individual variation in the hair on this bee; some individuals are lighter, while some are more red. As there is only one species in North America, most characters are listed above. HEAD: In males, the clypeus is black, only just edged with red at its lower

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Calliopsis  115 Protoxaea gloriosa (male)

Marginal cell very long Protoxaea gloriosa (female)

Ocelli low on the face, just above the antennae

No stigma

Protoxaea gloriosa (male)

Legs bright red-orange

Eyes green or red when alive

margin. In females, the posterior margin of the vertex rounds gently toward the thorax, with no carina. LEGS: In males, mid and hind femur are bright rusty red. ABDOMEN: Hairs are light-colored yellow or tan. SIMILAR SPECIES: This is the only species in the genus Protoxaea found in North America. See similar genera above for individuals in other groups that might resemble it.

CALLIOPSIS

Protoxaea gloriosa (female)

Abdomen nearly hairless dorsally, except for a thick band of light hair on T5

— SUBFAMILY: Panurginae — TRIBE: Calliopsini OVERVIEW: Medium to small bees, often slightly shiny, seen from late spring through fall. Nest in the ground, usually in barren open soil, or in highly disturbed areas with hard-packed or frequently overturned soil. Usually found in nesting aggregations. Many Calliopsis are specialists, though some are narrow generalists. IDENTIFYING FEATURES: Petite bees, often with yellow or ivory markings on the legs, and especially the face, and most prominently in males. HEAD: The face is oval-shaped, wider

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116  Andrenidae

than long, and with a microscope the two subantennal sutures characteristic of Andrenidae are clearly visible, as there is little hair on the face. The compound eyes may appear light blue, green, or gray in living specimens. THORAX: Shiny, with light hair on the sides. WINGS: The tip of the marginal cell angles away from the edge of the wing margin. There are two submarginal cells. LEGS: Hind tibia in males is toothed. ABDOMEN: Light pale stripes of hair run across the apical edge of each tergal segment. In males, S6 extends as long lateral flaps that almost cover over the bottom edge of the tergites. Though hard to see unless the specimen is dead, this feature is unique to Calliopsis males. IN THE WORLD: In all, 86 species are known. They are exclusive to the Americas, with 68 in North America. In western North America there are 66 species. CLEPTOPARASITES: Holcopasites, Sphecodes. SIMILAR GENERA: Halictus, Andrena, Perdita appear similar. The wing venations of Halictus are distinctive and not seen in Calliopsis, and Halictus have three submarginal cells. Female Andrena have thick facial foveae that are not seen in Calliopsis; typically, Calliopsis have more yellow markings on the integument, especially near the leg joints, but some male Andrena have yellow faces. Perdita are smaller, and the marginal cell on their wing is much more truncate.

— Calliopsis subalpinus SIZE: Small; 5–8 mm. PHENOLOGY: February through August, but most common from May through June. FLORAL HOSTS: Specialist on globe mallow (Sphaeralcea). RANGE: Nevada through Colorado, West Texas to southern California, restricted to desert environments. NESTING: Ground nesting. IDENTIFICATION: Small shiny black bee seen in flowers of Sphaeralcea. HEAD: In females, there are yellow spots beside the clypeus, below the subantennal sutures. In Yellow spots on the side males, the clypeus is yellow of clypeus and below the antennae on the sides, and black in the center. The eyes appear green to blue in living specimens. The antennae are black at the base, fading to yellow at the tip. THORAX: In males, the thorax is dark brown to black. WINGS: The marginal cell is narrow, cut off at its end. In males there is a Calliopsis subalpina dark spot on the tip of the (female)

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Marginal cell narrow, truncated at the end

Abdomen red dorsally, brown/black ventrally

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Calliopsis  117 Wing tip with dark spot

forewing. LEGS: In the females the middle tibial spur has fine, close-together teeth. ABDOMEN: In females, T1–T5 are red on the top (dorsally), but brown on the sides, as are the sternal segments. Antennae black at the base, fading SIMILAR SPECIES: The red to yellow at the tip abdomen in females is not common and can separate this Calliopsis subalpina (male) species from most others.

Eyes appear blue-green in living specimens.

— Calliopsis puellae SIZE: Small; 7–8 mm. PHENOLOGY: March through June. FLORAL HOSTS: Specialist on Asteraceae, common on desert dandelion (Malacothrix). RANGE: California to Utah, southern Idaho south through Arizona. NESTING: In ground, sometimes gregariously. IDENTIFICATION: Often found as mating pairs because males reduce mate competition by prolonged copulation. HEAD: Black to dark brown with light gray hair on face. THORAX: In females, the scutum is shiny, with few punctations at the back. Black to dark brown, also with gray hair. WINGS: Clear, no dark spot at outer margin. ABDOMEN: Broad yellow bands run across each tergal segment. In males, there is no notch at the center of S6 (this cannot be seen without a Calliopsis puellae microscope).

Scutum is shiny, with few puncations. Marginal cell truncated, not as narrow as in C. subalpina

(female)

Yellow bands run across each abdominal segment.

Calliopsis puellae (male)

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No dark spot on the tip of the wing

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SIMILAR SPECIES: Calliopsis obscurella looks similar but is much rarer. It differs in that the male has a peculiarly shaped central process on S6 and a light clypeus and narrower yellow bands on the abdomen.

MACROTERA — SUBFAMILY: Panurginae — TRIBE: Panurgini OVERVIEW: Small bees with relatively big heads, often black with a red abdomen, seen from early spring into the fall. Nest in the ground, with some species forming communal nests (many females sharing the same nest entrance while provisioning their own nest cells. Unlike many other bees, male Macrotera spend more time in the nest, even staying inside overnight on occasion. Most Macrotera are specialists, with some species showing a preference for globe mallow, while others specialize on cactus. IDENTIFYING FEATURES: Petite bees with heads that are broader than long (especially the males). HEAD: Well-developed facial fovea. The mandible has a groove running its full length. THORAX: Episternal groove is absent, or very short. The scutum and other parts of the thorax are never metallic, and there are few yellow spots. WINGS: Marginal cell is large, at least as big as the first submarginal cell, and dramatically clipped at the end. There are usually two submarginal cells. The stigma is slender, barely as broad as the pterostigma. LEGS: Males have flattened hairs on the metatibia and basitarsus. Tibial spurs are stout and hooked at the tip in both sexes. ABDOMEN: In males, the abdomen is flattened and broader than the thorax. IN THE WORLD: There are 31 species worldwide, all found either in the southwestern U.S. or northern Mexico, with 23 north of Mexico. CLEPTOPARASITES: Neopasites. SIMILAR GENERA: Perdita is very similar to Macrotera, and they were once considered the same genus. Macrotera have a groove on the outer surface of the mandibles that is unique, and not present in any Perdita species. Smaller Calliopsis may be similar to larger Macrotera. Calliopsis has a much longer marginal cell, and the hind tibia in males is toothed.

— Macrotera arcuata SIZE: Petite; 3–4 mm. PHENOLOGY: April through July. FLORAL HOSTS: Globe mallow (Sphaeralcea sp.). RANGE: Arizona into southern Utah, west through southern Nevada and California. NESTING: Ground nester. IDENTIFICATION: Very small bee, usually seen on globe mallow. HEAD: In both sexes, head is broad, much broader than long. The color of the head is black with greenish hue with erect finely

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Macrotera  119 Marginal cell is extremely truncate. Abdomen brown/black Macrotera arcuata (male)

Yellow clypeus

Thorax black with greenish hue, with erect finely branched white hair

branched white hairs. In males, the mandibles are simple, with only one tooth (compare with any other Macrotera). THORAX: Black with greenish hue, with erect finely Macrotera arcuata branched white hair. Abdomen black (female) ABDOMEN: Black or dark brown, or dark brown (not red like some other without red. In females, there is a species) pale area at the center of S6 that it is two to three times as long as it is wide. SIMILAR SPECIES: Females are most similar to M. echinocacti and M. latior. In both of those species, the central pale area on S6 is five to six times as long as it is wide. In males, M. arcuata has a simple mandible consisting of one pointy tooth.

— Macrotera latior SIZE: Petite; 3–4 mm. PHENOLOGY: May through October. FLORAL HOSTS: globe mallow (Sphaeralcea sp.). RANGE: Utah and Nevada, south into Mexico. Most prevalent in hot desert regions. NESTING: Ground nester. IDENTIFICATION: Very small bee, slightly bluish, usually seen in flowers of globe mallow. HEAD: Black with bluish hue with erect finely branched white hair. In males, there is yellow on labrum and clypeus. THORAX: Black with bluish hue with erect finely branched white hair. ABDOMEN: In females, the abdomen is dark black to brown. In males, it is red. In females, S6 has a clear/pale area that is significantly (5–6 times) longer than it is wide. SIMILAR SPECIES: Female M. latior are nearly indistinguishable from M. echinocacti, which is a specialist on cactus. If males are also seen, they can be used to distinguish the two. In males, M. echinocacti lack the point that extends off the sides of S2, as in M. latior. In addition, the male has less yellow on the clypeus—it rarely reaches the upper margin of the clypeus laterally as it does in M. echinocacti, where the yellow extends up to the inner margin of the eyes.

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Head and thorax bluish

Dark head and thorax with a bluish hue

Macrotera latior (female)

Red abdomen

Macrotera latior (male)

Dark brown/black abdomen

It appears that many species of Macrotera bet-hedge, so that only a fraction of bees emerge from the nest in a given year; others remain in the ground, in diapause. This appears to be an adaptation to the unpredictable nature of floral resources in desert environments.

— Macrotera portalis SIZE: Petite; 4.5–5 mm. PHENOLOGY: May through October. FLORAL HOSTS: Globe mallow (Sphaeralcea sp.). RANGE: Arizona, New Mexico, and Texas. NESTING: Ground nester, often communally with many females sharing the same area, or even the same nest entrance. IDENTIFICATION: Very small bee. HEAD: In females, the head is dark green, covered in relatively thick white hair. In males the head is mainly brick red, and the mandibles are large, scimitarlike, but with two tiny teeth at the apex. In both sexes, the head surface is roughened with minute punctures. THORAX: Black at the center of the scutum and scutellum, green around edges. Though not heavily polished, the scutum is slightly shiny, showing through the relatively thick white hair. WINGS: Milky white. ABDOMEN: In males, the abdomen is a red-brown color.

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Head and thorax dark green covered with thick white hair

the

Macrotera portalis (female)

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Panurginus  121

Males of this bee come in two forms: small-headed males, which emerge from the nest and fly to flowers in search of females with which to mate, and big-headed males, which are flightless. They stay underground in nests where females are provisioning, and mate with the females as they construct nest cells. They often fight with other big-headed males, using their enlarged mandibles, often to the death.

Mandibles are large, scimitarlike, with 2 small teeth at the apex. Macrotera portalis (male)

SIMILAR SPECIES: The red head in males and the milky wings are two distinct traits in this bee.

PANURGINUS — SUBFAMILY: Panurginae — TRIBE: Panurgini OVERVIEW: Small shiny black bees with a little yellow on the clypeus and legs of males. North American species include both specialists and generalists. Nest in large aggregations and sometimes communally, with several solitary females sharing a nest entrance, but building their own cells inside. Nests are always in the ground. IDENTIFYING FEATURES: Small, inconspicuous, black, nearly hairless bees. HEAD: Slightly wider than long, flattened across the vertex, and with the inner margins of the eyes very slightly converging toward the clypeus. In females, the facial foveae (indentations beside each compound eye) are hairless. In males, the clypeus is often bright yellow. THORAX: On the side of the body, there is no episternal groove. On the posterior end of the propodeum there are very tiny hairs on the sides. WINGS: There are only two submarginal cells. In Panurginus the first transverse cubital vein meets the second recurrent vein, making a “+” on the wing. LEGS: In both sexes, there are no yellow markings. ABDOMEN: In males, the margins of T2–T5 have at least some hair. IN THE WORLD: Panurginus is the only member of its tribe in the Americas. While Europe has more than 30 species, there are just 18 in North America, with the vast majority (17) in western states and provinces. CLEPTOPARASITES: Holcopasites. SIMILAR GENERA: Pseudopanurgus and Panurginus appear very similar to each other. The wing venation can be telling. In Panurginus, the first transverse cubital vein meets the first recurrent vein; it does not in Pseudopanurgus. Darker specimens of Perdita look similar to Pseudopanurgus, and both fly later in the year. The extremely truncate marginal cell in Perdita should distinguish the two. Hylaeus may also appear similar. The thorax of Hylaeus individuals is thinner between the tegulae, and the location where yellow markings occur is notably different between the two genera. Also, the face of Hylaeus is tapered, looking more triangular, as opposed to the wider, more rectangular face of Panurginus.

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— Panurginus gracilis SIZE: Small; 5–7 mm. PHENOLOGY: Early spring, February through April. FLORAL HOSTS: California lilacs (Ceanothus). RANGE: Southern and central California and northern Baja California, south into Mexico. NESTING: Unknown for this species, but likely a ground nester. In other Panurginus, ground nests are often large aggregations that are reused for more than 20 years. IDENTIFICATION: Small dark bee, longer bodied. HEAD: In both males and females, the head is all black, even the Head and antennae clypeus. The flagellar all black segments are all black. In females, the face has light hair, with perhaps a small amount of dark hair around the clypeus. In males, the apical edge of the clypeus has a deep notch at the center. THORAX: In males, Panurginus gracilis (female) the scutum has three strong raised ridges with one right down the center. Tegulae Three strong raised shiny black. WINGS: Clear ridges on the scutum wings. Stigma dark brown. Two submarginal cells. LEGS: All dark with no light markings. ABDOMEN: Slender and dark with no hair bands.

No hair bands on the abdomen

Legs all dark

Panurginus gracilis (male)

Panurginus gracilis (female) Panurginus gracilis (female)

First transverse cubital vein meets the second recurrent vein in a perfect “+”

Panurginus gracilis (male)

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n

Perdita  123

SIMILAR SPECIES: Females are very difficult to distinguish, unless accompanied by a male. Male P. gracilis is very distinct from all other Panurginus with its broad shallow clypeus with a notch in the center, and the raised lines on the scutum.

PERDITA — SUBFAMILY: Panurginae — TRIBE: Panurgini OVERVIEW: Extremely small metallic dull green or black bees often with yellow markings on the face and abdomen, seen most commonly in the late summer and fall. Nest in the ground, occasionally in large aggregations, but nests can be hard to see because the bee is so tiny. Many species are specialists, especially on fall composites (Asteraceae). Collect pollen with a significant amount of nectar, creating a muddy pellet instead of the more typical dry pollen seen in many other bees. Incredibly common in the West, especially in the later summer and fall. IDENTIFYING FEATURES: Petite, almost flat bees. Most species have extensive yellow or ivory integumental markings on the legs, face (especially the clypeus), thorax, and abdomen. HEAD: On the face there are two subantennal sutures (as with all Andrenidae). Perdita have facial foveae that can be distinctive; the width, length, and color of the hair inside are important characters in species identification. THORAX: Typically a metallic olive green color, and not solid black (though in the West entirely yellow species also exist). The degree of polish on the scutum, or overall tessellation (how rough the surface is) can be useful for separating species. An episternal groove is present and curves backward toward the scrobal groove. WINGS: There are two submarginal cells, often separated by milky-white veins. The marginal cell ends abruptly and sits next to a very large stigma. LEGS: In females, scopal hairs are sparse and seem almost nonexistent. ABDOMEN: In dead specimens, the abdomen is flattened, almost paper thin. On T2, there are often indentations on the side—foveae—that can help with species identification. Also, the shape of the pygidial plate differs between species. IN THE WORLD: More than 600 species in the world, all in the Americas. Most of them occur in North America, with close to 550 species in the western U.S.; only a very few occur north of the U.S. border. CLEPTOPARASITES: Neolarra, occasionally Sphecodes. SIMILAR GENERA: Similar in size to some Lasioglossum, especially L. (Dialictus). Lasioglossum (Dialictus) do not have yellow markings on their bodies, and are rounder than Perdita. If viewed up close, the three submarginal cells and tapering marginal cell of Lasioglossum can also distinguish the two. Pseudopanurgus and Panurginus are in the same family as Perdita and may superficially resemble Perdita. Though both can have yellow on the legs and thorax, Perdita often have a green-tinged integument, which does not occur in Pseudopanurgus or Panurginus. Perdita marginal cells are much more truncated than either Pseudopanurgus or Panurginus. Also, Panurginus are spring bees, and seldom overlap in flight season with Perdita. Hylaeus are also small with yellow

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markings; they are matte black, however, and the markings on their faces, and their face shapes, are very different.

— Perdita bellula SIZE: Petite; 2.5–3 mm. PHENOLOGY: April through October, but most common in summer in association with monsoonal rains. FLORAL HOSTS: Specialist on Boraginaceae, with a very strong preference for the genus Tiquilia. Their host plants typically don’t open until midday, and the bee is seldom seen before then. RANGE: Mojave and Sonoran deserts, common along roadsides. NESTING: Likely a ground nester in sandy soils. IDENTIFICATION: Small yellow bee, often seen on tiny flowers in the Borage family. HEAD: In both sexes, the eyes converge toward the bottom of the head. Clypeus and adjacent areas are pale yellow. Two dots appear on the sides of the clypeus. Yellow clypeus with two dots on the sides Moderately dense hairs run up beside the compound eyes. In females (as with all bees in the subgenus Heteroperdita) there is a “pollen-basket” on the underside of the head, with hooked hairs that Perdita bellula Light yellow abdomen curl toward the center. (female) with lateral spots on T1–T5 In males, the head is wider than it is long and has a slight bluish tint. THORAX: Light metallic blue, with matted white hairs, especially on the sides. There is no yellow triangle on the propodeum. WINGS: On the third row of cells, the medial cell, which is the outermost one in most bees, is absent, or only very lightly visible. LEGS: In females (as Perdita bellula (male) with all Heteroperdita), there are thick flattened hairs on the outer face of the midtibiae that face backward. ABDOMEN: In both sexes, the abdomen is straw colored with darker Head wider than Abdomen amber spots laterally on T1–T5. In long with a slight with some bluish tint light patches some forms, the terga are

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Perdita  125

darker, and the spots are not as evident. The abdomen is about the same width as the thorax. In females, the pygidial plate is rounded at its tip, rather than pointed, and parallel-sided. In males, the tergal segments tend to be a darker amber color, with few lighter patches. The pygidial plate is more angled, with a narrowly rounded tip. SIMILAR SPECIES: Perdita bellula is among the most common Heteroperdita, but also has some of the most variable color patterns. With 22 species in the subgenus, it can grade into some of the other species if looking only at color patterns. The wing venation, converging eyes, and shape of the pygidial plate can help separate when color patterns are too much like other species.

— Perdita aridella SIZE: Petite; 3–4 mm. PHENOLOGY: June through August. FLORAL HOSTS: Specialist on flowers in the Asteraceae, especially summer species (Grindelia, Chrysothamnus, Helianthus, Ericameria, Gutierrezia). RANGE: Utah and northern Arizona. NESTING: Presumably ground nesting. IDENTIFICATION: Small bee with metallic green head and thorax, and brown and yellow markings on the abdomen. HEAD: Dark green, round. In males, the clypeus, the gena, and the paraocular and supraclypeal areas are bright yellow. In females, the clypeus and the paraocular areas are yellow, but there are two dark lines extending into the clypeus. Also in females,

Head and thorax metallic blue-green; dull with no polish and sparse white hairs Tergal segments with broad yellow bands

Clypeus and paraocular areas are yellow, with two dark lines extending into the clypeus.

Perdita aridella (female)

Perdita aridella (male)

The clypeus, the gena, and the paraocular and supraclypeal areas are bright yellow.

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facial foveae are slender, oblong, very close to inner margins of compound eyes, and about the same color as the vertex. Mandible is simple. In both sexes, the scape is yellow, but in males the flagellar segments are also yellow, at least on the side facing out from the head. THORAX: Metallic green blue, very dull with no polish. White hairs are few and sparse, as are pits, which are tiny and widely spaced. Pronotal lobes are yellow, and in males the pronotal collar is as well. WINGS: Stigma large, but not as wide as the first submarginal cell. Veins are a light yellow color, and the wing is slightly milky. LEGS: Yellow in both sexes, but more brightly so in males, and with more brown areas in females. ABDOMEN: Yellow markings broad, and covering the center of each tergal segment, as well as the anterior surface of the first tergal segment. Brown outlines the yellow on each segment. In females, pygidial plate broad with a rounded tip. SIMILAR SPECIES: Most similar to the uncommon Perdita biparticeps. That species has a brassier undertone, clearer wings with pale veins, and a hairier thorax.

— Perdita beatula SIZE: Petite; 4–5 mm. PHENOLOGY: April through early July. FLORAL HOSTS: Specialist on Sphaeralcea (globe mallow). RANGE: Eastern side of the Sierra Nevada south to Arizona and north to Utah. NESTING: Presumed ground nester. IDENTIFICATION: A small, all-yellow species. HEAD: Round yellow head, slightly wider than thorax. Facial fovea are oval, light brown, about twice as long as wide. Antennae yellow. Mandibles simple. Gena about two-thirds the thickness of the compound eyes. Posterior simple eyes very close to the occipital margin. White hair is thick on the vertex and the frons. Perdita beatula (female)

Entire body, from the head to the tip of the abdomen, pale yellow

Perdita beatula (male)

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Perdita  127 THORAX: Yellow all over, though propodeum slightly tinged with green. Not shiny, but with tiny coarse pits. There is some thin white hair on the thorax. WINGS: Light white. LEGS: Yellow. Tarsal claws are split. ABDOMEN: Yellow. Small brownish dots on the sides of T2. Pygidial plate is as long as it is wide at the base, with a strongly notched apex. SIMILAR SPECIES: There are few species entirely yellow from head to abdomen tip, as this species is. Perdita xanthodes, though nearly all yellow, has a large black mark on the sides of the thorax, beneath the tegula, and the facial fovea are farther from the compound eyes.

— Perdita punctosignata SIZE: Petite; 3–5 mm. PHENOLOGY: April through early June, when mesquite blooms. FLORAL HOSTS: Specialist on Prosopis (mesquite). RANGE: Widespread in the Southwest, as far north as Nevada, Utah, and Colorado. East to Texas. NESTING: Likely nests in the ground. IDENTIFICATION: Very small yellow bee, appearing nearly hairless, seen swarming mesquite in the spring. HEAD: All yellow, and palest below the antennal sockets. At the vertex, a black line runs the width of the head— sometimes interrupted at the center. This line is more pronounced in males. In females, facial fovea deep black, oblong. In males, fovea is a small dark dot. Head round, as wide as long in Head yellow with females. Face is slightly deep black facial fovea roughened, but still shines. In females, mandible is one long, simple tooth. THORAX: All yellow. In females, below the tegula there is a black Perdita punctosignata mark running from top to (female) bottom. There may also be a black mark on either side of the scutum. In males,

Abdomen yellow with thin black bands at the base and apex of T2–T4

Black facial fovea is a small dot.

Perdita punctosignata (male)

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the propodeum may be black or yellow. WINGS: Stigma about as long and wide as first submarginal cell. ABDOMEN: Predominantly yellow, but with narrow brown bands at the base and apex of T2–T4, and the apical margin of T1. On T2, there are dark foveae on the sides. In females, the pygidial plate is broad, slightly longer than it is wide. SIMILAR SPECIES: There is substantial variation in this species across its geographic range. Perdita punctosignata punctosignata is the most widespread of the subspecies and is what is described above. The California subspecies (P. punctosignata sulphurea) has fewer dark marks on the head and thorax. Perdita punctosignata flava, which occurs along the U.S.-Mexico border in Arizona, New Mexico, and Texas, has a broader gena, and larger facial fovea. The dark markings on the head and thorax are also less noticeable in this subspecies. Other similar species, in the same subgroup, include P. stathamae. That species has heavier dark markings on the head and thorax, and females have an inner tooth on the mandible, which is simple in P. punctosignata. Perdita genalis also shares similar markings; it often has dark lines down the thorax, the gena is very thick, and the mandibles in females are not simple. Finally, Perdita discors is yellow, with markings as in P. punctosignata, but the face is longer than wide, and the clypeus is widened at its apex, so that it extends beyond the base of the mandibles.

— Perdita albonotata SIZE: Petite to small; 5–6 mm. PHENOLOGY: May through July. FLORAL HOSTS: Likely a specialist on Stephanomeria (wirelettuce). RANGE: Colorado Plateau south through the Mojave Desert. Some records in the Great Basin and as far north as southern Idaho. NESTING: Most likely a ground nester. IDENTIFICATION: Small lightly metallic green bee with extensive yellow markings on the face. HEAD: Vertex and frons dull, roughened slightly as if with sandpaper, but with a little polish evident beneath. Though hard to see, the maxillary palps are five-segmented. In females, light yellow marks run beside each eye up to the antennal sockets, drawing to a point on the inner margin. The sides of the clypeus are pale yellow, and there is sometimes a white line at the center as well. In males, the clypeus is pale yellow, with small brown dots to the sides of center. In addition, the paraocular area, the supraclypeal area, and areas below the antennal sockets are yellow. THORAX: Scutum metallic blue, with thin white hairs standing erect over surface. Pronotal collar with a rounded lobe at the edges. The pronotal lobe may be white or may be dark. LEGS: In females, scopal hairs are long, dense, and corkscrew-shaped. In males, the hind tarsal claws are simple. Also in males, the hind tibia has a small lobe at its apex, just above the tibial spurs. This can be hard to see without a microscope. ABDOMEN: In females, broad, light yellow bands run across the base of each segment, curving down toward

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Perdita  129

the apex on the sides. The apex is slightly transparent. In females, the pygidial plate is narrow and ends abruptly, with no notch in the middle. In males, T7 is rounded across its apex, with no sharp points. There are no broad stripes running across the tergal segments in males, just light yellow markings on the sides of T2–T5, with some light markings at the center of T4–T6. SIMILAR SPECIES: There are two other species in the same subgenus: Perdita moabensis has a duller frons and vertex, and more limited facial markings in females; in contrast Perdita stephanomeriae is very polished on the vertex (it also has three-segmented maxillary palps, but this is hard to see). In males, P. albonotata looks most like P. stephanomeriae, but in P. stephanomeriae the hind tarsal claw is bidentate (split), instead of simple.

Perdita albonotata (female) Vertex and frons dull, roughened slightly

Milky-white wings

Broad light yellow bands run across the base of T2–T5. Perdita albonotata (male)

There are no broad stripes running across the tergal segments in males, just light yellow markings on the sides of T2–T5, with some light markings at the center of T4–T6.

— Perdita rhois SIZE: Petite;

3–4 mm. PHENOLOGY: May through August. FLORAL HOSTS: Floral generalist. and central California. NESTING: Likely a ground nester. IDENTIFICATION: Very common bee in southern California. HEAD: Dark green. In females, clypeus, mandibles, and paraocular area are dark yellow and face is round, about as long as it is wide. Also in females, mandible tapers smoothly and has a small inner tooth. Facial foveae are long and narrow, and relatively close to inner margin of compound eye. In males, yellow is brighter and covers the face to just above the facial foveae. The gena are also yellow and wider than the width of the compound eye. Overall, in males, the face is wider than long. THORAX: Dark gunmetal green, slightly RANGE: Southern

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Clypeus, mandibles, and paraocular area dark yellow Perdita rhois (female)

Face mostly yellow extending to just above the facial foveae

Perdita rhois (male)

Yellow band on T2 does not extend to the edges of the segment.

This bee is purported to be the one that first sparked Charles Michener’s interest in bees; Dr. Michener is one of the world’s most important bee biologists, having given names to nearly 600 bee species.

roughened, with yellow pronotal collar. Some white hair is present, but it is short and sparse. In males, the ventral half of the body is also yellow. WINGS: Stigma large, slightly wider than first submarginal cell. Marginal cell short, and strongly angled away from wing margin. ABDOMEN: In females, predominantly brown, not metallic. Yellow bands occur basally on T2–T5; the band on T2 covers only the center of the segment, while those on T3–T5 extend to the edges. In females, pygidial plate is round at its apex, and not pointed. In males, brown bands extend across the apex of each yellow tergal segment. SIMILAR SPECIES: The large stigma and strongly angled marginal cell are distinctive, as is its generalist flower preferences. One other very common bee has these features: P. dasylirii. In P. dasylirii the legs of females are almost entirely yellow, but the yellow marks on the abdomen are more reduced.

— Perdita zebrata SIZE: Petite to small; 4–7 mm. PHENOLOGY: June through August. FLORAL HOSTS: Specialist on Rocky Mountain bee plant and yellow spider flower (Cleome sp.). RANGE: Common in Rocky Mountain states, New Mexico, north to Montana. NESTING: Ground nesting. IDENTIFICATION: Very common and abundant blue-green Perdita. HEAD: In females, yellow mandible is simple and tapers to small red point. On the frons and around the vertex, there are very few pits. The area just above the clypeus is yellow, and there are yellow marks beside the clypeus, running up to just below the narrow facial fovea. In

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Blue-green polished thorax with sparse pale hairs

Perdita zebrata (male)

Distinct brown spot on the posterior surface of the front and hind femurs Area just above the clypeus is yellow, and there are yellow marks beside the clypeus, running up to just below the narrow facial fovea.

Yellow mandible tapering to a small red point Perdita zebrata (female)

Abdomen mostly yellow with brown bands running across each segment

males, the area below the simple eyes is very rough, with a few distinct pits, and is overall dull. Also in males, yellow markings are similar to female, but include more yellow just above the clypeus. THORAX: Blue green, with sparse, pale hairs. There are few pits on the scutum. The pronotal collar and the pronotal lobe are yellow. WINGS: Stigma is long and narrow, about as wide as first submarginal cell. LEGS: Mostly yellow. In males, there is a distinct brown spot on the posterior surface of the front and hind femurs. ABDOMEN: In females, mostly yellow, with brown bands running across the apex of T1, and the bases and apices of T2–T4. At the sides, the brown bleeds down the sides of the segment. On T1, there are dark spots on the anterior face, to either side of the center. In males, T5 and T6 are mostly yellow. The first tergal segment is almost entirely brown. And T2–T4 are brown at the base, apex, and on the sides, nearly enclosing a yellow central area. SIMILAR SPECIES: Appears very similar to Perdita albipennis, but it is slightly smaller. Perdita zebrata has two subspecies: P. zebrata flavens has a brighter yellow abdomen, and more light areas on the head, thorax, and legs. Perdita zebrata zebrata is described above.

— Perdita fallugiae SIZE: Petite to small; 3–6 mm. PHENOLOGY: May through early July. FLORAL HOSTS: Specialist on Fallugia (Apache plume). RANGE: Western states, concentrated in Nevada, Arizona, Utah, and Colorado. NESTING: Presumed ground nester.

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IDENTIFICATION: Small dark bee, common on Apache plume. HEAD: Dark metallic green. The head is nearly round, or slightly wider than long in males. In females, clypeus and mandibles almost black, with large deep pits. Between the clypeus and the compound eye are two ivory-colored areas. In males, the clypeus and an extensive bit of the area between the clypeus and the compound eye are yellow. THORAX: Metallic green with widely scattered shallow pits. Short erect hairs are evenly distributed over the surface. The interspaces somewhat polished. Pronotal collar is the same color as the thorax. LEGS: Dark, with longer pale white hairs. ABDOMEN: Brown, polished, with sparse hairs. In females, T2 may or may not have a yellow mark on the side. Also in females, on T3 there is a longer comma-shaped mark to either side of center, while T4 is similar, but the yellow is smaller. In males, abdomen is mostly dark as well, but yellow stripes run across the center of each sternal segment. Also in males, on T2 there are two small yellow spots, one to either side of the center. SIMILAR SPECIES: Similar in appearance to P. cowaniae, with the differences in males in the genitalia. In females, the scutum is greener than in P. fallugiae, and the yellow coloring on the abdomen is broader, especially across T2, though it is still interrupted at the center. Abdomen brown with yellow mark on the side of T3 and T4

Perdita fallugiae (female)

Head dark metallic green with two ivory-colored areas between the clypeus and the compound eye

Perdita fallugiae (male)

Clypeus and area between clypeus and compound eye pale yellow Abdomen mostly dark with two yellow spots on the sides of T2

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— Perdita minima SIZE: Minute, the smallest bee in North America; 2 mm. PHENOLOGY: June through September. FLORAL HOSTS: Specialist on Euphorbia and Chamaesyce species (spurges and sandmats). RANGE: Arizona, California, and New Mexico. NESTING: Presumably a ground nester. IDENTIFICATION: Minuscule red gnatlike bee found crawling over the surface of tiny mat-flat flowers in the hottest part of the summer. HEAD: Rusty red to orange, including the antennae. Even the ocelli are a shade of red. In females, facial foveae are small oval brown spots. Head is round, or slightly wider than long in males. THORAX: Rust red to orange, with wide distinct pits on a semipolished surface. Pronotal collar and tegulae slightly darker than color of scutum. WINGS: Stigma large, nearly engulfing marginal cell. Second submarginal cell small to nonexistent. Propodeum darker brown. LEGS: Rust red with white erect hairs. ABDOMEN: Rusty red, with no yellow. Polished with few pits. Pygidial plate long, narrow, but not pointed at its apex. SIMILAR SPECIES: There are no bees that match Perdita minima in size and color. A few species of Perdita are rust red, including P. crandalli, but it is nearly twice the size, much less common, and does not appear to specialize on Euphorbia.

Stigma large, nearly engulfing marginal cell

Perdita minima (female)

Perdita minima (female)

actual size

Entire body yellow-orange

Perdita minima (male)

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— Perdita chamaesarachae SIZE: Petite; 3–4 mm. PHENOLOGY: June through August. FLORAL HOSTS: Appears to specialize on Chamaesaracha (five eyes). RANGE: Mainly restricted to the Chihuahuan Desert; New Mexico and Texas. NESTING: Likely a ground nester. IDENTIFICATION: Small dark bee with a red abdomen; distinctive on the white flowers of Chamaesaracha. HEAD: Polished dark green, but with white on the mandibles, the clypeus, and the area beside the clypeus, in a triangle leading up to the level of the antennal sockets. On the clypeus there are often two dark dots to either side of center. The head is round, only slightly wider than it is long. Mandibles taper to a sharp, red-tipped point. Males are slightly bluer, and the entire lower half of the face is white, including most of the scape. THORAX: Polished dark green, with a much bluer propodeum. Pronotal collar is white. Thin white hair stands sparsely erect on scutum and other structures. WINGS: Stigma large, nearly as wide as first submarginal cell. LEGS: In females, brown, with some yellow areas on apex of front and middle femur. In males, front and middle legs are nearly all yellow. ABDOMEN: Rust red. In females, pygidial plate is wide, with a notch at the apex. SIMILAR SPECIES: Perdita chamaesarachae is a member of the Halictoides group of Perdita, all of which look fairly similar. Only two have extensive white markings on the face as P. chamaesarachae does. In both those species (P. lenis and P. physalidis) there are lines on the clypeus, instead of dots. In males, P. lenis has a head that is wider than it is long, rather than round as in P. chamaesarachae. In P. physalidis, the head is slightly longer than wide, and there are more dark areas on the face, especially above the clypeus.

White clypeus and areas next to the clypeus Orange/red abdomen

Perdita chamaesarachae (male)

Perdita chamaesarachae (female)

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Perdita  135

— Perdita nevadensis SIZE: Petite; 3.5–4 mm. PHENOLOGY: June through August. FLORAL HOSTS: Unknown, may be a specialist on Eriogonum. RANGE: Pacific states and provinces. NESTING: Likely nests in the ground. IDENTIFICATION: Very small dark bee seen in summer months; patterning is highly variable and there are several subspecies. HEAD: Dark green, appearing almost black, polished, and wider than it is long. In females, the clypeus is yellow with two brown stripes to either side of center, as are the mandible bases and the area between the clypeus and the compound eye. In some individuals there is yellow just above the clypeus as well. In males, yellow is more extensive, covering all areas below antennal sockets. In females the head is slightly wider than it is long, but in males, it is Thorax dark green and polished much wider than long. In females, the facial foveae are deep impressions that run from the antennal sockets up the side of the face until just below the first ocellus. THORAX: Dark green, Perdita nevadensis very polished. Some thin white (female) hair is present. LEGS: Legs are dark, with some yellow marks. In females the yellow is on the fore femur and tibia. In males, yellow is more scattered with spots on the apex of the femur and tibiae of all leg pairs. ABDOMEN: Very dark, almost black. In both males and females, small yellow spots or commas occur on the sides of T1–T4. These are variable and may be more or less obvious depending on the individual. SIMILAR SPECIES: Females resemble Perdita affinis; the lateral marks on the face are cut off at their ends, with a notch, rather than terminating in a point as they do in females of P. nevadensis. Perdita nevadensis also looks like

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Abdomen dark with yellow comma-shaped marks on the sides of T1–T4

Yellow marks on abdomen are variable.

Perdita nevadensis (male)

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P. fallax; in that species, the face markings, as well as those on the abdomen, are almost white, as opposed to the yellow of P. nevadensis.

— Perdita nasuta SIZE: Petite; 2–3.5 mm. PHENOLOGY: May through July. FLORAL HOSTS: Specialist on Eriogonum sp. (buckwheat). RANGE: Texas west to the Mojave Desert in California. North to Utah and Colorado. NESTING: Presumably ground nester. IDENTIFICATION: Incredibly small but uniquelooking bee on buckwheat. HEAD: In females, the head is mostly polished light metallic blue. The face is wider than it is long. The clypeus is yellow, convex, and wider than its height. The mandibles are also yellow. In males, the entire face below the ocelli is yellow. The scape is inflated, only slightly longer than wide, and the other flagellar segments are all shortened, so that the antennae barely reach the back of the head. In males the clypeus is modified, with the lower margin sticking out so far from the head as to appear beaklike. THORAX: Dark bluish green, shining. Some white sparse hair present on scutum and areas around it. WINGS: Stigma long, and about as wide as the width of the first submarginal cell. LEGS: Legs are entirely yellow. ABDOMEN: Completely sherbet orange, with few pits, so that it is also polished.

Perdita nasuta (female) Orange abdomen Clypeus and mandibles yellow

Very small bee that specializes on buckwheat flowers

Face entirely yellow below the ocelli

Legs entirely yellow

Perdita nasuta (male)

Clypeus modified with lower margin sticking out from the face

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Perdita  137

SIMILAR SPECIES: No other Perdita in North America has a clypeus shaped quite like this one. Perdita nasuta males are therefore easy to distinguish. With females, the all-yellow legs and orange abdomen are unique, separating it from, especially, Perdita xerophila, which has darker legs, especially the femur. In addition, P. xerophila is larger, and the head is not especially wider than it is high.

— Perdita albipennis SIZE: Small; 6–7 mm. PHENOLOGY: June through September. FLORAL HOSTS: Appears to specialize on Asteraceae, especially sunflowers (Helianthus). RANGE: Midwestern and Rocky Mountain species. Alberta, Canada, south to Mexico, west to Nevada, east to southern Ontario, Wisconsin, and Mississippi. NESTING: Likely a ground nester. IDENTIFICATION: Very common and widespread dark Perdita, typically seen on sunflowers in the summer. HEAD: Dark metallic green. Slightly longer than wide, but with eyes converging because the vertex is a little wide. Clypeus polished, protuberant, appearing striped with light yellow with dark lines to either side of center. To either side of the clypeus there is a yellow mark, but this does not extend above the level of the top of the clypeus. In females, the facial foveae are deep and distinct, long and narrow. In males, the gena is wider than the compound eye. Unlike in many other male Perdita, the face is mostly dark with only a little yellow on Head and thorax dark metallic green the sides of the clypeus and Wings milky white beside the compound eyes. In both sexes, the hair on the head is relatively (for a Perdita) thick, dense, and white. THORAX: Dark metallic green, relatively

Perdita albipennis (female)

Perdita albipennis (male)

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densely covered in white hair. WINGS: Milky white, with white veins and a light-colored stigma. LEGS: Almost entirely brown, with light yellow spots on front and midtibiae. ABDOMEN: Dark brown black, variable; some with yellow blotches on T2 and T3, just to either side of center. In females, some have yellow on T4 and T5 that runs completely across the segment, between the apex and base. SIMILAR SPECIES: The smaller P. tricincta appears very similar to P. albipennis. Perdita tricincta is rare and found only in eastern and southern Texas. Perdita scopata is also similar, but is a brassier green and, in females, has a black clypeus with just one pale yellow line. Perdita coreopsidis is similar as well but is slightly smaller and also a brassier green.

— Perdita interrupta SIZE: Petite to small; 4–5 mm. PHENOLOGY: April through May. FLORAL HOSTS: Specialist on Eschscholzia (California poppies) but may also be seen on Cryptantha. RANGE: Central and southern California, maybe into western Arizona. NESTING: Presumed ground nester. IDENTIFICATION: Tiny dark bee with light stripes on the abdomen, usually seen rummaging in California poppies. HEAD: Deep metallic blue green, wider than it is long (more so in males), and relatively hairy. Base of mandibles, clypeus, labrum, and areas beside clypeus ivory white; those marks beside clypeus are triangular in shape and climb up to the height of the antennal socket. In males, the tips of the mandibles are red. Along the top margin of the clypeus there are dark marks to either side of center, sometimes as dots, but sometimes as stripes. In males, antennae are slightly ivory underneath; in females, they are usually light brown. THORAX: Deep metallic Perdita interrupta (female) blue green, with no yellow markings. Scutum roughened, with fine, widely spaced T1 has light spots on pits, when viewed up close, but the lateral margins. T2–T5 have light bands that are interrupted at the center.

T1 has a blue-green tint similar to the thorax.

Perdita interrupta (male)

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Perdita  139

appearing shiny from a distance. LEGS: In males, there are white spots on the femurs and on the anterior face of the front and midtibiae. Females are similar, but hind femurs are dark, and midfemurs have less yellow than males. ABDOMEN: Black, with T1 slightly tinted blue green. The second through fifth tergal segments have ivory bands, interrupted at the center, and T1 has an ivory spot on the lateral margins. SIMILAR SPECIES: There are three subspecies of P. interrupta that differ mainly in the amount of yellow on the face, and the amount of polish on the face and scutum. Perdita micheneri is similar but flies later in the year, visits Ceanothus and Rhamnus, and has less hair on the face.

— Perdita coreopsidis SIZE: Small; 5–6 mm. PHENOLOGY: May through July. FLORAL HOSTS: Specialist on Gaillardia (blanket flower). RANGE: Widespread in central western states and the Midwest. NESTING: Most likely in the ground. IDENTIFICATION: Larger metallic gold-green Perdita seen commonly on blanket flower. HEAD: Shiny metallic gold green, slightly wider than long, and coated with abundant short pale hairs. Clypeus all yellow, as are the areas between the clypeus and the compound eyes, and the base of the mandibles. Antennal scapes are yellow on the anterior side, with areas of yellow on flagellomeres as well; in males, most of the antennae is yellow. The glossa (tongue) is long, extending back to the front coxae. THORAX: Gold green, with yellow on the tegulae and pronotal collar. Stout white hair covers the polished surface, which has deep, distinct pits. WINGS: Very pale white. LEGS: Anterior face of femur is yellow. ABDOMEN: Predominantly yellow. In females there are brown markings at base of T2–T5. Also on females, on T1 there is a thick brown line just before the apex that extends across most of the surface. Stout light hairs cover the thorax. Perdita coreopsidis (male)

Head and thorax metallic green with a gold hue

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Abdomen mainly yellow/orange; thick brown line on sides of T2 Yellow tegulae

Perdita coreopsidis (female)

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In some individuals, the brown markings are faint or absent. In males, the brown markings are less, sometimes appearing only centrally on T1, and as brown dots on the sides of T2. SIMILAR SPECIES: There are four subspecies of P. coreopsidis, which differ in the amount of yellow on the abdomen and hind legs. Perdita coreopsidis kansensis has a mostly dark abdomen, with just four small lighter spots on T1 and two spots on T2. Perdita coreopsidis obscurior also has a mostly dark abdomen, with the yellow looking more like stripes, rather than vice versa. A few species are as large as P. coreopsidis, and as brightly colored (e.g., Perdita lepachidis), but few have the (typically) yellow abdomen, and the long glossa.

— Perdita similis SIZE: Petite; 3–4 mm. PHENOLOGY: Fall; August through October. FLORAL HOSTS: Specialist on fall composites, including Ericameria, Isocoma, and Chrysothamnus. RANGE: New Mexico north to Idaho, Wyoming, Washington, and Oregon. NESTING: Presumably a ground nester. IDENTIFICATION: Very small but common bee, often seen in swarms over fall composites. HEAD: Yellow green, broader than long, and with slender mandibles. In females, the clypeus, supraclypeal area, and areas between clypeus and compound eye bright yellow. In males, the entire lower half of the face is yellow. The frons and vertex appear shiny, Perdita similis (female)

Clypeus, supraclypeal area, and areas between clypeus and compound eye yellow

Lower half of face is yellow.

Perdita similis (male)

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Protandrena  141

with some small sparse punctures. THORAX: Yellow green with yellow pronotum, and yellow tegulae (especially at base). Males are slightly darker blue green, with yellow on the scutellum and the sides of the thorax. Some thin white hair occurs on the polished scutum, which has small widely spaced pits. Anterior to the scutellum, at the posterior edge of the scutum, there is a dense band of white appressed hairs. WINGS: Clear to slightly milky, with yellow veins. LEGS: Nearly all yellow; front coxae are green, and the hind tibiae are brown, except right at the base. ABDOMEN: Bright yellow, with dark bands running across each segment, sometimes appearing broad, because brown at the apex of one segment joins the band at the base of the next. In females, bands are broader at the junction of T1 and T2, but narrow at the junction of T4 and T5. In males, the base of T1 is dark. In females, pygidial plate is about as long as it is wide. SIMILAR SPECIES: Appears very similar, in terms of coloration, to the equally abundant Perdita proxima. Perdita proxima is bigger, though (4–5 mm), and has less distinct yellow markings on the supraclypeal area (in females). On the scutum, the pits are closer together in P. similis, and it has a denser band of appressed hairs right before the scutellum. May also appear similar to the less common P. oregonensis. That species has a much narrower head than P. similis, and in males the markings on the side of the face are broad, above the antennae.

PROTANDRENA — SUBFAMILY: Panurginae — TRIBE: Protandrenini OVERVIEW: Rarer, small slender bee, usually seen in late summer or fall. Many are specialists, usually on fall composites (Asteraceae). Nest in the ground, often in bare open soil. IN THE WORLD: There are roughly 180 species in the world, found throughout North, Central, and South America. There are several important subgenera with more restricted ranges (see below). In North America there are around 100 species. CLEPTOPARASITES: Holcopasites. IDENTIFYING FEATURES: Small dark bee, with very little hair and extensive yellow on the face of males. HEAD: The eyes are relatively parallel, and the face is slightly wider than long. In males, the lower half of the face is entirely yellow. As with all Andrenidae, two subantennal sutures are evident. THORAX: The scutum is matte black and parallel-sided. In some females there are yellow markings. In males yellow is usually limited to yellow spots on the pronotal collar. WINGS: May have two or three submarginal cells. LEGS: In females, scopal hairs are on the hind tibia and hind basitarsus and tend to be strongly feathered. Also in females, the midtibial spur is finely toothed (only visible under magnification). In males, there may be some yellow on the tibia. ABDOMEN: There are no hair bands or yellow markings. In males, T2–T5 have only very sparse hairs on the sides of each tergal segment, which may extend toward the center along the apical margin.

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Protandrena is a genus in transition. Historically, Protandrena was separate from the genus Pseudopanurgus; some of the subgenera of Pseudopanurgus have been elevated to genus level at different times, or have been moved back and forth between Protandrena and Pseudopanurgus (e.g., Heterosarus and Pterosarus). Currently, Protandrena is the broad umbrella that includes all Protandrena, Pseudopanurgus, and also the distinct subgenera of Pseudopanurgus. A review of publications may find the specific epithets associated with one or the other of these genera. In general, Pseudopanurgus has two submarginal cells, while Protandrena may have two or three. Pseudopanurgus has the anterior tentorial pit at the junction of the outer subantennal suture and the epistomal suture, or slightly lower. And, though hard to see, in both sexes the episternal groove on the side of the thorax is long, extending below the scrobal groove that runs beside it. Often, Pseudopanurgus do not have hair on the propodeal triangle, while Protandrena more often do, at least on the sides. Protandrena tend to be less robust and less coarsely punctate. The marginal cell is gently angled off the wing margin in most Pseudopanurgus, but is more truncate in Protandrena. SIMILAR GENERA: Hylaeus looks remarkably similar, but female Hylaeus have no scopae and have longer faces, usually with white or yellow markings on the face and legs, and eyes that converge toward each other.

— Protandrena mexicanorum SIZE: Small; 6–8 mm. PHENOLOGY: May through August. FLORAL HOSTS: Generalist, but frequent buzz-pollinator of Solanaceae (especially Solanum, nightshade). Also common on Kallstroemia species (Arizona poppy, or caltrop). RANGE: West Texas through New Mexico and Arizona, occasionally seen in Colorado. NESTING: Ground nester, often in dense aggregations. IDENTIFICATION: Large dark summer species, with distinct white band across lower third of face. HEAD: In both sexes, the markings on the face are off-white, running below the antennae from one compound eye to the other. In males, the mandibles, the labrum, and the antennal scape are completely dark. THORAX: On scutum, pits are deep and widely separated, all the way to the anterior margin.

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Protandrena mexicanorum (male)

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Protandrena  143 Three submarginal cells

Off-white markings below antennae

Protandrena mexicanorum (female)

The surface of the scutum is relatively shiny. Tegulae are white, as are the pronotal lobes. WINGS: Three submarginal cells. The marginal cell is truncated, ending abruptly. The wings have a slight red-brown hue. LEGS: In males, the legs are mostly dark. Also in males, the outer margins of the hind tibiae are strongly toothed. ABDOMEN: The pits are deep, and close together, except at the apex of each tergal segment, which is relatively smooth. On the base of the second through fourth tergal segments, there are bands of white hair. On the anterior-facing surface of T1, there are white hairs that stand up. SIMILAR SPECIES: Protandrena cockerelli is similarly large with a shiny scutum and evenly spaced pits; however, the pronotal lobes are entirely dark, as are the tegula. The two species co-occur in Texas and New Mexico, but P. cockerelli occurs farther east.

— Protandrena innuptus SIZE: Small; 7–8 mm. PHENOLOGY: June through September. FLORAL HOSTS: Generalist, collecting pollen from many summer-blooming plants. RANGE: New Mexico and Arizona north to southern Canada. Western Oregon and California east to Kansas and Missouri. NESTING: Ground nester. IDENTIFICATION: Fairly common black bee. HEAD: In females, face is entirely black. In males, clypeus and two half-circles on either side of clypeus are yellow. Flagellar segments on antennae are thick, wider than long. In both sexes, labrum is black. Vertex with thin white short hair that sticks straight up. THORAX: Shining, with coarse widely spaced punctation. Tegulae are red brown. No yellow spots on the pronotal collar or anywhere else. Scutum with thin white short hair that sticks straight up. WINGS: Two submarginal cells. Veins dark red brown. First recurrent vein meets the bottom of the

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Two submarginal cells on the wing

Body entirely dark brown black

Protandrena innuptus (female)

Two submarginal cells No yellow spots on pronotal collar

second submarginal cell near first submarginal cell. LEGS: Yellow on some joints, but otherwise brown. ABDOMEN: The first tergal segment is strongly pitted but also slightly polished. All segments are slightly darker at base than Clypeus and areas next at apex, so that apical margin to the clypeus yellow Protandrena innuptus appears as a light brown band. (male) SIMILAR SPECIES: Similar to Protandrena irregularis. Differences in wing venation, detailed in descriptions for the two species here, are the most distinguishing feature. Variations in punctation can help to differentiate; P. innuptus is more strongly pitted.

— Protandrena irregularis SIZE: Small; 6–7 mm. PHENOLOGY: June through early September. FLORAL HOSTS: Unknown, but may specialize on fall Asteraceae, including Grindelia (gumweed), Helianthus (sunflowers), and Thelesperma (greenthread). RANGE: Oregon and southern California east to Nebraska, Colorado, Utah, north to southern Canada and northern Montana. NESTING: Likely a ground nester. IDENTIFICATION: Petite dark bee, with some yellow on various parts of the body. Not common, but can be locally abundant. HEAD: In females, face completely dark. In males, face yellow below the level of the antennae, including labrum. Yellow may also extend beside compound eyes up past the antennae. Also in males, antennal scape yellow underneath. THORAX: Scutum with small weak punctures that are widely separated. The back (posterior) face of the propodeum is rough, with distinct

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Protandrena  145 Front tibiae are dark.

Face completely dark

Protandrena irregularis (female)

Scopal hairs thin, short, and not feathered

Scape yellow underneath

punctures. Thin dull white yellow below hair covers the surface of the Face the antennae thorax. Pronotal lobes are black. The tegulae are red brown. WINGS: Two submarginal cells. Wings Protandrena irregularis dusky colored. Second (male) submarginal cell much shorter than first, with first recurrent vein right about at its center. LEGS: In females, foretibiae are all black. Front tarsi are expanded, with a thin fringe of feathery hair on the back side. Also in females, the scopal hairs are thin, short, and not feathered. ABDOMEN: Thin, especially narrow in males, with fine punctures. SIMILAR SPECIES: See similar species under Protandrena innuptus.

— Protandrena aethiops SIZE: Small

to medium; 8–11 mm. through September. FLORAL HOSTS: Prefers late-summer and fall Asteraceae, especially Helianthus (sunflowers) and Verbesina (crownbeard). RANGE: Midwestern states west to Utah, Idaho, and eastern Arizona. NESTING: Ground-nesting species, often gregariously. IDENTIFICATION: Dark bee with dark wings, seen on fall composites in the Midwest. HEAD: Shiny, with deep, distinct, crowded punctation. In females, face is all black. Basal edge of the clypeus is slightly concave, with two almost teeth at lateral corners. In males, all areas below the antennal sockets are bold yellow. The anterior face of the antennal scape is also yellow. THORAX: Dark, with no yellow. Tegulae are also dark. PHENOLOGY: July

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146  Andrenidae

Heavily pitted, but on a polished surface. WINGS: Very dark, almost Protandrena aethiops (female) black, and long, seeming nearly to cover the abdomen. LEGS: In females, legs are entirely dark with orange hair, especially on widely spaced scopal hairs. Legs dark with In males, tibiae, femur, and orange hair tarsal segments are all Dark, heavily pitted thorax with a polished surface yellow. ABDOMEN: All black, appearing relatively large compared with thorax. The apex of each segment is without pits, and polished, especially near the center. The basal two-thirds of each segment are densely pitted. In females, T5 and T6 have bristly orange hair. SIMILAR SPECIES: This is Protandrena aethiops Apex of each tergite a very late flying bee, which (female) polished without pits can help distinguish it from other Protandrena. Overall, Protandrena aethiops (male) the body surfaces are more polished than other Protandrena. Legs in males are all yellow, and females have rather distinctive Face below orange hair on hind antennae yellow legs especially. On the legs, the tibia, femur, and tarsal segments are yellow.

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MELITTIDAE

Protandrena  147

Melittidae is a small group of bees, common, though often overlooked. In all areas of the world where melittids occur, they are rare and usually geographically restricted (though they may be locally numerous). Most bees in the family Melittidae are specialists, usually narrowly so, and a few have switched to collecting oils in addition to pollens from flowering plants. All species nest in the ground and may nest in small aggregations. There are no cleptoparasitic bees in the Melittidae. Melittidae is thought to be one of the oldest bee families. The group includes more than 200 species around the world. Most melittids are found in Africa, but a handful of genera have made their way to Europe, Asia, and North America. Worldwide there are 16 genera; in North America three genera can be found (see taxonomy section below for details). Several of these genera are common and speciose in the desert Southwest. IDENTIFICATION: At the family level, Melittidae are difficult to unite. Overall, the body form is similar to Andrenidae or Colletidae, but the features seen on Melittidae bee specimens are a mix of things normally associated with either short- or long-tongued bees, but not both. Moreover, the characteristics that separate this group from other bee families are on the tongue and genitalia, two regions notoriously difficult to see in bees that are not pinned, and even then, they may need to be dissected. If identifying the bee family is the goal, going through the process of eliminating other families and subfamilies may be an effective strategy (scopal hairs on abdomen or not, one or two subantennal sutures, shape of important wing veins, etc.). HEAD: Short-tongued bees, with all labial palpi short, instead of the last ones long. The glossa is shortened and pointed. THORAX: There is no episternal groove. LEGS: In the field, it may be noticed that the pollen load on the leg is slightly wet, instead of dry as in many bees. Scopal hairs are typically on the hind tibia. ABDOMEN: In Hesperapis, appears especially flattened in dead specimens of several of the All labial palpi common North American genera. are about the same length. Melitta tend to be more solidly built, and Macropis are chunkiest, with a rounded abdomen. The glossa is short, and not TAXONOMY: Three subfamilies occur forked or otherwise modified. in the world: Dasypodainae includes eight genera, but only one, Hesperapis, occurs in North America. The Melittinae comprises Macropis and Melitta in North America; two other genera occur, both in Africa. One of those African genera is Rediviva, where the front legs of female bees are longer than the length of the entire body. They are inserted into narrow corollas of Diascia to sop up floral oils at its base. A third subfamily, Meganomiinae, can be found in xeric habitats in Africa; there are four genera in this subfamily.

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148  Melittidae

HESPERAPIS — SUBFAMILY: Dasypodainae — TRIBE: Hesperapini OVERVIEW: Medium-sized gray bees with disheveled-looking scopal hairs, and striped abdomens. Many are specialists on plants in various families. Nest in the ground, often in sparse aggregations. IN THE WORLD: There are more than 24 species in seven subgenera in North America; an additional dozen occur in southern Africa (these may be a separate genus). CLEPTOPARASITES: Perhaps Townsendiella. IDENTIFYING FEATURES: Medium-sized, slight bee with relatively hairy brown or gray body. Interestingly, when pinning specimens of Hesperapis, the integument of the thorax feels extra soft, and pins go through easier than in other bees. HEAD: The clypeus and the rest of the head are entirely dark, with no yellow The first crossvein makes a markings. Though hard to see, there are right angle with the bottom vein, and ends close to the many features on the mouthparts that first recurrent vein. distinguish species. For all Hesperapis, the paraglossa has no hair on it. Though hard to see, the glossa has no hair on it. WINGS: Very transparent. Two submarginal cells, with the first longer than the second. The vein separating the first and second submarginal cells is at In Hesperapis, the right angles to the vein that defines their second submarginal cell is shorter than bottom edge. LEGS: Basitibial plate is large, the first. oval-shaped, and present in both males and females. ABDOMEN: Often polished, and with sparse to thick apical hair bands. In profile appears extraordinarily flattened. SIMILAR GENERA: Colletes, Andrena, and Halictus may look superficially similar, but all three have three submarginal cells, while Hesperapis have only two. Oddly, it does not look overly similar to other genera in the Melittidae bee family.

— Hesperapis larreae SIZE: Small; 6–9 mm. PHENOLOGY: April through July—most common in spring. FLORAL HOSTS: Possibly a specialist on Larrea tridentata (creosote bush). RANGE: Southeastern California through to Texas, north to southern Utah and the Mojave Desert in Nevada. NESTING: Ground nester on gently sloping sandy sites, at the base of clumpy plants. Not generally in dense aggregations. IDENTIFICATION: Small gray bee, with sparse soft hair. HEAD: The maxillary galea in both sexes is

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Hesperapis  149 Hesperapis larreae striated (very hard to see). Head (female) dark, with long white hair, Long white hair on the face except on except on clypeus. The head is the clypeus slightly wider than long, and the inner margins of the compound eyes converge slightly. THORAX: The thorax is black and polished, covered in short sparse pale hairs, and lightly pitted. The Midtibia has dense propodeum is hairless, and rounds silver-white hairs. gently to the sides, rather than being sharply angled. LEGS: In females, the midtibia has dense silver-white hairs, intermixed with dark thicker hairs. ABDOMEN: The tergal segments are shiny and dark, except for a reddish-brown lighter area just before the apical hair bands on T1 through T4, which are stronger at the sides than in the center. The pygidial Abdominal plate has a weak notch at its hair bands apex. weak in males Hesperapis larreae SIMILAR SPECIES: There is a (male) species of Hesperapis whose name is published only in a dissertation (Hesperapis timberlakei) that appears to be very similar to H. larreae, differing most notably in the flowers on which the bee is collected. This unpublished species appears to specialize on prairie clover (Dalea).

— Hesperapis laticeps SIZE: Small to medium; 6–11 mm. Males are as large as, or larger than females. PHENOLOGY: April through early June. FLORAL HOSTS: Specialist on Mentzelia (blazing star), and other plants in the Loasaceae plant family. RANGE: California, Nevada, and Arizona; restricted to the Mojave Desert. NESTING: Ground-nesting species. IDENTIFICATION: Small gray bee often seen on blazing star flowers. HEAD: Appears indented (concave) or very flat at its vertex.

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150  Melittidae

Abdomen reddish to black, with pale apical hair bands on T1–T5 Hesperapis laticeps (female)

Propodeum smooth with no pits

Hesperapis laticeps (male)

Head is dark, with long white hair on lower portions of face, and clypeus. Inner margins of compound eyes are nearly parallel. In males, the apical half of the mandible is shaped like a long blade. THORAX: Dark, shiny, with sparse short hairs. Propodeum smooth, with only very fine ridges, but no pits. Scutum long, longer than the distance between the tegulae. LEGS: Front tibia spined on the outer apical half with five or more short, thick, yellowish spines. ABDOMEN: Tergal segments are reddish to black, with pale apical hair bands on T1–T5. SIMILAR SPECIES: The indentation on the head, and the reddish abdomen are unique features on this bee (it is the only member of the subgenus Xeralictoides), as is the long bladelike mandible in males. There are two subspecies of H. laticeps: H. laticeps laticeps have darker abdomens, while H. laticeps rufiventris have redder abdomens.

— Hesperapis regularis SIZE: Medium; 10–13 mm. PHENOLOGY: May. FLORAL HOSTS: Specialist on Clarkia. RANGE: Restricted to foothills of central and southern California. NESTING: Ground nester, often in sparse aggregations. Males have been observed digging shallow burrows in which to sleep at night. Females back-fill their nest entrances with loose sand. IDENTIFICATION: Petite gray bees. HEAD: Dark, shiny, with white long but sparse hairs. The apical margin of the clypeus has a thin, translucent, light brown line. First flagellar segment at least one and a half times as long as the second flagellar segment. In females, the first flagellar segment is longer than the third one as well. Though hard to see, the

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Macropis  151

Hesperapis regularis (male)

First flagellar segment one and a half times as long as the second

maxillary galea is pointed, with the edges very straight. THORAX: Dark, shiny, covered in dense short white hair that is branched. The propodeal triangle is coarsely pitted, with pits so dense that they touch. LEGS: In females, the scopa on the hind basitarsus is divided at the back. Hesperapis regularis ABDOMEN: Polished, and all (female) dark, with short appressed hairs creating very distinct bands on the apex of each tergal segment. In females, the pygidial plate is flat, with a center area of appressed feathered hairs. SIMILAR SPECIES: Hesperapis fuchsi, H. semirudis, H. nitidula, H. pellucida, and H. wilmattae are all in the same subgenus (Panurgomia) and so appear similar in that they have a very long first flagellar segment, and a pygidial plate with flattened hairs at the center. Hesperapis regularis is by far the largest of these, and the only one with pointed galea.

MACROPIS — SUBFAMILY: Melittinae — TRIBE: Macropidini OVERVIEW: Dark, rather robust bee with longer hind legs, often with hair that strongly contrasts with that of the rest of the bee. These bees are closely associated with Lysimachia (loosestrife). The females collect oil from structures located at the base of the flower petals (near the stamen). They have interesting adaptations to help them

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152  Melittidae

The first recurrent vein ends relatively far from the first crossvein (compare to Hesperapis).

collect this oil, usually in the form of modified hairs on their legs. The oil is thought to be used both as part of the larval provision and as a waterproof coating for the cell walls in their nests, which are in the ground. IN THE WORLD: There are 16 species of Macropis in the world, restricted to the Northern Hemisphere. Four species occur in North In Macropis, there are America; only one makes it to western states and provinces. two equally sized submarginal cells. CLEPTOPARASITES: Epeoloides (not covered in this book). IDENTIFYING FEATURES: Stout, rarely seen dark bees. Only one species is found in the West. HEAD: Wider than long. In males, clypeus is yellow. THORAX: Broad; scutum is smooth with only very fine but deep punctures. WINGS: Two submarginal cells, with second as long as, or longer than the first. The vein separating the first and second submarginal cells is strongly angled off the vein forming the bottom of these cells. LEGS: Hind basitarsus is short and very wide with fine hairs covering it (for collecting floral oils). Scopal hairs, on the hind tibia, are entirely white. ABDOMEN: Very thin white bands run across each tergal segment; these can be quickly worn off. Pygidial plate is well developed in both males and females. SIMILAR GENERA: While the overall shape of Macropis is distinct, they look similar to some smaller members of the family Apidae. Most Apidae have three submarginal cells. Also, the close relationship of Macropis to loosestrife plants can aid in identification.

— Macropis nuda SIZE: Small; 7–8 mm. PHENOLOGY: June through September. FLORAL HOSTS: Specialist on loosestrife (Lysimachia) but may be seen nectaring on common forest plants: Geranium, Rubus, Vaccinium, and Apocynum. In addition to collecting pollen from loosestrife, M. nuda also collects floral oils from the petals, scraping them off with her forelegs, and storing them in her scopae. RANGE: Idaho east to New England, and across southern Canada. NESTING: Ground nester, often in loose aggregations, in moist soil. BEHAVIOR: Females are often seen with their hind legs extended and stretched above their abdomens. This appears to be a posture used to discourage males from trying to land and mate. IDENTIFICATION: Medium to small bee, mostly dark, but with bright white hair on mid and hind legs. HEAD: Clypeus, and other parts of the face, covered in wide deep distinct pits. Mandibles and labrum are black. In males, clypeus is all yellow. There are small dark spots between the clypeus and the eye. Also in males, the supraclypeal area has a narrow yellow mark. THORAX: Thin white hairs outline the dorsal surface of the thorax,

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Macropis  153

slightly redder near the scutum and scutellum. The pits are deep and widely separated, and easy to see through the thin hair. The propodeum is polished, with tiny shallow pits. LEGS: In females, legs are mostly dark but with white hair, with scopae on hind tibiae thick, and bright white. Hairs on the hind basitarsus are all black. The midtibiae also with white hair. In males, the mid basitarsus is slender, the same length as all the other tarsal segments combined, but the hind basitarsus is thick, not at all narrowed. Also in males, has two well-developed hind tibial spurs. ABDOMEN: The tergal segments are smooth and shiny. Thin white hair bands run across each tergal segment, often interrupted near the sides. In females, the pygidial plate is fringed by dense brown-gray hair. The scutum is wide, polished, and has fine SIMILAR SPECIES: There are four deep punctures. species of Macropis in the U.S. and Canada, only one of which occurs in western states. In the Midwest, a combination of two features can distinguish the four. In females, two species have pale hair on the hind Macropis nuda basitarsus. For these two, (female) M. ciliata has a propodeum that is completely polished Macropis are often and smooth, and M. patellata The hind basitarsus is wide in wonderfully buffed with very all Macropis. In this species rounded body parts and stout legs. has a rough propodeum, the hairs are black. Macropis nuda dull and not at all polished. (female) Two species have black hair on the hind basitarsus. Hair bands are For these two, M. nuda has not always very highly polished terga, while visible. M. steironematis has coarsely punctate tergal segments. The large hind basitarsus is Similarly in males, M. steironematis especially noticeable from the side. has close and deep pits on the Macropis nuda unpolished abdomen; the (male) other three species have Punctures on scutum are fine and spaced widely. small pits on a shiny surface. Macropis patellata

In most male Macropis the clypeus is yellow with a tiny bit of yellow beside the compound eye and above the clypeus. In M. nuda, some individuals have a black clypeus.

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Legs are covered with thin white hairs.

Two submarginal cells

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154  Melittidae

and M. steironematis both have one small hind tibial spur. Macropis nuda has two well-developed hind tibial spurs. M. ciliata males have both hind tibial spurs reduced.

MELITTA — SUBFAMILY: Melittinae — TRIBE: Melittini OVERVIEW: Melitta, though not well represented in the U.S. and Canada, are a notable component of the bee fauna of Europe and other areas in the Northern Hemisphere. Many Melitta are specialists, though the floral host choices are eclectic and include many plant families. Most are presumed to be ground nesters. IN THE WORLD: More than 50 species of Melitta can be found around the world; most occur in the Northern Hemisphere, but a few species occur in Africa. In North America there are four species. CLEPTOPARASITES: Stelis. IDENTIFYING FEATURES: Medium-sized gray and brown bee. HEAD: Dark, with no yellow on the clypeus. The labrum has a lobe on each side. Eyes are more or less parallel to each other, with no facial fovea beside the compound eyes. THORAX: Moderately hairy, especially on the anterior end of the scutum. The propodeal triangle is a large surface, lacking any polish. WINGS: Three submarginal cells, with second as long, or longer than the first. The vein separating the first and In Melitta, there are three submarginal cells; the second and third combined second submarginal cells is strongly angled off are about the same size as the first. the vein forming the bottom of these cells. LEGS: In females, the hind tibia and hind basitarsus are slender, and the scopal hairs are all simple. ABDOMEN: Robust, not flattened as in Hesperapis, and with thick hair. The first recurrent vein SIMILAR GENERA: Andrena, Halictus, and ends relatively far from the first Colletes all share a similar body shape to crossvein (compare to Hesperapis). Melitta, and distinguishing them can be difficult. Colletes have angular faces not seen in Melitta. Andrena have deep facial foveae next to each compound eye (in females) not seen in Melitta, and in Melitta, scopal hairs are restricted to hind tibia and basitarsus, while they are dense on the femur and coxa of Andrena. And Halictus have an arcuate basal vein that differs from the straight one seen in Melitta. Within the family Melittidae, Melitta is the only genus with three submarginal cells.

— Melitta californica SIZE: Medium; 11–14 mm. PHENOLOGY: April through July. FLORAL HOSTS: Specialist on globe mallow (Sphaeralcea). RANGE: California and Arizona; restricted to Mojave and Sonoran deserts. NESTING: Presumed ground nester.

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Melitta  155

Melitta californica (female)

Melitta are much fuzzier than Macropis; underneath the hair, the scutum isn’t as polished as it is in Macropis.

IDENTIFICATION: There are three submarginal cells; Relatively robust melittid, note that the middle one is square shaped, and not very narrow. similar in appearance to Andrena. HEAD: Wider Melitta californica than long, with a mix of (female) light and dark hair; dark hair especially obvious on the sides of the face, and on the vertex. In females, the mandible is shorter than the length of the compound eye. THORAX:  The basitarsus is narrower than in Melitta, and the scopal hairs are short and stiff. In males, the scutum has both light and dark hairs intermixed, though In males, antennae from a distance the denser are notably long. white hairs are much more apparent. LEGS: With mostly light hair. In females, there are pale yellow hairs on the inner surface of the hind tarsi. ABDOMEN: In females, The clypeus is not yellow T5 has white hairs, especially in males. Melitta californica laterally, with some dark hairs (male) found toward the center of the apex. Around the pygidial plate there are dark brown hairs. In males, the sixth sternal segment has three distinct tufts of hair, before the apex. Also in males, the rim of S6 is broadly rounded, with no indentations. SIMILAR SPECIES: There are four species of Melitta in the U.S. This is the only species that is found in the West.

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156  Megachilidae

MEGACHILIDAE

Megachilidae are incredibly morphologically diverse. From yellow and black to brilliant green, this group includes a rich array of color morphs, as well as of structural adaptations on the face and legs. Within the Megachilidae are generalists and specialists, with many preferring flowers in the mint (Lamiaceae), pea (Fabaceae), and figwort (Plantaginaceae) families. Though there are ground-nesting Megachilidae, a larger proportion of bees in this family nest in preexisting cavities: twigs, beetle burrows, snail shells, nail holes, and prefabricated bee hotels. Nests are constructed using many substrates and may include mud, sawdust, leaves, plant trichomes, petals, or small pebbles. Parasitic bees also occur in the Megachilidae, and many are very strikingly colored. The Megachilidae bee family includes the largest bee in the world, Megachile pluto, which lives on an island in Indonesia. In North America, famous species include the alfalfa leaf-cutter bee (Megachile rotundata) and the blue orchard bee (Osmia lignaria), both of which are used commercially for pollination. It also includes many commonly seen introduced species, such as the widespread European wool carder bee (Anthidium manicatum) and the giant resin bee (Megachile sculpturalis). IDENTIFICATION: Megachilidae are perhaps one of the easiest families to recognize without a microscope. Their bodies are robust, thick, and often cylindrical instead of the flattened or petite stature of some other bee families. Many genera have yellowand-black markings across their bodies. All female Megachilidae that are not parasitic carry pollen exclusively on the underside of their abdomens, a characteristic not found in any other bee family.* The pollen can often be seen bulging out from the sides of the abdomen, even when the abdomen is not directly visible. HEAD: Labrum (which is hinged to the clypeus) is big and hinged across its entire width, giving it a rectangular shape. Megachilidae are long-tongued bees. WINGS: Two submarginal cells, with the second being noticeably longer than the first. TAXONOMY: In North America there are more than 600 species of Megachilidae, in 18 genera, though this is less than one-quarter of the number found worldwide (more than 4,000 bees in nearly 80 genera). Megachilidae occur on every continent and are also well represented on islands (likely a result of the tendency of many species to nest in wood, which can float to islands). Probably for the same reason, many of the invasive species found in North America are in the Megachilidae. In the West, two subfamilies occur, one of which contains numerous tribes and the bulk of North America’s genera. * Other bee genera may carry some pollen on the underside of the abdomen but will also carry it on their legs.

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MEGACHILIDAE  157

—  SUBFAMILY LITHURGINAE There are two genera in this subfamily: Lithurgus (not included in this book— introduced from the Mediterranean; seen in the Northeast on Centaurea flowers) and Lithurgopsis. They can be distinguished from other Megachilidae by the numerous bumps and spines (sometimes called tubercles) on the outer surface of the tibia. Males possess a pygidial plate, and in females this structure is spinelike or at least elongated.

—  SUBFAMILY MEGACHILINAE Sixteen genera occur in this subfamily; all are found in the western U.S., though some are not common. None of these genera possess pygidial plates. A few have tubercles, as in Lithurginae, but in general, these are absent. The genera are divided into four tribes, which are relatively easy to tell apart. — ANTHIDIINI: Large group of robust, often yellow-and-black bees. In addition to color patterns, the cleft tarsal claws (or at least an inner tooth) are distinctive among Megachilinae. On the wing, the stigma is usually very short. And on the hind legs, there are often numerous simple bristles. Seven genera in North America, all occur in the West: Anthidiellum, Anthidium, Dianthidium, Paranthidium, Pseudoanthidium (one introduced, rare species, not included in this book), Stelis, and Trachusa.

Anthidium

Anthidiellum

Dianthidium

Paranthidium

Trachusa

Major characters that differ between genera of nonparasitic Anthidiini

Number of teeth, in females

5 or more

Fewer than 5

3

Fewer than 5

Fewer than 5

Subantennal suture shape

Straight

Long and curved outward

Straight

Straight

Straight

Preoccipital ridge

Rounded

Outlined by a strong carina, overhangs scutum

Rounded

Rounded

Rounded

Pronotal lobe

Rounded, one species lamellate

Rounded

Extended as paper-thin plate toward the head

Paper thin but very short

Rounded

Scutellum

More or less rounded

Swollen, shortened overhangs metanotum

More or less rounded

More or less rounded

More or less rounded

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158  Megachilidae

— DIOXYINI: This tribe includes just one genus in North America: Dioxys. It is a parasitic bee and can be recognized most evidently by the wasplike body with no scopal hairs, the slender mandibles, and the spine at the center of the metanotum. — MEGACHILINI: This tribe includes two genera in North America, Megachile and Coelioxys. Medium to large dark bees. Coelioxys is the parasite of Megachile. As a whole, the tribe can be distinguished from other Megachilidae by the dark body and the black-and-white stripes on the abdominal segments, and the lack of an arolium between the front claws. There are no yellow markings on these bees. — OSMIINI: In the West, this tribe includes eight genera of small to medium-sized bees, sometimes metallic, but often matte black: Ashmeadiella, Chelostoma, Heriades, Hoplitis, Osmia, Protosmia, Xeroheriades, and Atoposmia (the latter two are not included in this book). Between the tarsal claws is an arolium.

Protosmia

Ashmeadiella

Chelostoma

Heriades

Hoplitis

Osmia

Major characters that differ between genera of Osmiini

Parapsidal line

Long and linear

Long and linear

Long and linear

Long and linear

Long and linear

Shortened, dotlike

Clypeus

With median spoonlike projection

Variously shaped, no median projection

Variously shaped, no median projection

Variously shaped, no median projection

Rounded

Variously shaped, no median projection

T6 in males

Rounded

With 4 strong teeth

Rounded

Rounded

2 teeth, one on either side of center

Rounded

Scutum shape, tegula position

Rounded, tegulae on anterior half of scutum

Rounded, tegulae on anterior half of scutum

Very elongated, tegulae midway down scutum

Rounded, tegulae on anterior half of scutum

Rounded, tegulae on anterior half of scutum

Rounded, tegulae on anterior half of scutum

Abdomen shape

Rounded

Rounded

Elongated but does not curl notably

Elongated and often curled under in males

Rounded

Rounded

Body color

Black

Black, may have red abdomen

Black

Black

Metallic or black

Metallic or black

Anterior surface of T1

Slightly concave, no carina

Slightly concave, no carina

Flat

Concave, with carina

Flat

Slightly concave, no carina

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Ashmeadiella  159

ASHMEADIELLA — SUBFAMILY: Megachilinae — TRIBE: Osmiini OVERVIEW: Small compact black bees, typically seen in late spring and summer. Many are specialists, especially on Asteraceae, but generalists also occur. Nests are made in wood or stems, in burrows in the ground, or under rocks. These bees are occasional inhabitants of bee hotels. IN THE WORLD: Ashmeadiella occur only in the Americas, and there are 57 species ranging from Costa Rica north to southern Canada. About 50 species can be found north of the Mexican border; all but two are western species. CLEPTOPARASITES: Stelis. IDENTIFYING FEATURES: Small to medium-sized bees, usually matte black (never metallic), but occasionally with red on the abdomen, and with strong punctation throughout. The body segments are rounded, not flattened, giving a stocky appearance when viewed from the side. As with all Megachilidae, there are two submarginal cells. HEAD: Face is longer than wide, and also thick, often with a broad gena (cheek) behind the compound eyes. In males, the mandible is usually bidentate (subgenus Chilosmia is tridentate). In females, the mandible typically has three or four teeth, but some species have two (subgenus Cubitognatha), and some have five (a few species in subgenus Ashmeadiella). THORAX: There is a sharp edge separating the forward and lateral faces of the side of the thorax (the omaulus) in all but one subgenus (Isosmia). The parapsidal line is elongated. WINGS: Two submarginal cells. Large stigma. LEGS: There is an arolium. ABDOMEN: Thin white hair bands run across the apical margin of each tergal segment. The first tergal segment is concave but lacks a carina separating the dorsal and forward-facing surface. In many species, the abdomen is either all red, or has red segments. In females, pollen-collecting hairs are on the underside of the abdomen, and T6 has a translucent lip at its apex. Males have four teeth on T6, underneath which T7 is usually hidden; the subgenus Isosmia differs in that T6 is not toothed. Ashmeadiella, especially in the subgenus Ashmeadiella, may be difficult to differentiate. There is considerable variability in some species. See references for taxonomic keys to help with the nearly 20 species in that subgenus. SIMILAR GENERA: Chelostoma and Heriades are Osmiini with an overall similar appearance. The omaular carina in Ashmeadiella is distinctive. Additionally, the scutum of Chelostoma is significantly longer, and the abdomen of Heriades tends to curl under, a characteristic not seen in Ashmeadiella. Hoplitis and Atoposmia also appear similar. One key distinguishing feature, for males, is the size of S2 compared with S3; in Ashmeadiella they are roughly the same size. In Hoplitis and Atoposmia they clearly differ in size.

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160  Megachilidae

— Ashmeadiella bucconis SIZE: Small; 6–10 mm. PHENOLOGY: May through August. FLORAL HOSTS: Specialist on Asteraceae, with a preference for Helianthus. RANGE: Across the U.S. and as far north as southern Canada. More common in western states (Colorado and west) than in eastern states. NESTING: Nests in small hollow twigs, in which it creates nest partitions with masticated leaf material. IDENTIFICATION: Matte-black bee, large for an Ashmeadiella, with coarsely pitted integument, and little hair. HEAD: Large head, with well-developed gena and Narrow hair bands run vertex. Gena is as thick, or thicker than, the width of the compound across the apical margin of each tergal segment. eye. The ocelli are relatively close The distance from the ocelli to the together and shifted down on the vertex is greater than the distance from the ocelli to the compound eye. head; the lowest ocellus is closer to the antennal sockets than it is to the back of the head. In males, the mandible has two teeth. In females, the clypeus is relatively short, slightly protruding, and the lower margin is a straight, to slightly convex, line; there is an impunctate polished line along Scutum is marked its apex. Under the lower edge of the by deep, wide pits. Note the wide, Ashmeadiella clypeus, there are two orange brushes almost bulging gena. bucconis (female) of hair. THORAX: Scutum is covered in wide, deep punctation. LEGS: Entirely black to dark brown. Apex of the hind tibial spur is straight. ABDOMEN: Slightly elongated and with parallel sides. Each tergal segment is coarsely pitted and all In Ashmeadiella, the change between the lateral black. In males, on T6, the middle two and forward faces of the side of the thorax are teeth are short, and rounded, with a marked by a sharp edge, especially ventrally. small curved notch between them. Each segment has a thin but complete band of white hair.

Ashmeadiella bucconis (male)

Between the front claws of Ashmeadiella is an arolium.

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All male Ashmeadiella have teeth on T6; those of A. bucconis are particularly small.

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Ashmeadiella  161

SIMILAR SPECIES: There are two subspecies of A. bucconis. Ashmeadiella bucconis bucconis is more common in the East, while A. b. denticulata is the common western subspecies. In A. b. denticulata, the ocelli are not pushed as far forward on the face as they are in A. b. bucconis. In females, the scopal hairs are yellow/white in A. b. denticulata, and browner in A. b. bucconis. Where the two overlap, in Texas, New Mexico, and north to North Dakota, they can be difficult to distinguish as they grade into each other. Ashmeadiella bucconis looks similar to A. californica and A. cubiceps. Ashmeadiella cubiceps has a large circular notch in the center of the clypeus, which is missing in the other two. Ashmeadiella californica females have a distinct white hair band on T5, about as dense as the one on T4; A. bucconis does not. Male A. bucconis and A. occipitalis appear similar. A. occipitalis has a large, sparsely punctate area at the vertex that appears polished.

— Ashmeadiella gillettei SIZE: Small; 5–7 mm. PHENOLOGY: April through August. FLORAL HOSTS: Apparent generalist. RANGE: Widespread throughout the West, but absent from the Northwest. East to North Dakota and Nebraska. NESTING: Presumed twig nester. IDENTIFICATION: Small Ashmeadiella with little hair, often with some red on the abdomen. HEAD: Round head, with white hair covering most of the lower surface. Gena thinner than the width of the compound eye. Clypeus covered in coarse, dense pits. In females, the inner margins of the compound eyes converge slightly toward the clypeus (males do too, but not as much). The lateral margins of the clypeus are about as long as the central margin of the clypeus. The margin of the clypeus is dark in color. There are three teeth in the mandibles of females, and two

Ashmeadiella gillettei (female)

Abdomen usually red but may have some black areas.

Tegula red

Clypeus covered in coarse dense pits

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Ashmeadiella gillettei (female)

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162  Megachilidae Abdomen red with in males. THORAX: Tegulae are red. some black areas Scutum with deep dense pits that are close together; in males, pits are further apart. LEGS: The claws, hind femur, and parts of hind tibiae may be red. The outer hind tibial spur is straight to very slightly curved. ABDOMEN: Usually red but may be black, strongly pitted. When red, often with black areas. The first through fifth tergal segments with thin white hair bands. Ashmeadiella gillettei (male) These get thinner on T4 and T5. In males, T6 has broad lateral teeth, and wide central teeth with rounded tips. Between the two central teeth is a semicircular notch. In females, though difficult to see, S6 has a distinct depression running across it, which is more coarsely pitted than the rest of the sternal segments. SIMILAR SPECIES: This species is highly variable, and there appear to be several subspecies of A. gillettei that grade into each other and differ primarily in the amount of red on the abdomen. Ashmeadiella gillettei looks similar to A. holtii, which is much rarer. In females, the lateral margins of the clypeus are wider than the center in A. holtii, and the mandible is more than twice the length of the scape along its outer margin. In males there are three teeth on the mandible of A. holtii and two on the mandible of females.

— Ashmeadiella meliloti SIZE: Small; 6–8 mm. PHENOLOGY: March through June, some records from September and October suggesting a second emergence. FLORAL HOSTS: Generalist. RANGE: California and Oregon east to Texas, Montana, and Utah; concentrated in the southwestern U.S. NESTING: Presumed twig nester. IDENTIFICATION: Medium-sized black bee. HEAD: Round, with eyes not converging significantly. Gena is narrow, only about half the width of the compound eye. Ocelli positioned near vertex; the distance between the posterior ocelli is about the same as the distance to the back margin of the head. In females, the margin of the clypeus is slightly convex. THORAX: Tegulae are black, with few pits. Scutum coarsely punctured, but with shiny spaces in between punctures. LEGS: Dark, lacking any red. ABDOMEN: The tergal segments are strongly punctate. In males the middle two teeth on T6 are long. In females, T5 lacks a band of white hair.

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Ashmeadiella  163

Tegulae black with few pits Tergal segments strongly punctate

T5 lacking apical hair band

Ashmeadiella meliloti (female)

Ashmeadiella meliloti (female)

Gena narrow, about half the width of the compound eye Ashmeadiella meliloti (male)

Ashmeadiella meliloti (male)

Middle 2 teeth on T6 long

SIMILAR SPECIES: This species appears very similar to A. aridula, and they co-occur in many areas. The tegulae are brown in A. aridula, however, and the punctation on the scutum is much smaller and closer together. In females, the clypeus of A. meliloti is slightly more convex and bulges out slightly more than in A. aridula.

— Ashmeadiella opuntiae SIZE: Small

to medium; 8–11 mm. April through early July. FLORAL HOSTS: Specialist on Cactaceae. RANGE: Concentrated in the Southwest and the Great Basin, but north to Idaho, South Dakota, and east to Texas. NESTING: Presumed twig nester. IDENTIFICATION: Large robust Ashmeadiella, matte black with very little pubescence. HEAD: Ocelli are close together, slightly pushed forward on head, nearer to antennal sockets PHENOLOGY: Late

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164  Megachilidae Ocelli close together, closer to each other than they are to the back of the head or compound eye

Ashmeadiella opuntiae (female)

than to preoccipital ridge, Ashmeadiella opuntiae Hair band on (female) and posterior ocelli are closer T5 as dense as that on T4 to each other than they are to the back of the head or to compound eyes. Width of gena about the same as the width of the compound eye, White hair bands or slightly wider. On the on T1–T5 vertex, the punctation is dense, with pits very close together. In females, the clypeus is truncated, and Ashmeadiella opuntiae there are two small (male) projections where the central margin meets the lateral margins; T5 without apical the lateral margins are hair bands shorter than the central margin. Punctation on the clypeus is sparse and fine. LEGS: Entirely dark. ABDOMEN: Entirely dark. In females, white apical hair bands occur on T1–T5, with the band on T5 as dense as that on T4. In males, T5 lacks an apical hair band. Also in males, the central two teeth on T6 are longer than they are wide, and the lateral teeth are long and pointed. Though hard to see, in females, S6 is only weakly depressed, and does not have deep or distinct pits, as some other species do. SIMILAR SPECIES: Most similar to Ashmeadiella foveata, though that bee is slightly smaller. In A. foveata, the ocelli are more widely spaced, about the same distance from each other as they are to the compound eye. The clypeus is also more heavily pitted. In males, the long middle teeth on T6 of A. opuntiae are notable.

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Chelostoma  165

CHELOSTOMA — SUBFAMILY: Megachilinae — TRIBE: Osmiini OVERVIEW: Long-bodied bees, petite with cylindrical bodies. Bees are small, spring to summer fliers. Most appear to be specialists, but pollen preferences are unknown for many species. Chelostoma nest in cavities, usually small beetle burrows in trees, but may also nest in hollow twigs, nail holes, or other preexisting holes. IN THE WORLD: Chelostoma occur widely throughout the Northern Hemisphere, with more than 50 species. In North America there are 11 species, eight of which are found in western North America and Canada. Two are native to Europe and are relatively recent introductions to North America. CLEPTOPARASITES: Stelis. IDENTIFYING FEATURES: Small slender bee, matte black with only minimal white hair. HEAD: In females, the mandible can have two, three, or four teeth. THORAX: The distance between the tegulae is less than the length of the thorax; a line drawn between the anterior margins of the tegulae is in the posterior half of the scutum. This is in part because the scutum is shifted forward with relation to the bottom of the body, so that the whole body is elongated. The sides of the thorax run smoothly from the forward face to the sides. A long parapsidal line is visible. The propodeum is normally pitted, with no row of strong pits running across the posterior end. WINGS: Two submarginal cells. LEGS: There is an arolium between the tarsal claws, which are forked. ABDOMEN: T1 does not have a carina separating the anterior and dorsal faces. In males, T6 does not have four distinct teeth along the apical margin, though there may be teeth on T7. In females, pollen-collecting hairs are on the underside of the abdomen. SIMILAR GENERA: Hylaeus individuals are a similar color and size and also have long bodies, but Chelostoma lack the yellow markings so prevalent in Hylaeus. Ashmeadiella, Heriades, and Hoplitis are in the same tribe (Osmiini), so share a similar overall body shape. Of the four, Chelostoma exhibit the longest, narrowest thorax. Heriades and Hoplitis often have light hair bands on the abdomen, which are less common in North American Chelostoma. The abdomens of Heriades tend to curl under, while Chelostoma do not. Ashmeadiella males have teeth on T6 that characterize them, and both male and female Ashmeadiella have a strong carina separating fore and lateral faces of the side of the thorax.

— Chelostoma californicum SIZE: Small; 8–9 mm. PHENOLOGY: April through June. FLORAL HOSTS: Phacelia. RANGE: Concentrated in California but ranging rarely as far east as Utah and New Mexico. NESTING: Nests in holes in wood, and in plant stems. The walls between cells are made of mud or soil grains, stuck together with nectar or saliva. IDENTIFICATION: Largest and hairiest of the Chelostoma species in North America. HEAD: Round, about as long as it is wide, very hairy. Clypeus with fine close punctation;

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166  Megachilidae

in females the lower margin is straight, with no notches, though small bumps or teeth may be visible, with short hairs below. Mandible has three teeth. Though hard to see, the maxillary palps are threesegmented. THORAX: Fine, even punctation on dull surface of scutum, very little hair. The face of the propodeum that faces the abdomen is polished. The sides of the propodeum have sparse, varied pits. ABDOMEN: On T1–T4 there are thick white hair bands running along the apex of each segment, thicker along the sides, thinner at the center. Second sternal segment has a raised bump that runs laterally across the segment. In females, scopae are white. In males, T7 has three teeth, the middle one is pointed, but not acutely. SIMILAR SPECIES: This is the largest and hairiest Chelostoma species, which can help with distinguishing it from the other Chelostoma species.

Chelostoma californicum (female)

The propodeum is well polished.

Thorax has fine even punctation on a dull surface.

T1–T4 with white hair bands

Chelostoma californicum (male)

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Chelostoma californicum (male)

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Chelostoma  167

— Chelostoma phaceliae SIZE: Small; 5–6 mm. PHENOLOGY: May through July. FLORAL HOSTS: Specialist on Phacelia (scorpion weed). RANGE: Southern British Columbia south to the California-Mexico border. Pacific coast of California east to Utah. Absent from the west side of the Cascades. NESTING: Nests in holes in wood, and in plant stems. The walls between cells are made of mud or soil grains, stuck together with nectar or saliva. IDENTIFICATION: Very small black bee with few hairs. HEAD: Round, about as long as it is wide, or maybe slightly longer. Clypeus with widely spaced punctation. In females, the lower margin of the clypeus has slight waves or bumps, and long hairs below. Mandible has three teeth. Though hard to see, the maxillary palps are four-segmented, with the first one being short and round. Overall, the mouth parts are greatly elongated. The gena and underside of the head are hairier than the rest of the face. In females, the margin of the clypeus is straight across, between the tubercles. THORAX: Fine, even punctation on dull surface of scutum, very little hair. The face of the propodeum that faces the abdomen is roughened. WINGS: Large for body size, slightly dusky. ABDOMEN: There are no thick white hair bands running along the apex of each segment, just very narrow broken ones. Second sternal segment has a raised bump that runs laterally across the segment. In females, scopae are white. In males, T7 has three teeth; the middle one is long, and acutely pointed. SIMILAR SPECIES: Difficult to distinguish from other Chelostoma species in the field. Under a microscope, the four segments of the No thick white maxillary palps are unique. With three hair bands along apex of tergal Chelostoma phaceliae teeth, it is similar to C. bernardinum, segments (female) C. cockerelli, and C. minutum. Chelostoma bernardinum has a wavy Chelostoma phaceliae apical margin on the clypeus, with (male) long hairs underneath, like C. phaceliae. The pits on the sides of the propodeum are more uniform and denser than in C. phaceliae. Chelostoma cockerelli has a long mandible, nearly as long as the compound eye.

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168  Megachilidae

HERIADES — SUBFAMILY: Megachilinae — TRIBE: Osmiini OVERVIEW: Petite, cigar-shaped black bees, easily overlooked as they visit flowers in the summer. Include both generalist and specialist species. Nest in very small preexisting cavities, usually in wood (one western species reported in pine cones). Nest cells are usually separated from each other by resin. IN THE WORLD: Worldwide there are around 140 species, found in North America, Europe, Asia, and Africa. Eleven species occur in North America, 10 of which are found in western states and provinces. CLEPTOPARASITES: Stelis, Coelioxys. IDENTIFYING FEATURES: Small, rather long dark bee with thin white stripes of hair on the abdomen. HEAD: Appears slightly longer than wide and is often thick, with a deep gena. In males, the mandible has two teeth; in females, there are three. THORAX: The pits are large and deep, giving the bee a roughened appearance. There is a distinct row of square pits that makes up the dorsal surface of the propodeum. There is a distinct carina just posterior to these pits, separating the dorsal and posterior surfaces. WINGS: Two submarginal cells. LEGS: Arolium present. ABDOMEN: First tergal segment is concave, forming a deep cavity that is lined by a strong ridge. From above, each section of the abdomen appears to constrict at the apical end, giving the sides of the abdomen a wavy look. In females, pollen-collecting hairs are on the abdomen. Most distinctive, the abdomen curls under in males, forming a comma shape; this is especially evident in dead male specimens. The sixth tergal segment in males does not have teeth. SIMILAR GENERA: Some of the other small Osmiini look similar. Heriades has a concave face to the front of the first tergal segment that is missing from other Osmiini. Also, while Chelostoma has a long body like Heriades, the abdomen differs significantly between the two. The abdomen of Heriades constricts after each segment, while that of Chelostoma does not. The abdomen of Chelostoma also doesn’t curl under, nor does it have white stripes as predominantly across the abdomen. Hoplitis tends to be shinier and more polished and lacks the concave section on the first tergal segment. Small Megachile may look similar, but the waviness on the sides of the abdomen in Heriades should separate it. Also, Megachile lack an arolium, which is found in Heriades individuals.

— Heriades cressoni SIZE: Small; 5–6 mm. PHENOLOGY: July through September. FLORAL HOSTS: Generalist, often seen on Asteraceae where it appears to “drum” the flowers with its abdomen when collecting pollen. RANGE: British Columbia south to Baja, east to Colorado and New Mexico. Largely absent from the Great Basin. NESTING: Presumably in twigs. IDENTIFICATION: Small, nondescript elongated black bee. HEAD: Dark round head, with very little hair in females, but white thick hairs in males over the clypeus and supraclypeal area. The clypeus has fine, close punctures. In females, the clypeus is

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Heriades  169

broadly concave at the center, and the labrum has two rounded projections to either side of the center at its base. Also in females, on the mandible, there are two carinae that join together close to the mandible’s base. There is a short ridge on the mandible, just above where the two carinae meet. THORAX: Scutum close and densely pitted, with very little space between punctures. ABDOMEN: Shiny, with medium-sized pits that are more and more coarsely pitted from the anterior to posterior segments. Narrow bands of white hair line the apex of each tergal segment. In males, S1 has a long projection, like an inverted shark fin pointing toward the back of the body. SIMILAR SPECIES: Heriades cressoni resembles other Heriades that have similar mandibles. The most distinctive character is also the hardest to see: the two tubercles at the base of the labrum in H. cressoni are unique to this species. Heriades crucifera appears similar, if the labrum is overlooked, but has a longer vertex, so that the distance between the lateral ocelli is much smaller than the distance between them and the back of the head. The mandible of H. cressoni has a small ridge near where the other mandibular carinae join together. This small ridge is not visible in H. micheneri or H. variolosa, both of which are similar to H. cressoni in other aspects. Scutum densely pitted with very little space between punctures

Narrow bands of white hair at the apex of each tergal segment

Heriades cressoni (female)

Heriades cressoni (male)

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170  Megachilidae

HOPLITIS — SUBFAMILY: Megachilinae — TRIBE: Osmiini OVERVIEW: Black, medium-sized bees, often with a fuzzy thorax, seen in the spring. Typically found at higher elevations where other bees drop out, but plenty of lowelevation species occur too. Include generalists and specialists. Hoplitis nesting habits are diverse, with species nesting in preexisting cavities in wood, in twigs, in the ground, or even in external nests made of pebbles and mortar stuck to the surface of larger rocks. May nest in aggregations. IN THE WORLD: There are around 360 species around the world; the genus is most diverse in Europe and Asia, especially in xeric regions of southern Europe, northern Africa, and the Middle East. A few species occur as far south as Malaysia and southern Africa, but they are absent from Australia and South America. In North America there are around 60 species, with over 50 in the West. One North American species is introduced (Hoplitis anthocopoides). CLEPTOPARASITES: Stelis, Dioxys. IDENTIFYING FEATURES: Medium-sized shinier black bee (green species in the West) with modest white hairs on abdomen and thorax. HEAD: In males, the final segment of the antennae is hooked, or tapers to a very thin point. THORAX: Parapsidal lines are long lines, instead of small points. The scutum is wide, with the distance between the tegulae greater than the scutal length. WINGS: Two submarginal cells. Stigma longer than it is wide. LEGS: There is an arolium between the tarsal claws. ABDOMEN: The first tergal segment is flat, without a notable concavity. Short white hairs line each tergite. Pits on the abdomen are small and widely spaced. At the end, the abdomen tapers gently to a point, rather than abruptly ending. In females, pollen-collecting hairs are on the underside of the abdomen. In males, S6 has a pair of translucent, thin, hairless flaps that emerge from the base. These are unique to Hoplitis. Also in males, T6 usually has a small tooth at either side. Seven tergal segments are visible in males. Though these characters are hard to see in individuals on flowers, they are very distinctive. SIMILAR GENERA: Hoplitis look most similar to Osmia, and the most distinguishing feature is the parapsidal line, which is only a small dot in Osmia but a long line (more typical in bees) in Hoplitis. Heriades are similar in coloring and size to eastern Hoplitis, but the front of the abdomen is not concave in Hoplitis as it is in Heriades, and there are no strong punctations associated with the posterior edge of the propodeum in Hoplitis. Heriades are more common in the summer, while Hoplitis are earlier in the year. In general, Hoplitis can be difficult to distinguish from each other. We have included four species here that are commonly seen, but there are many other species in the West, and the differences between them are variable, and minute.

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Hoplitis  171

— Hoplitis albifrons SIZE: Small

to medium; 9–12 mm. through August. FLORAL HOSTS: Appears to have a strong preference for Phacelia. RANGE: Across North America; more common at higher elevations and latitudes, from Maine and Newfoundland west to Alaska and the Northwest Territories, south to Baja, Arizona, and Texas. NESTING: Twig-nesting species, apparently separates nest cells with macerated leaf material. IDENTIFICATION: Elongated larger bee; jet-black integument. HEAD: Face covered with long white hairs, especially on the frons and supraclypeal area. Some dark hairs may be mixed in, especially on the gena, and the vertex. The face is long, nearly twice as long as the distance between the compound eyes. The gena is wide, about twice the width of the eyes. In females, the mandibles have four teeth, while males have two. In males, the last antennal segment is pointed. Also in males, the hairs on the lower portion of the face are short and remarkably silvery. THORAX: Long intermixed white and black hairs appear on the scutum, scutellum, and the sides of the propodeum. ABDOMEN: The first tergal segment has thick white hair. Short dark hairs cover T2–T6, except for the apical margins, which are outlined by thick bands of white hair, especially on the sides of T2. In females, the hair bands are mostly on T2 and T3. Also in females, scopal hairs are all black. PHENOLOGY: May

Hoplitis albifrons (female) Elongated jet-black bee Thick white hair on first tergal segment, and apex of T2 and T3 Wide gena

Black scopal hairs

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172  Megachilidae

Hoplitis albifrons (male)

SIMILAR SPECIES: There are three subspecies of H. albifrons: H. a. albifrons, H. a. argentifrons, and H. a. maura; they differ mostly in where they occur and the amount of white hair on their bodies, and where subspecies co-occur they tend to grade into each other. Hoplitis albifrons albifrons is in the far north, occurring throughout Alaska, and south to northern Minnesota, Michigan, and Maine. In this subspecies, the hair on the face is mostly white, as is that on the scutum and scutellum. The second and third tergal segments have white hair bands. Hoplitis albifrons argentifrons occurs in the Pacific Northwest, the east side of the Sierra Nevada, and east to the Rockies. The hair in the middle of the face is more than half black, and on the scutum and scutellum there is a significant amount of black hair intermixed with the white. The second and third tergal segments have white hair bands. Hoplitis albifrons maura occurs in California, west of the Sierran divide, and usually below 5,000 feet. It is very dark, with hardly any white hairs on the body.

— Hoplitis biscutellae SIZE: Small

to medium; 9–13 mm. at lower elevations, as late as July at higher elevations. FLORAL HOSTS: Likely a specialist on Larrea tridentata (creosote bush). RANGE: Desertadapted; found in the Mojave, Sonoran, and Chihuahuan deserts of the Southwest. NESTING: The only Hoplitis in North America known to nest in the ground. Has been observed nesting in abandoned nests of the mud-dauber wasp. Appears to use resins from Larrea tridentata in nest construction. IDENTIFICATION: Large, robust bee, black with black legs and long pale hair. HEAD: In males, the mandible is bidentate, in females it is tridentate, and as wide at its apex as PHENOLOGY: April

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it is at its base. Also in males the last segment of the antenna is narrowed to a point, and all the flagellar segments appear somewhat flattened in profile. THORAX: Coarsely punctate scutum, surrounded by long thin white hairs, and some shorter denser hairs outlining the dorsal faces. WINGS: The wings are without hairs inside the cells, but with small hairs near the outer edge. LEGS: Legs are black, though the tarsal segments and tibiae may be red to orangish. ABDOMEN: In males, T7 has three teeth, though when the abdomen curls under these are hard to see. The tergal segments are pitted, with the surface in between not greatly polished. Just above the apical margin there is a thin band of white hair that runs the width. SIMILAR SPECIES: Hoplitis biscutellae looks similar to H. Hoplitis biscutellae paroselae but can be distinguished (female) by the red legs in the latter. And in males, the last tergal segment has Hoplitis biscutellae (male) three teeth in H. biscutellae, but one single point in H. paroselae. It may bear a passing resemblance also to H. hypocrita. In that species females have four teeth on their mandibles, males have thinner antennae, and in both sexes, the wings have hairs inside the cells.

— Hoplitis fulgida SIZE: Small

to medium; 7–11 mm. and May at lower elevations; June through August in mountainous regions (up to 10,000 feet). FLORAL HOSTS: Generalist. RANGE: Western species, occurring from the Rocky Mountains (as far south as their southern ranges) west to the Yukon. Typically found at higher elevations. NESTING: Nests in preexisting cavities in wood, or in woody stems, using plant material and pebbles to create partitions. IDENTIFICATION: Brilliant blue-green bee, elongated. HEAD: Brilliant green with fine dense punctation. Clypeus sticks out very slightly from PHENOLOGY: April

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the face. Vertex thick, as is the Hoplitis fulgida gena. In males, the mandibles (female) have two teeth; in females, there are four teeth. Females have dark short sparse hair on the face. Males have light hair on the face, though the clypeus has long black hairs that stand up. THORAX: The scutum is covered in dense fine pits, with a rough integument between. In males, hair on the thorax is white, while on females it is long, thin, and dark. WINGS: Slightly smoky. LEGS: Brilliant green. ABDOMEN: Brilliant green to blue, with dense fine punctation. On the apical margin of T2 through T6 Hoplitis fulgida (male) there are thin bands with no pits. In females, scopal hairs are black, thick, and often can be seen poking out the sides when the bee is viewed from above. In males, on S1 and S2 there is a spine at the center. On S3 and S4 there are shining elevated areas just to the side of center. SIMILAR SPECIES: No other Hoplitis in North America is brilliant green, as this bee is. It may appear more similar to species in the genus Osmia than to other Hoplitis. See similar genera above for identification tips between those two. There are two subspecies of H. fulgida; H. f. fulgida is found in all areas outside of California. It has very pale hair, and in males T7 is narrowed just before its apex, so that there is a minute hourglasslike projection at the end of the abdomen. Hoplitis fulgida platyura occurs in California and is absent from low-elevation desert regions there. In males, T7 is broad and evenly rounded. In females, the hair is slightly darker. Where the two overlap (northern California and southern Oregon), they grade into each other.

— Hoplitis producta SIZE: Small; 6–8 mm. PHENOLOGY: Mid-April through July. FLORAL HOSTS: Polylectic, visiting a wide array of flowering plants. RANGE: Widespread across the U.S. and southern Canada. NESTING: Solitary, nests in hollow stems, including elder, sumac, and rose.

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IDENTIFICATION: All-black small-sized bee, with white hair bands. HEAD: In females, the head is as long as wide. The clypeus has a distinct rim that flips out from the plane of the clypeus. At its center, the clypeus is gently concave, but not notched. In males, the antennae taper to a fine point that hooks slightly; the scape is thickened, and less than two times as long as it is broad. THORAX: Pits are deep, and distinct, but the space in between is shiny. ABDOMEN: Thick white hair bands run across all the tergal segments, though they are interrupted on T1–T3. The seventh tergal segment has a large projection in the center, shaped like a very narrow isosceles triangle. In males, on S2, there is a large, pointed projection, steeply angled on both sides. The hair bands on T1–T3 are all interrupted.

In females, the clypeus is gently curving, but not notched.

Hoplitis producta (female)

Hoplitis producta (male)

S2 has a strong, sharp projection on it.

The tips of the male antennae are flattened and very slightly curled. The tip of T7 is a triangular point.

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Projections to either side of T6

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SIMILAR SPECIES: Hoplitis producta is difficult to distinguish from other western Hoplitis in the same subgenus; they tend to grade into each other, and there is considerable variability in different specimens of the same species. Of all the related species, males generally have the most produced projection on S2. As an indication of their variability, there are six subspecies, mostly distinguishable by where in the country they occur.

OSMIA — SUBFAMILY: Megachilinae — TRIBE: Osmiini OVERVIEW: Often boldly metallic-colored, easy-to-see bees that fly mostly in the early spring (many overwinter as adults, needing little time to complete development when temperatures warm in the spring). Range from solid black to shining metallic green or blue, but usually with long hairs on the thorax that may be white or black. Appearance is generally of rounded body parts. Many are generalists, but also include specialists with hosts in a diverse array of plant families. Because they fly early, many generalist species are managed as pollinators of fruit trees, including apples, cherries, and almonds. They have also been used in pollinating blueberries. As a result of their effectiveness as commercial pollinators, there are several nonnative species in the U.S., imported from Asia. Nesting biology is not known for all species, but it is known that some species nest in the ground, while others nest in plant stems, or holes in wood. Nests are often sealed with a pat of mud or masticated leaf material. All species are solitary, but they may nest gregariously. IN THE WORLD: More than 350 species can be found worldwide; around 145 species occur in North America, with more than 125 species occurring in the West. CLEPTOPARASITES: Stelis. IDENTIFYING FEATURES: Medium-sized, often metallic bees, with rounded thorax and rounded abdomen. May be black or metallic green or blue but are never red or yellow. Females are slightly bigger than males, and males have long, skinny antennae. HEAD: Mandibles are usually robust, especially in females, and may have extra protrusions or modified structures presumed to be used in nest construction. The face may also have small “horns” or other projections; note there are other bee genera that may have facial modifications as well. THORAX: In the place of parapsidal lines seen in most bees, and certainly North American Osmiini, are small indentations; there is no long groove. WINGS: Two submarginal cells. ABDOMEN: No pygidial plate. Scopal hairs are on the underside of the abdomen in females. In males, the apical margin of T6 is usually smooth, with no teeth, notches, or lobes. SIMILAR GENERA: Hoplitis are the most similar-looking bees to Osmia in North America, and several subgenera have been moved between the two genera over the last 100 years. In general, Osmia have shorter bodies. The parapsidal line on the thorax is long and linear in Hoplitis, while short, almost dotlike in Osmia. Hoplitis

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males tend to have more interesting tips on their antennae: clubs, points, hooks, etc. And S6 in Hoplitis has basal, hairless flaps that are not seen in Osmia. Identifying male Osmia to species is very difficult, relying on subjective characters that are best assessed when looking at multiple specimens at once, for comparison. Many of the characters are associated with the size, density, and general character of the punctation, while others are associated with the shape of the propodeal pit (between the abdomen and thorax). Females are a little easier, but many characters are nuanced. The shape and presence of ridges on the underside of the head are diagnostic, as are the particular characteristics of the mandible and its teeth, including the shape of each tooth, their angles, and the distance between them. We include nine relatively common and distinctive Osmia species here, but there are more than 100 western species; in many cases, keys will be needed so that all potential candidates can be considered when a positive identification is required.

— Osmia bucephala Medium to large; 13–16 mm. April through May. FLORAL HOSTS: Visits numerous flowering plants but may have a preference for Asteraceae. RANGE: Widespread throughout North America, occurring as far north as the Northwest Territories and Alaska. Not found in Florida or Gulf states. NESTING: Nests in cavities in wood. Caps nest with a conglomerate of “sawdust” and leaf material. IDENTIFICATION: Larger species, with very light metallic blue shine to a dark body and a large, thick head. HEAD: The clypeus bulges out along its apex, appearing swollen. The head is twice as thick as the width of the SIZE:

PHENOLOGY: Early

Notice how thick the gena is, thicker than the width of the compound eye. The light blue highlights are evident on the face here.

Osmia bucephala (female)

There is a deep groove on the mandible just before it meets the malar space.

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Fine, dense punctation

O. bucephala is very lightly metallic blue.

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eyes. On the mandible, just before it meets the malar space, there is a deep groove. THORAX: Punctation is fine and dense. Females have straw-colored hair covering thorax, while males have white to strawcolored hair. LEGS: In males, the midtarsal segments are flattened and greatly expanded, and the inner hind tibial spurs are much enlarged. ABDOMEN: In females, T1 and the Hair on the male is white, while on the base of T2 have straw-colored female it is yellower. hair, while the apex of T2 through T6 have stout dark hairs. In males, the sides of the apex of T5 and T6 flare out. In females, scopal hairs are black.

Osmia bucephala (female)

Inner hind tibial spur is very large.

SIMILAR SPECIES:

Similar in color and Osmia bucephala general vestiture to (male) Osmia nigriventris, which There is a thin margin that is less common, but overlaps The tarsal segments on the male is impunctate at the apex the range of O. bucephala. are flattened and very wide. of each tergal segment. Osmia nigriventris is completely black, without the slight metallic sheen seen in O. bucephala. While both species have thick heads, O. bucephala is slightly thicker. Osmia bucephala also has more malar space between the bottom of the eye and the beginning of the mandible than does O. nigriventris.

— Osmia cornifrons Small to medium; 8–11 mm. through June. FLORAL HOSTS: Generalist, but common on Rosaceae (Malus, Prunus, and Rubus), and also seen on Ericaceae. RANGE: Native to Asia. Introduced to North America in order to pollinate early blooming fruit trees. Now occurs from Maine south to Georgia and has headed west in recent years, with isolated populations in Colorado, Utah, and, most abundantly, the Northwest. NESTING: Nests in open cavities, including dead wood and reeds; common in bee hotels. SIZE:

PHENOLOGY: March

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Males have light straw-colored to white hair.

Osmia cornifrons (male)

The puncture marks extend across the entire length of each tergal segment — there is no polished rim. This is especially evident on T2.

Even from above, the “horns” on the face are visible.

Osmia cornifrons (female)

The four teeth are visible here; note that none of them sticks out very far. The fourth one curves in and is harder to see.

Light straw-colored hair covers the body of O. cornifrons.

IDENTIFICATION: Smaller Osmia with dark integument and a very slight coppery sheen under thin honey-colored hair on thorax and Osmia cornifrons (male) abdomen. HEAD: In females, two large spinelike projections are obvious, protruding from the sides of the clypeus; between them, on the apical rim of the clypeus is a small pointy projection. Also in females the clypeus is smooth, lacking punctation on its lower half, but densely punctate on the upper half. The face is hairy, with hair descending as far as the tops of the horns. Female mandibles have four teeth, none of which is very pronounced, and the innermost one is curved in, so it is not easily seen. Males have no “horns” on the face. The clypeus has irregular notches in the middle. In males, the first flagellar segment is shorter than the second. THORAX: Punctation is dense and fine. In males, the propodeal pit is shaped like a long rectangle, with

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parallel sides, and some width (not a narrow line). ABDOMEN: In females, the scopae are light yellow or orange to tan (not white or off-white). Each tergal segment is covered in long hairs in females, light yellow on T1–T3, dark brown on T4–T6. In males, the apical margin shows a thin band of white hair, and on T2 pits extend all the way to the apical margin of the segment. SIMILAR SPECIES: The large projections extruding from the face of Osmia cornifrons and O. taurus are unique, separating these two from most other Osmia in the U.S. The two can be difficult to tell apart (so much so that it led to the accidental introduction of O. taurus to the U.S.). Females of O. taurus do not have dense punctations on the upper (basal) half of the clypeus. Females of O. taurus lack the thick hair running across each tergal segment. There may be a small amount of hair; it does not obscure the body below. In males, O. taurus is redder on the abdomen than O. cornifrons. In dead, older specimens, this character fades.

— Osmia lignaria Small to medium; 9–11 mm. through June. FLORAL HOSTS: Generalist, visiting a wide array of plants for pollen. RANGE: Widespread across North America. NESTING: Nests in preexisting cavities in wood or pithy plant stems; has also been seen nesting in old Xylocopa nests, narrow crevices, and abandoned nests of mud or paper wasps. Individual nest cells are partitioned using mud dividers, and completed nests are capped with mud. In many areas, these are common inhabitants of bee hotels. IDENTIFICATION: Deep metallic blue-green species, with mostly light-colored hair on thorax and first one or two segments of the abdomen. HEAD: Pale blue face, covered with white and black hair, with more dark hair at the vertex. The head is slightly thickened, with the width of the gena almost twice as wide as the eye. In females, the clypeus has a deep and wide notch right in the middle, and the malar space is swollen into a projection. The clypeus has some punctation, wide pits that do not touch each other. THORAX: Dark metallic blue, some mixed pale and dark hair on the scutum, but mostly dark hair on the sides of the thorax. Deep, wide pits occur. LEGS: In males, on the midlegs, there is a triangular projection on the femur. Also in males, the hind basitarsus has a tooth. ABDOMEN: Dark, with no apical hair bands. On the first and second tergal segments there are copious white hairs, but the rest of the tergal segments have erect black hairs. In females, scopal hairs are black. SIMILAR SPECIES: The blue-green color and the malar space projections are unique to O. lignaria and make females easy to identify. In males the unique triangular projection on the midfemur is also helpful. There are two subspecies of O. lignaria. Osmia lignaria lignaria has tridentate mandibles, and short horns to either side of the SIZE:

PHENOLOGY: March

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clypeus (in addition to the projections on the malar space). Osmia lignaria propinqua has four teeth, though these are difficult to see, and only small nubs, or no projections, beside the clypeus. Males are difficult to distinguish. Hairs on head are a mix of white and some black. Hair on the thorax and abdomen is mostly white, with some black interspersed. Deep blue-green color

Scopal hairs are black.

Osmia lignaria (female)

Hairs on T1 and T2 are bright white. On T1 through T4, punctation extends evenly across the entire segment.

Osmia lignaria (male)

The clypeus has a deep and wide notch right in the middle.

The malar space is swollen into a projection.

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In males, on the midlegs, there is a triangular projection on the femur.

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— Osmia ribifloris SIZE: Small

to medium; 9–12 mm. spring through August. FLORAL HOSTS: Frequently seen on Mahonia and Berberis (Oregon grape). Also frequent on Ericaceae (Heath family), including Arctostaphylos (manzanita). Used to pollinate blueberries commercially. RANGE: Southern California north to southern Oregon. East to Colorado, Oklahoma, and Texas. NESTING: Nests in preexisting cavities, including old wasp or beetle nests, and bee hotels. Cell plugs are masticated plant materials. IDENTIFICATION: Metallic blue-green bee with black hair. HEAD: Blue-green head, with lots of black erect hair. In females, there are no horns or other protrusions on the face, including the malar space. The mandibles are wide, with several medial teeth, and a cutting edge that is longer than it is wide. The clypeus is flat in profile, and very slightly convex across the lower margin. Males are a slightly lighter shade of blue green, with more white hair intermixed; this is especially evident on the clypeus, and the underside of the head. THORAX: Blue green, with erect black hairs. In males, there are some white hairs PHENOLOGY: Early

Osmia ribifloris (female) Osmia ribifloris (female)

Hind basitarsus about four times as long as it is wide

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intermixed on the scutum. White hair intermixed The sides of the thorax in with a few black hairs on head and thorax males have long white hairs. LEGS: In females, the hind basitarsus is about four times as long as it is wide. In males, the hind basitarsus lacks a tooth. ABDOMEN: Blue green, with no hair bands. In females, Males are a lighter each tergal segment is shade of green blue than females. pitted to the apex of the rim, with Osmia ribifloris (male) polished impunctate bands. Also in females, scopal hairs are black. In males, T1 through T3 have dense white hairs running across the entire segment. Hair becomes darker at the apex of T3 through T6. Also in males, T7 is indented at the center. SIMILAR SPECIES: Females are fairly distinctive, because of the combination of bright blue-green coloration and black hair. There are no projections on the clypeus or malar space. Some similar bees that are relatively common include O. densa, O. laticeps, and O. atrocyanea. Osmia laticeps has a wide band on T2 that is polished and lacks pits. This does not occur in O. ribifloris. Osmia atrocyanea and O. densa are both a deeper indigo blue, and both are restricted to Fabaceae, especially Astragalus (milkvetch).

— Osmia montana SIZE: Small

to medium; 9–14 mm. through June. FLORAL HOSTS: Specialist on Asteraceae. RANGE: British Columbia south to Baja. East to Montana, Wyoming, and Colorado. NESTING: Nests in wood in preexisting cavities. IDENTIFICATION: Dark bee with very slight metallic blue tints. HEAD: Big head, with the gena significantly wider than the compound eye. The malar space is short, nearly absent. In females, the mandible has four teeth, and the ventral margin is greatly elongated so that the mandible is much wider at its apex than where it attaches to the face. In females, the clypeus is polished, with few, if any, pits. The lower rim is modified, with two small projections to either side of center. The clypeus bulges out slightly in the center, so that the lower margin appears to reflex into the face. The labrum is twice as long as it is wide. In males, the first flagellomere is short—less than three-fourths the length of the second. THORAX: Dark, with slight metallic tints. Hair on the sides of the thorax is all black. The scutum is heavily pitted, PHENOLOGY: April

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Osmia montana (female)

There is some thought that some bees, like O. montana, may have evolved to specialize on Asteraceae pollen in order to avoid cleptoparasitic bees that could not ingest this pollen.

with pits almost touching, especially near the sides. WINGS: Wings are smoky. ABDOMEN: Dark, with slight deep metallic blue tints. The first tergal segment has erect long white hairs, and some shorter intermixed dark hairs; both colors are thicker toward the Osmia montana (male) sides (in some specimens, hair is entirely black). Pits are deep and distinct, but small, and there is a band with no pits right at the rim of each segment. In females, scopal hairs are all black. SIMILAR SPECIES: The clypeus, and dark overall appearance of this bee are distinct and hard to confuse with other species. However, there are two subspecies, which differ, in females, mostly in details of the clypeus. In Osmia montana montana, the clypeus is formed near its apex into two teeth, separated from each other by a shallow indentation at the center of the clypeal margin. The hair on the dorsal surface of the thorax in this subspecies is a mix of white and black hair. In O. montana quadriceps, there are no teeth, but instead one median protrusion. The hair on the dorsal surface of the thorax in this species is entirely black. Osmia montana montana is found in the intermountain west, while O. m. quadriceps is found in Pacific states: California, Oregon, and Washington.

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— Osmia californica SIZE: Medium; 9–14 mm. PHENOLOGY: May and June. FLORAL HOSTS: Appears to specialize on Asteraceae (the Sunflower family). RANGE: Widespread throughout the West, but absent, or rare, in hot deserts (Chihuahuan, Sonoran; occasionally found in the Mojave Desert). NESTING: Cavity nesting, in preexisting holes in wood. IDENTIFICATION: Dark blue bee with black stout hair. HEAD: Clypeus dark blue, with pits typically deep and widely spaced. Mostly dark hair, with some white Hairs on top of head mostly interspersed black, with a few white hairs intermixed; in males, hair is predominantly white, with black hairs intermixed. In females, mandibles have four stout teeth. Though hard to see, the area under the head next to the groove that holds Osmia californica the mouthparts is raised into (female) a modest carina. THORAX: Dark blue, with coarse punctation. In females, hairs mostly dark, but a few white hairs are intermixed. In males, hair is long and pale white.

Scopal hairs are black.

Osmia californica (male)

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186  Megachilidae ABDOMEN: Dark metallic blue, polished. Hair on tergal segments is black, except on T1, where it is long and white. In females, scopal hairs are black. In males, there is a small dense patch of black hair on S5. SIMILAR SPECIES: Osmia californica looks very similar to Osmia marginipennis. It can be distinguished, in males, by the dense hair patch on S5, which is not present in O. marginipennis. There are other characters on the genitalia that are not mentioned here. In females, the two are nearly indistinguishable, though usually the pits on the clypeus are more widely spaced in O. californica compared with O. marginipennis, while the carina on the underside of the head in O. marginipennis is bigger than in O. californica.

— Osmia nemoris SIZE: Small; 7–10 mm. PHENOLOGY: May through August. FLORAL HOSTS: Appears to be a floral specialist. RANGE: Pacific Coast and southwest Canada where it can be locally abundant; east to South Dakota. Not found in the Great Basin or Sonoran or Chihuahuan deserts. NESTING: Variable nester; has been found in plant stems, and also in old burrows made by Diadasia species in the ground. IDENTIFICATION: Light metallic bee with pale white hair. Males and females look quite different from each other. HEAD: In females, head is blue with short white hair; gena thicker than width of compound eye. Clypeus is covered in deep, distinct pits, nearly touching. In males, the head is a lighter blue green, with thicker, longer white hair. Also in males, antennae are long, extending This abdomen is not back to tegulae. THORAX: Scutum covered as polished as in some with white to off-white hair, longer in other species. males than females, with more hair on sides than on top. Tegulae are dark. LEGS: Dark, not metallic. ABDOMEN: Blue to green, roughened. In females, white

Osmia nemoris (female)

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hairs cover T1, while light bands of short ivory hair run across the apex of each tergal segment. Also in females, scopal hairs are black. SIMILAR SPECIES: Looks similar to Osmia lignaria but with fewer and shorter white hairs on the thorax, and no protrusions on the face.

— Osmia aglaia

Osmia nemoris

(male) 7–10 mm. PHENOLOGY: Late April through July. FLORAL HOSTS: Generalist, seen frequently on Rubus, and on flowers in the Fabaceae, Orobanchaceae, Plantaginaceae, and Boraginaceae. RANGE: Desert Southwest, north through western Oregon and Washington. NESTING: Cavity nesting, including old twigs from raspberry stems. IDENTIFICATION: Stunning blue, green, and purple bee. Small, but hard to miss. HEAD: Clypeus with dense pits, touching across the surface. The apical margin tapers to a thin edge. The preoccipital margin (the back edge of the head) is carinate: a sharp ridge, rather than rounding gently to the posterior surface. THORAX: Scutum deep green with pits extremely close together on a roughened surface. Tegulae are dark green. Sparse light and dark hairs occur occasionally on the surface of the scutum, with more dark hairs near the posterior half of the thorax. WINGS: Slightly darkened. LEGS: Metallic green/blue throughout, including, in Osmia aglaia females, the hind tibia. (female) ABDOMEN: Deep green often fading to metallic blue. No white hair bands, Osmia aglaia was named by one of the few female but the apical margin of each tergal taxonomists of the early 20th century: Grace segment is pitless and polished. In Sandhouse. She named this stunning bee after one of females, T1 is not covered in dense the three Graces of Greek mythology—the one responsible for creating beauty and brilliance. white hairs.

SIZE: Small;

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SIMILAR SPECIES: This bee is often confused with O. laeta, O. indeprensa, and O. bruneri. In O. bruneri, the hind tibia is brown. In O. indeprensa, the apical margin of the clypeus is thick, not tapering to a thin margin as in O. aglaia. And, among the metallic green Osmia, O. aglaia is one of the few with a carinate margin at the back of the head. Osmia aglaia (male)

PROTOSMIA — SUBFAMILY: Megachilinae — TRIBE: Osmiini OVERVIEW: Unique small black bee, not commonly seen, but easy to recognize if it is. IN THE WORLD: Twenty-six species of Protosmia can be found around the world, but

only one subgenus occurs here: Chelostomopsis. There is one species of Protosmia (Chelostomopsis) in the western U.S.; the other three other species in this subgenus are all found around the Mediterranean. CLEPTOPARASITES: Dioxys. IDENTIFYING FEATURES: Small black bee, rather nondescript on a flower, but with distinct features under the microscope. HEAD: In females, the mandible is long and slender, almost parallel-sided, extending under the clypeus from one side almost to the other. THORAX: The scutum is a little wider than it is long (measured between tegulae). Parapsidal lines are linear. Scutum is dark and finely punctured, usually fairly polished. Forward- and side-facing parts of the thorax are not separated by a strong carina; the front face curves gently around to the side under the wing. There is a carina on the pronotal lobe, or several carinae behind the area where the pronotal lobe would be. Propodeum without a narrow line of pits. WINGS: Jugal lobe less than half as long as vannal lobe. Stigma large. LEGS: Arolia absent. On the hind coxae, there is a longitudinal carina. In females, tarsal claws are simple, not notched. ABDOMEN: The anterior surface of T1 is concave but lacks a carina separating the anterior and dorsal faces. Pygidial plate absent. In males, six tergal segments are visible; the sixth one, when viewed from above, has a strongly projecting lobe at the center but lacks a carina in the area just before the apex. SIMILAR GENERA: Can appear similar to Heriades, especially males, because both have the seventh tergal segment hidden by the large T6. In Heriades males, the abdomen tends to curl under. Heriades, females and males, have a row of large pits running across the propodeum at its base, just under a large carina. Protosmia lack this distinct feature.

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— Protosmia rubifloris SIZE: Small; 7.5 mm. PHENOLOGY: March through early July. FLORAL HOSTS: Generalist, but might have some preference for Salvia (Lamiaceae). RANGE: Washington and California east to Colorado, south to New Mexico. Absent from California deserts. NESTING: Nests in preexisting cavities, including hollows in pine cones. IDENTIFICATION: There is only one species of Protosmia in North America; see the genus description for most characters. HEAD: In females, there is a distinct spoon-shaped projection at the bottom of the clypeus. ABDOMEN: Bright white bands of hair run across tergal Protosmia rubifloris segments at apex. In females, (male) scopal hairs are white. SIMILAR SPECIES: This is the only species of Protosmia in the Americas.

Protosmia rubifloris (female)

COELIOXYS — SUBFAMILY: Megachilinae — TRIBE: Megachilini OVERVIEW: Coelioxys are not common but striking when seen, because of their blackand-white markings and distinctive body shape, which features a very pointed abdomen. Coelioxys are cleptoparasites of Megachile and are mostly associated with wood- or twig-nesting species. In most cases, a female visits a nest while the host bee is away. She uses her pointed abdomen to make an incision in the leaf-lining of a completed nest cell, and then inserts an egg through the opening. She leaves before the host bee returns to build another nest cell, unaware that her finished cells have been usurped. IN THE WORLD: There are 500 species, found on every continent. In the U.S. and Canada there are 46 species, with over 25 occurring in western states. Distinguishing between species of Coelioxys is difficult, involving minute characters that grade into each other. We highlight a few common species, but keys are necessary to verify species identity.

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HOSTS: Megachile. IDENTIFYING FEATURES: Stout bees with a thickened exoskeleton and hair only in thick

white patches that stand out starkly on the matte-black thorax and abdomen. HEAD: The compound eyes are covered with minute hairs. THORAX: The lateral plates behind the scutum (axilla) are extended into points that hang out over the scutellum, and perhaps to the propodeum. WINGS: Often a dusky gray. Two submarginal cells. ABDOMEN: Extremely pointed abdomen, in which the sixth sternal segment is elongated, almost beyond the length of the final visible tergal segments; in males, there may also be four to eight teeth or spines. The first tergal segment has a sharp concavity on the side that faces the thorax, delineated by a sharp ridge. A few species show red coloring on the first few segments of the abdomen, and some have red legs. SIMILAR GENERA: Few genera resemble Coelioxys; the pointed abdomen is very distinct, as are the acute axilla. Dioxys may appear somewhat similar in the matted hair and red legs. The abdomen on Dioxys does not taper as notably, and the axillae are not pointed.

— Coelioxys edita SIZE: Small

to medium; 9–14 mm. through September. FLORAL HOSTS: This bee is a cleptoparasite of Megachile and has no pollen preferences. It can be seen on any summerflowering plants. RANGE: Widespread throughout the West and into southern Canada. Seldom seen in the Great Basin. NESTING: Usurps the nests of female Megachile, many of which are in preexisting cavities in wood. IDENTIFICATION: Medium-sized black and white bee, striking for the elongated The axilla has and pointed abdomen. HEAD: Black, with a small carina on the upper surface. appressed white hairs on clypeus, frons, and some on the gena. Head is coarsely pitted, with pits very close together. The gena is narrower than the eye. In females, on the clypeus, there are two teeth on the margin that can be seen with a microscope through the appressed Coelioxys edita hairs. THORAX: The sides of (female) the thorax are covered in PHENOLOGY: Mid-April

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T2 and T3 have an indented groove running across the center of the segment.

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Coelioxys  191

very dense deep pits, with T6 has all spines some scattered scalelike about the same hairs over the top. The length, short and stout. posterior margin of the scutellum is slightly indented (in most specimens). The axillae have a small carina on their upper surface. LEGS: Hair on the legs is all white, but golden on the Coelioxys edita tarsi. The forecoxa has a (male) conspicuous spine, rounded at its tip. In males it is covered with appressed white hairs. ABDOMEN: The second and third tergal segments have conspicuous grooves running from side to side. The first through fifth tergal segments have very strong apical hair bands made of appressed hairs. On T1 there is no hair on the basal surface, though appressed hair creates patterns across the rest of the surface. In males, T6 has all spines about the same length, short and stout for both the dorsal and ventral spines. SIMILAR SPECIES: Most similar to C. bisoncornuus; that species does not have carinae on the axillae and the scutellum bulges out, rather than being slightly indented, as in C. edita.

— Coelioxys octodentatus SIZE: Small

to medium; 7–12 mm. through September. FLORAL HOSTS: This bee is a cleptoparasite of Megachile and has no pollen preferences. It can be seen on any summer-flowering plants. RANGE: Widespread; from coast to coast, and Canada south to Mexico. NESTING: Has been found in nests of Megachile brevis and M. mendica, both of which nest in a variety of preexisting cavities, including soil, stems, and wood. IDENTIFICATION: Slightly larger Coelioxys seen throughout the U.S. and Canada during the summer. HEAD: Black integument, occasionally with some dark red on the scape and pedicel. In males, relatively long white hair covers the face. Lower margin of clypeus is straight, indenting only slightly; in profile the clypeus sticks out from the head slightly (though in males, clypeal characters are hard to see through the hair). Gena slightly narrower than width of compound eye. Pits are deep and variably scattered, mostly visible on the vertex. Hairs on the compound eyes are short. THORAX: Scutum covered with deep, wide pits, seen PHENOLOGY: May

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Coelioxys octodentatus (female) White apical hair bands run across T1–T5; more conspicuous on T2–T5 than on T1.

through the thin and sparse hair. The posterior surface of the scutellum is bare of hair. Tegulae are black most of the time; occasionally red. Axillae are produced, but small, not drawn into long points. LEGS: In Coelioxys octodentatus (male) males, the front coxa has a long broad spine. Tibia, tarsi, femur dark red to dark brown; not black. ABDOMEN: Each tergal segment is dark. White apical hair bands run across T1–T5, more conspicuous on T2–T5 than on T1. On T2–T3 there are grooves running the width of the segment. In females, T6 is broadly rounded at its apex. Also in females, S1–S5 are usually red at their apices (some individuals are black). In males, the dorsal spines on T6 are long and slender, longer than ventral spines. SIMILAR SPECIES: In the West, males of this species are indistinguishable from C. novomexicanus. And males of both species appear similar to C. pratti, but that species has long hairs on the compound eyes. Coelioxys rufitarsis and C. novomexicanus females also appear similar to C. octodentatus. Coelioxys rufitarsis has longer hairs on the compound eyes than does C. octodentatus, and has velvety patches on T6, which are not seen on C. octodentatus. Typically, females of C. novomexicanus have a deep indentation on the clypeus, and the apical margin has a dense fringe of yellow appressed hairs; this is lacking in C. octodentatus.

— Coelioxys rufitarsis SIZE: Medium to large; 12–18 mm. PHENOLOGY: June through September. FLORAL HOSTS: This bee is a cleptoparasite of Megachile and has no pollen preferences. It can be seen on any summer-flowering plants. RANGE: Widespread throughout the U.S., reaching far north into Canada, including the Northwest Territories, Manitoba, and Quebec. Largely absent from the lower Mississippi Basin, and the Sonoran and Mojave deserts. NESTING: Usurps the nests of female Megachile, including M. latimanus, M. texana, M. montivaga, and M. melanophaea, all of which nest in the soil.

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IDENTIFICATION: Striking black-and-white bee with pointy abdomen, most likely seen on flowers in summer months. HEAD: Black, with appressed white hairs over a coarsely pitted face. Hair is especially thick around antennal sockets and behind the front ocellus. Gena is thinner than the width of the compound eye. Clypeus is flat, the lower margin bumpy, but without any produced teeth. THORAX: Scutum has thin, erect hair at its center. Scutellum gently rounded at its posterior margin, with no indentations. Axillae thin, pointing out from scutellum at a slight angle. LEGS: Tarsal segments are bright red, and sometimes the tibiae and femora are as well. Spines on forecoxae reduced to short little protrusions. ABDOMEN: The second and third tergal segments have conspicuous grooves running from side to side. The first through fifth tergal segments have very strong apical hair bands made of appressed hairs. On T1 there is no hair on the basal surface. In females, T6 is angled with very small hairs on the sides that look like white velvet when viewed from above. In males, T6 has a deep median indentation, the teeth to either side are short and Tarsal segments angle away from each other slightly. are bright red. The teeth underneath (ventrally) are longer, parallel, and pointier. SIMILAR SPECIES:

May appear similar to C. alternatus, which also has red tarsi. Coelioxys alternatus has less erect hair on the scutum, and thinner hair bands running across each tergal segment.

Coelioxys rufitarsis (female)

Coelioxys rufitarsis (male)

Tarsal segments are bright red.

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194  Megachilidae

MEGACHILE — SUBFAMILY: Megachilinae — TRIBE: Megachilini OVERVIEW: Gray to matte-black bees, small to medium-sized, often with a fuzzy thorax and stripes across the abdomen. Incredible diversity in form and body shape. Usually seen in the summer. Include specialists and generalists. Most nest aboveground, including in preexisting cavities, pithy stems, and decomposing wood; they are frequent occupants of man-made bee nests. Some species nest in the ground. Most species use pieces of leaf to line nest cells, protecting eggs and pollen provisions. A few use resin. Some species are used commercially for the pollination of crops, including alfalfa. Though nesting is solitary, nesting aggregations are not uncommon, with many females nesting near each other (especially in bee hotels). IN THE WORLD: More than 1,520 species can be found around the world. They occur on every continent as well as most islands. In North America there are more than 140 species, most occurring in the western U.S. More than 100 species occur in the West. CLEPTOPARASITES: Coelioxys. IDENTIFYING FEATURES: Chunky dark bees, never metallic, with white hair bands across the abdomen. HEAD: The mandibles have three to five teeth. THORAX: Generally wide, and the transition from the dorsal face of the propodeum to the anterior face is abrupt. WINGS: Two submarginal cells. LEGS: No arolium between the tarsal claws. In males, the front coxae usually have small spines, and the front tarsal segments are often modified. ABDOMEN: The first tergal segment is gently concave, but there is no ridge around it, with the transition to the dorsal face being smooth. Females have copious scopae on the underside of their abdomens. In males, the sixth tergal segment turns down abruptly, forming a noticeable rim. SIMILAR GENERA: Lithurgopsis, which is slightly longer, has arolia, and also large projections (almost like horns) on the front of face. No Megachile fit this combination of characters. Ashmeadiella, Heriades, Chelostoma, and other small dark Osmiini may appear similar to small Megachile. Osmiini have an arolium between the front claws. Megachile do not. Finally, larger darker Megachile may appear similar to Xylocopa. Xylocopa have three submarginal cells, while Megachile have two. Distinguishing between species of Megachile can be difficult. In males, characters are often on the sternal segments and can be difficult to see in photos or on less-than pristine specimens, and in females, characters are on the mandibles, which may be worn and difficult to see. There are a few species that stand out. We highlight some of the more easily discernible members of the genus, as well as several of the most commonly seen, but for most accurate identifications, it is best to use a key that includes all species.

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— Megachile brevis SIZE: Small to medium; 7–12 mm (males are much smaller than females). PHENOLOGY: July through mid-October. FLORAL HOSTS: Polylectic, but with preference for Asteraceae. RANGE: Widespread throughout North America. NESTING: Any hollow tunnel, including grass stems, cornstalks, Helianthus, Erigeron, Vernonia, Cirsium, Ambrosia stems, termite holes in wood, in mats of grass, under dry cow patties, or in holes in the ground. Nests are lined with leaf material, especially from Rosa, or petal pieces. IDENTIFICATION: Medium-sized black bee, with some rust-colored and some yellow hair on the head and thorax, and strong white bands of hair on the abdomen. HEAD: In females, there are four teeth on the mandible, with the third one reduced to a very small point. In males, the mandible has three teeth and the face has thick white or ivory-colored hair. THORAX: There is white hair near the posterior end, though the scutum has black hairs. LEGS: In males, the legs are slender, simple, and mostly black. On the forecoxae there are small spines. The tarsi are dark brown to black. ABDOMEN: In females, the abdomen is slightly flattened, wider near T2 and T3 than it is at the base; thin bands of hair run across T3–T6. The second tergal segment is polished near the center, with some pits on the sides. In profile, T6 is very concave, Scopal hairs are white to off-white.

T6 in females is notched, rather than continuously tapering.

Megachile brevis (female)

The hair on T2 is black, before the apical hair band. Some gray/white hair on the thorax and head of M. brevis

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196  Megachilidae The hair on males is slightly tanner than on the females of the same species. T6 of male M. brevis has a patch of thick white hair, and a notch in the center.

and has white appressed hairs on its apex. Also in females, the scopal hairs are ivory white, and no other lines of hair occur beneath the scopal hairs, but there are some black hairs on S6. In males, T6 has flattened white woolly hairs near its tip. Tarsal segments Megachile brevis Underneath, S6 has some are brown. (male) black flattened hairs. SIMILAR SPECIES: Megachile brevis looks similar to M. onobrychidis, M. pseudobrevis, and M. coquilletti. Females of M. coquilletti and M. onobrychidis have completely black hair on S6. None of these species has flat thick white hairs on T6 in males. Megachile coquilletti has yellow tarsi, instead of brown or black in males.

— Megachile inermis SIZE: Medium

to large; 11–20 mm. June through

PHENOLOGY: Early

September. FLORAL HOSTS: Generalist. RANGE: Occurs as far north as the Northwest Territories and Alaska. South through New Mexico and east to Maine and Georgia; entirely absent from the southern Great Plains states. NESTING: Preexisting cavities and rotting logs, which females will apparently chew into as they make their nests. IDENTIFICATION: Larger gray Megachile; often found in bee hotels. HEAD: In females there are five teeth, with a poor distinction between the second and third. At the bottom of the clypeus there is a broad protuberance. The gena is wider than the compound eye, making the head appear thick. In males, the mandibles have three teeth; the second one is closer to the first than the third. In both sexes, the vertex is wide. THORAX: Covered in mostly pale hair with some short black hair at the center of the scutum and scutellum. In females, the pits on the scutum are close together and distinct. LEGS: In males, the front tarsi are simple, and dark. There is a spine on the forecoxae, but it is hidden beneath thick hair. ABDOMEN: In females, the abdomen is slightly flattened, wider near

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T6 is not particularly concave.

Scopal hairs pale Megachile inermis (female)

Megachile inermis

T2 and T3 than it is at the (male) base; thin bands of hair run Thin bands of hair across T3–T6. In profile, T6 run across T3–T6. is not particularly concave, and has short brown hairs that lie flat on its surface. The scopal hairs are pale to ivory. In both sexes, T1 is covered in thick off-white hair. SIMILAR SPECIES: Megachile Front tarsi inermis females appear most simple and dark similar to M. centuncularis, M. lapponica, and M. relativa. They can be distinguished by the differences in the vertex on the head. In all three, the lateral ocelli are closer to the top of the head than they are to the compound eyes, because the vertex is less broad. Males are similar to M. montivaga, but that species has three teeth on the mandible that are equally spaced.

— Megachile montivaga SIZE: Small to medium; 9–13 mm. PHENOLOGY: Early June through September. FLORAL HOSTS: Generalist. RANGE: Widespread throughout the U.S. and southern Canada; rarer farther north. Largely absent from the Great Basin. NESTING: Most commonly nests in the soil, but may occasionally nest in “bee hotels.” Consistently uses flower petals instead of leaves in nest construction. IDENTIFICATION: Medium-sized bee, strikingly black compared with many other Megachile. HEAD: In both sexes, the lower margin of

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Megachile montivaga (male)

T6 protrudes at the center.

Front tarsi straight and dark

Megachile montivaga (female)

the clypeus is smooth, without a projection at the center. In females there are five teeth on the mandible, though the second tooth is not well defined, so that it often appears to have four teeth. Under a microscope, the teeth do not appear to be beveled for cutting; this is especially apparent Megachile montivaga between the second and third (female) T6 concave teeth. The gena is narrower than the width of the compound eye. In males, there are three teeth, all equally spaced. THORAX: Hairs on the thorax are almost all light colored, and thick. In females, the pits Scopal hairs on the scutum are close together and light distinct. LEGS: Males have dark, straight front tarsi. The forecoxa has a very pointed tooth. ABDOMEN: In females, the abdomen is slightly flattened, wider near T2 and T3 than it is at the base; thin bands of hair run across T3–T6. Also in females, T6, when viewed in profile, is very concave. The scopal hairs are all light colored. In males, T6 protrudes at the center. SIMILAR SPECIES: Males appear most similar to M. inermis. That species has three teeth as well, but the second and first are closer together than the second and third.

— Megachile rotundata SIZE: Small; 7–9 mm. PHENOLOGY: June through October. FLORAL HOSTS: Polylectic, but widely used in the northeastern U.S. and Canada to pollinate lowbush blueberry (Vaccinium). Excellent pollinator of alfalfa in western states. RANGE: Introduced from Europe in the 1940s; widespread throughout North America. NESTING: Cavity nester, often

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gregariously, takes readily to humanmade holes in wood, or paper straws. IDENTIFICATION: Slightly smaller species than other common Megachile. HEAD: In females, the mandible has four teeth. The clypeus rim is slightly thickened, but straight (not concave at the center). THORAX: Punctation is very dense, and especially coarse in the center.ABDOMEN: Thin white hair bands run across each tergal segment. The second tergal segment has thick patches of very short hair covering the surface on either side of center (often most visible when viewed at a slight angle). In females, the scopa is white to golden orange; underneath the scopal hairs there are white hair bands. The third and fourth tergal segments have thick black hairs laterally. The sixth tergal segment is flat, or slightly concave, but not notched; there are short black bristles on this segment. In males, T6 is jagged to round, but not deeply notched. SIMILAR SPECIES:

Megachile apicalis shares many similar features, but it is slightly larger. In females, the clypeus is concave in the middle. In both males and females, T2 and T3 have oblong patches of thick white hair laterally. In M. rotundata, the white hair patches are only on T2. Megachile mendica also looks

Megachile rotundata (female)

Megachile rotundata (female)

White hair bands run across each tergal segment.

The sixth tergal segment is slightly concave.

The sixth sternal segment is all black hairs. Underneath the scopal hairs there are thin white hairs.

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Megachile rotundata (male)

The sixth tergal segment ends in a jagged line without a deep notch in it.

similar; in males T6 has a deep notch in the center, unlike M. rotundata. Megachile texana may also look similar, but the scopal hairs are bright white and puff out to either side in this species.

— Megachile relativa SIZE: Small

to medium; 9–12 mm. through early fall. FLORAL HOSTS: Generalist. RANGE: Ranges from northern Canada and Alaska south to Mexico. Largely absent from the eastern half of the Great Plains, and from the Sonoran and Mojave deserts. NESTING: Nests in preexisting cavities, including bee hotels. IDENTIFICATION: Dark bee of medium to small size. One of the more common western species. HEAD: In females, the mandibles have five teeth. The gena is slightly thicker than the width of the compound eye. The lower margin of the clypeus is entirely straight. In males, the mandible has three teeth. On the straight margin of the clypeus in males, there is a small Megachile relativa (female) central protrusion. THORAX: Covered in light Hairs on T6 an orangish red hairs, with a few black intermixed on the scutellum. LEGS: In males, the forelegs are not inflated. The inner and outer tarsal claws are about the same sharpness. The midtibial spur is short, but clearly visible. ABDOMEN: In females, the PHENOLOGY: May

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apex of each tergal segment is lined with short white hairs, slightly thinner in the middle than on the sides. The sixth tergal segment has thick, erect reddish hairs. Scopal hairs are light yellow, and sparse, pale Megachile relativa yellow on S6. Overall, the (male) abdomen does not appear parallel-sided. SIMILAR SPECIES: Megachile relativa females appear most similar to M. centuncularis and M. lapponica females. With M. centuncularis, the hairs on T6 are black, and not Forelegs not red gold. With M. lapponica, inflated the scopal hairs on S6 are black. Males of M. relativa can appear similar to males of M. inermis, M. centuncularis, and M. lapponica. With M. inermis, the three teeth are not evenly spaced, as they are in M. relativa; the middle tooth is closer to the first tooth than the last. The central protrusion on the clypeus of M. relativa males is missing in M. centuncularis. Also, the inner tarsal claw is more pointed than the rounded outer one. M. lapponica and M. relativa males are so similar that they can be distinguished only through characters on the genitalia.

— Megachile policaris SIZE: Medium; 12–15 mm. PHENOLOGY: Late March through August. FLORAL HOSTS: Generalist, often found on Asteraceae and Fabaceae. RANGE: Southern U.S., from California to Florida. North as far as Illinois and Utah. NESTING: Nests in preexisting cavities, including fence posts, and other manmade wood structures. Nests sometimes consist of brood-chambers, with multiple larvae feeding on one large pollen mass, instead of individually partitioned nest cells. IDENTIFICATION: Larger dark leaf-cutter bee. HEAD: In females, lower margin of clypeus with small protrusions to each side of center. Hair on the clypeus of females is entirely pale. The mandible has four teeth. In males, the mandible has three teeth. THORAX: In females, hair on anterior half of thorax is light, fading to a tawnier color toward the scutellum. In males, hair is light throughout. LEGS: In males, front legs are yellow. The third segment of the fore basitarsus is produced into a long plate that overlaps the other segments. Midlegs are rust red. Hind legs are black. ABDOMEN: In females, abdomen with parallel sides, with T2 as wide as T4. Thick pale hair covers T2–T4.

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Megachile policaris (male) Front legs yellow

Fore basitarsus is produced into a long plate. Abdomen with parallel sides, with T2 as wide as T4

That of T5–T6 is darker, and more erect. In females, scopal hairs yellow, with those on S6 black. Megachile policaris SIMILAR SPECIES: Appears (female) most similar to M. fidelis. Females of M. fidelis have conspicuous flattened protuberances on either side of the clypeus that should distinguish that species. In males, the white hair on T5 and the brush of dark hairs on the fore basitarsus are distinctive.

— Megachile pugnata SIZE:

Medium to large; 12–18 mm. Early June through October, depending on latitude. FLORAL HOSTS: Specializes on sunflowers (Helianthus sp.). RANGE: Throughout North America, ranging from subarctic Canada south to New Mexico, southern California, and Georgia. NESTING: Pre-excavated holes, including man-made nests and bee hotels. IDENTIFICATION: Conspicuous black-and-white bee with giant mandibles. HEAD: In females, the clypeus is short and thickened, so that it looks almost shelflike on the face. The mandibles are exceedingly long, with five teeth, though the fourth is quite small and hard to see. On the gena, there is a tooth on the lower margin. In males, the mandible has three teeth. THORAX: Scutum is covered in short dark hairs, outlined with lighter hairs, especially anteriorly. LEGS: In males, the front tarsus is bright yellow. The basitarsus PHENOLOGY:

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Bright stripes run across the apex of each tergal segment.

Short clypeus Very long mandibles Megachile pugnata (female)

is dramatically expanded and carved out, fringed with long ivory/blonde hairs. Also in males, the midtibial spur is clearly evident. Megachile pugnata (male) ABDOMEN: In females, bright white stripes run across the apex of each tergal segment. Scopal hairs are light blonde. In males, white stripes extend across the apex of each tergal segment too, being quite dense along the margin of T4 and T5. Away from the edge, T3–T5 have stiff, erect black hairs near the center. Basitarsus is dramatically expanded and carved out, fringed with SIMILAR SPECIES: Few female Megachile resemble long ivory/blonde hairs. M. pugnata, with her large mandibles, toothed gena, and shortened clypeus. With males, M. mellitarsis can appear similar. Megachile mellitarsis lacks a band of white hairs on T5, which appears on males of M. pugnata. Megachile pugnata also appears similar to M. fidelis. Megachile fidelis has dark thick hairs on the fore basitarsi, which are lacking in M. pugnata males.

— Megachile frigida SIZE: Medium; 11–15 mm. PHENOLOGY: June through early September. FLORAL HOSTS: Generalist. RANGE: Widespread throughout the U.S. and into northern Canada and subarctic Alaska. Extends south through New Mexico, and into Florida, but largely absent from western half of eastern deciduous forests. NESTING: Appears to prefer decaying wood; also found in bee hotels.

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IDENTIFICATION: Common midsized Megachile; females are typical, but males have pale, flattened front legs that are distinctive. HEAD: In females, the mandible has four teeth. The top tooth is flattened, and indistinct; almost square-shaped. THORAX: The thorax is outlined by tawny to pale hair. Though hard to see, in males, on the side of the body below the wings, there is a light-colored carina that outlines a concavity. LEGS: In females, the midtibia has orange hair, similar in color to that on the scopa. In males, the front femur is flattened, and hollowed out. It is ivory to yellow in color with two longitudinal stripes of brown on the front side, and a fringe of yellow hair on the back side. ABDOMEN: Thin short bands of hair line the apex of T1–T4, and T1 and T2 are also covered in pale erect hairs that cover the surface almost entirely. In females, scopal hairs are Megachile frigida deep yellow, except (female) on S6, where there are also dark hairs. In males, T6 has an indentation at the center, is broad, and has no teeth to either side. SIMILAR SPECIES:

Several bee species in the subgenus Xanthosarus have males with front tibiae modified as in this bee. None have the brown markings on the front femur like this species. For females, the shape of the mandible is distinctive.

Midtibia has orange hair, similar to that on the scopa.

Front tarsi flattened and light

Light-colored front femur is flattened and hollowed out.

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Megachile frigida (male)

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— Megachile perihirta SIZE: Medium;

12–15 mm. June through early September. FLORAL HOSTS: Generalist, but common on Asteraceae and Fabaceae. RANGE: Nebraska south through Texas, west to California and north through southern British Columbia and Alberta. NESTING: Nests in the ground. IDENTIFICATION: Midsized leafcutter bee; males have large brushy hairs on forelegs. HEAD: In females, there Megachile perihirta are five teeth on the (female) mandibles. The fourth tooth is parallel-sided. In males, the head is covered in thick, long, light-colored hair. THORAX: In females, on the thorax, and especially the scutellum, the hair is black, though the sides of the thorax are rimmed in pale hairs. In males, the hair on the thorax is all pale. LEGS: In males, the front tarsus is yellow, and the basitarsus is broad, and inflated at its base. There is a fringe of pale yellow, long, thick Yellow front tarsus hair on the front tarsus. The with broad basitarsus foretibia is rust red. There is no midtibial spur, but the mid basitarsus is strongly angled, but not toothed. ABDOMEN: In females, T2 and T3 are wider than T4 and T5, giving a tear-drop appearance. Also in females, scopal hairs are long, visible from above as they stick Megachile perihirta out on the sides, and orange, (male) becoming a lighter yellow on S6. In both sexes, T1 through PHENOLOGY: Late

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T1–T3 covered in long pale hairs

Scopal hairs long and orange

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T3 are covered in pale longer hairs. In females, thin hair bands occur on T3–T4, but they are interrupted at the center. SIMILAR SPECIES: Most similar to Megachile dentitarsus and M. latimanus. Megachile dentitarsus has small sharp spines on the underside of the thorax, and the mid basitarsus has a large protuberance, square in shape. Megachile latimanus is also very similar. It is more common in eastern states, though there is considerable overlap in their ranges. Females of the two are nearly indistinguishable; in males, M. latimanus has a large protuberance on the mid basitarsus that differs from the keel-shaped protrusion in M. perihirta.

DIOXYS — SUBFAMILY: Megachilinae — TRIBE: Dioxyini OVERVIEW: Dioxys are small black bees with white stripes on the abdomen. In females, the abdomen tapers slightly. Though rather unobtrusive and seldom seen, they are widespread throughout western North America. They are cleptoparasites of other bees in the family Megachilidae. IN THE WORLD: There are 15 species of Dioxys; 10 occur in northern Africa, southern Europe, and central Asia. Five are found in western states and provinces of North America. HOSTS: Anthidium, Megachile, and Osmia. IDENTIFICATION: Small black bees, sparsely haired, and with thin hair bands on the abdomen. HEAD: The labrum is extremely long. There is a pronounced preoccipital carina. In both males and females, the mandible has two teeth, and is very slender. THORAX: Where the front face of the thorax meets the side face (the mesopleuron), there is a strong carina (the omaulus); in addition, the pronotal lobe is carinate. On the thorax especially, hair is long but matted, looking as though the bee hasn’t washed in days. In many species, the tegulae are red. On the metanotum, there is a spine right at the center; this character is unique among Megachilidae. The axillae are rounded, or only very minimally pointed. WINGS: There are two submarginal cells. LEGS: Red in many species. ABDOMEN: Gently but notably tapers. In females, S6 is broad and extended, close to the same shape as T6. SIMILAR GENERA: Dioxys bear a passing resemblance to Coelioxys; both have pointy abdomens, black bodies, with white abdominal stripes, and lack scopal hairs. Coelioxys have abdomens that are more angular than Dioxys, they lack the central spine on the metanotum (but the axillae are extended as two points), and their compound eyes have minute hairs.

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— Dioxys pomonae SIZE: Small; 5–10 mm. PHENOLOGY: March through June. FLORAL HOSTS: Does not collect pollen for offspring; generalist. RANGE: Most common in California, north through Oregon, Washington, southern British Columbia, east to Texas, and North Dakota. NESTING: Lays eggs in the nests of Megachilidae; likely Osmia. IDENTIFICATION: Small dark bee, seldom seen. HEAD: Black. The eyes converge slightly toward the bottom. THORAX: Covered in sparse, short Dioxys pomonae (female) white hairs. Tegulae may be dark red or black. Pronotal lobe moderately carinate anteriorly, but not so strong that it appears to separate the two faces of the pronotum. WINGS: Slightly smoky. LEGS: Usually black, but may be red. ABDOMEN: In females, T1 has an apical hair band made of short white hairs. Also in females, T6 is Dioxys pomonae (male) triangular and not elongated, with just the tip drawn to a small triangular point, matched ventrally by the shape of S6. In males, the apical hair bands on the tergal segments are very narrow. Also in males, T6 is short and wide, with the apical margin very weakly bilobed. SIMILAR SPECIES: Dioxys pacificus may appear somewhat similar, but the unique shape of T6 in females should distinguish; it is much shorter and more angled in D. pomonae females, while it is more elongate and rounded in D. pacificus. There are two subspecies of D. pomonae: Dioxys pomonae pomonae has black legs, and T2 is black. It is the more widespread of the subspecies. Dioxys p. timberlakei is found in the Mojave Desert and has red legs and red on T2.

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— Dioxys productus SIZE: Small

to medium; 6–11 mm. through May at lower latitudes; May through July farther north. FLORAL HOSTS: Does not collect pollen for offspring; generalist. RANGE: Widespread in the Southwest and north to Idaho and Montana along the Rocky Mountains. Absent from the Pacific Northwest and does not extend to Canada. NESTING: Lays eggs in the nests of Megachilidae; likely Osmia. IDENTIFICATION: Small dark bee, seldom seen, but with unique hair patterns. HEAD: Black. Eyes converging toward the bottom. THORAX: Pronotal lobe very carinate on the anterior margin, so that it appears completely separated from the rest of the pronotum. WINGS: Tinted brown. LEGS: Black, or red in some individuals. ABDOMEN: Black in most individuals, though in some there is extensive red. In females, T1 has an apical hair band of white, rather long hairs, especially toward the center. Also in females, S6 and T6 are about the same length and size; elongated, with parallel sides, and the apex is rounded gently, like a half-moon. SIMILAR SPECIES: Dioxys productus females are unique because of the carina on the Long straight hairs pronotal lobe; this is not found in other on the apex of T1 species. Males of Dioxys species can be difficult to tell apart unless the genitalia are visible. There are three subspecies of D. productus. Females are distinguishable, but PHENOLOGY: March

Dioxys producta (female)

Dioxys producta (female)

Dioxys producta (male)

S6 and T7 are about the same length and size.

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Legs may be black or red.

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males can be difficult to tell apart. Dioxys productus productus females have almost entirely black abdomens and are found in the Great Basin. Females of D. p. cismontanicus have a red abdomen, and the apical hairs at the center of T1 are short (this subspecies is found in mountains of California and northern Baja California). Females of D. p. subruber also have a red abdomen, but the apical hairs at the center of T1 are very long (this subspecies is found in the deserts of the Southwest).

ANTHIDIELLUM — SUBFAMILY: Megachilinae — TRIBE: Anthidiini OVERVIEW: Anthidiellum are tiny but robust black-and-yellow or red bees, known for hovering conspicuously near plants before landing. They are abundant in the summer but are generalists and will visit many different kinds of flowering plants. Nests are external structures attached to rocks, branches, or leaves. Nest is made of resinous material and is shiny, fairly smooth, and not always large, containing only one or two cells. Males are hard to miss, as they establish territories and patrol constantly, flying in a straight line for several meters and then hovering in place for a period, before flying in another direction to a new spot to hover. If an insect or other “intruder” is spotted, males will bowl into them. Patrolling is broken up by periods of time resting within his territory or taking nectar from flowers. IN THE WORLD: Around 70 species can be found around the world, ranging from northern Mongolia and Finland to South Africa and Australia. Five species occur in the Americas, with four of them in western North America. CLEPTOPARASITES: Stelis. IDENTIFYING FEATURES: Small robust Anthidiellum species have a shelf at bees with notable yellow-and-black the back of their head; sometimes it is thick, but in other species it is paper thin. stripes. In flight, Anthidiellum appear smaller and more compact than other In Anthidiellum the scutellum is also elongated, extending over the propodeum insects as they tuck their appendages and hiding the end of the thorax and in very tightly. HEAD: Has a shelflike the beginning of the abdomen. ridge behind the ocelli, hanging out so far as to almost cover the beginning of the thorax in some species. The subantennal suture is unique among Anthidiini in being strongly outwardly curved. In females, the mandible has four teeth, and males have three. THORAX: Scutellum is swollen, extending out over the propodeum.

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210  Megachilidae WINGS: Long, extending past the end of the body. LEGS: Arolia between front tarsal claws. In males, on the hind coxa, there is no spine. ABDOMEN: Scopal hairs on sternal segments. SIMILAR GENERA: Dianthidium are similar in size and coloring, but Anthidiellum lack the pronotal lobe modifications seen in Dianthidium. In addition, the hind coxa in males on Dianthidium has a notable spur, which isn’t present in Anthidiellum. Anthidium, though similar in coloration, are generally larger, have more teeth in their mandibles (five or more), and lack an arolium. Paranthidium has a rounded preoccipital ridge, and it is not shelflike, as in Anthidiellum.

— Anthidiellum notatum SIZE: Small; 7–8 mm. PHENOLOGY: April through mid-September. FLORAL HOSTS: Polylectic, visiting a wide variety of plants for pollen and nectar. RANGE: Widespread; New Hampshire to Florida, west to California. NESTING: Cavity-nesting; has been found in beetle burrows in Douglas fir (Pseudotsuga). IDENTIFICATION: Small compact bee with yellow markings on thorax, head, legs, and abdomen. HEAD: In females, the apical margin of the clypeus is relatively flat, not dipping much lower than the level of the compound eyes. Also in

The wings are long, relative to the length of the body.

Covered with dense pits

Anthidiellum notatum (female)

The yellow markings on the face that occur behind the ocelli end about where the head rounds to the sides.

Anthidiellum notatum (male)

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females, the yellow markings on the face that occur behind the ocelli end about where the head rounds to the sides. In both sexes, the area between the ocelli is polished, and swollen, appearing as a modest bump on the top of the head. In males, the clypeus is usually very yellow. THORAX: Scutal punctures are rough throughout. WINGS: Dark, long. LEGS: Almost entirely yellow. ABDOMEN: In males, the pygidial plate is lobed. SIMILAR SPECIES: There are four subspecies of A. notatum found across North America; two are found in the West. Anthidiellum notatum gilense females have a hind tibia that is red/yellow, with no black markings. Anthidiellum notatum robertsoni females have a hind tibia that is yellow, with black markings. Anthidiellum ehrhorni looks similar to A. notatum but is less common and slightly smaller. In A. ehrhorni males, T7 has two lateral lobes and two fingerlike projections at the center. In females, the apex of the clypeus dips low in the center.

ANTHIDIUM — SUBFAMILY: Megachilinae — TRIBE: Anthidiini OVERVIEW: Known as wool carder bees, Anthidium are distinctive, noisy, yellow-andblack bees seen abundantly in summer months. Most are generalists, but a handful of specialists are also known among western species. Western species nest in a wide variety of cavities, including beetle tunnels, yucca stalks, and tree stumps, and also in the ground. All of them use plant hairs (trichomes) that they “shave” from woolly plants to pad nest cells. IN THE WORLD: Anthidium are most abundant in the Northern Hemisphere (Europe, northern Asia, and North America). They can be found in northern African countries, South America, and India, but are absent from Australia, Indonesia, and the tropics of southeastern Asia. More than 160 species occur in the world. There are 92 species in North, Central, and South America, and more than 30 in western states and provinces. Among them are several introduced species. CLEPTOPARASITES: Stelis, Dioxys. IDENTIFYING FEATURES: Yellow-and-black medium-sized bees with pollen-collecting hairs on the underside of the abdomen of females. Body segments are round to cuboid, giving them a robust appearance. HEAD: Mandibles of females have between five and seven small teeth. In both males and females, the subantennal suture is very straight. The back of the head rounds gently, with no strong carinae or ridges. THORAX: Pronotal lobe is rounded, with no paper-thin ridges. Scutellum is not overly inflated or shelflike. WINGS: Two submarginal cells (as in all Megachilidae). LEGS: No arolium between the front claws. ABDOMEN: In males, teeth occur laterally on T5 and T6. SIMILAR GENERA: Anthidiellum may be similar in terms of the yellow-and-black striping. Anthidiellum is generally smaller and has an enlarged scutellum and shelflike back of its head. Those characters, plus the presence of arolia and the fewer teeth on the mandible should distinguish Anthidiellum from Anthidium. These genera can be

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confused with Trachusa, because both genera are larger bees, but Anthidium have five or more teeth, while Trachusa have fewer than five teeth.

— Anthidium maculosum SIZE: Small to medium; 8.5–13.1 mm. PHENOLOGY: Mostly summer months; June through September with some records as early as February and as late as November. FLORAL HOSTS: Generalist. RANGE: California east to Texas, north to Oregon, Utah, and Colorado. NESTING: Twig nester, separating cells with pebbles, wood shavings, chewed up pieces of plant, and lizard feces. IDENTIFICATION: Midsized yellow-and-black bee, notable for the yellow “polka dots” on the abdomen. Males will conspicuously establish territories near plants that females visit. HEAD: On the frons, the pits are sparse, against a dull background. Few hairs appear on the face. In females, the clypeus is mostly dark, with small yellow patches laterally. Also in females, the mandible usually has seven teeth. In males, the apex of the clypeus is straight, with no notches. THORAX: Covered thinly with short white hairs. The thorax is yellow and black. Small yellow spots occur on the scutellum and metanotum, laterally. LEGS: On the hind tibiae there is a carina running the entire length of the back (anterior side). This can be difficult to

Anthidium maculosum (female)

Numerous yellow spots near the apex of each tergal segment

Anthidium maculosum (male) T7 has fingerlike lobes.

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see. In females, the fore and mid basitarsi are densely covered with white hair. ABDOMEN: The abdomen is dark, but with numerous distinctive yellow spots near the apex of each tergal segment. The tergal segments end with an impunctate margin, paper thin, and flaring out slightly. In females, T6 has a small indentation at its apical margin, and there is a tooth, laterally. In males, T7 has fingerlike lateral lobes. SIMILAR SPECIES: This is the most common species to have the carinate hind tibiae and the dull, sparsely pitted frons. A few species appear similar in these regards (A. chamelense, A. rodriguezi, and A. parkeri), but these species are larger and have fewer yellow spots on the abdomen.

— Anthidium manicatum SIZE:

Medium to large; 10–18 mm. May through October; multivoltine. FLORAL HOSTS: Generalist, some preference for flowers with long corollas and blue petals. RANGE: Not native to North America; found naturally in Europe. Now occurring from coast to coast in the U.S. and Canada. Most common in urban areas. NESTING: Cavity nester, usually high above the ground. Anthidium manicatum is invasive in the Western Hemisphere (see also A. oblongatum). It arrived in the U.S. in the early 1960s, but it has made its way to the West Coast in the last 50 years and is now widespread throughout North America. This bee (primarily the male) is extremely aggressive toward other insects when defending its territory and will attack and kill offenders. There are five spines on the lower tergal segments that it uses to pierce the PHENOLOGY:

Anthidium manicatum (female)

The bottom of the clypeus in females has small uneven bumps.

The basitarsi, especially the fore and mid, are covered in thick woolly hairs.

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exoskeleton of other insects, and it can damage other bees so severely that they can’t fly. There is some concern that it diminishes both floral resource availability for other pollinators in the areas where males have established territories, Anthidium manicatum has as well as seed set of those same floral resources. huge spines projecting from IDENTIFICATION: Strong black-and-yellow species T7; these are sometimes visible even while the bee is in flight. with males much larger than females. Most notable, the yellow stripes running across From the sides of each tergite there is a each tergal segment of the abdomen are swollen projection; on T6, there are broken up in the middle and form the actual spines. overall impression of a black V down the middle of the abdomen. HEAD: In females, Anthidium manicatum the apical margin of the clypeus has (male) numerous small uneven bumps across its length. LEGS: The basitarsi are covered in dense white fuzz, and on the hind tibia, there is a notable The pattern of black on strong ridge running its length. the abdomen resembles a V, and is distinctive among ABDOMEN: In males, T2–T5 bulge at the sides, North American Anthidium. and T7 has strongly curved spinelike projections. In addition, male tergal segments have copious curved hairs sprouting from the sides. SIMILAR SPECIES: This is the biggest of the Anthidium, and the most insufferable, seen very commonly in urban areas of North America. Despite its attitude, it is possible to mistake it for other species of Anthidium. The most notable features are the large spines and the end of the abdomen in males, which is not as prominent in most other Anthidium.

— Anthidium mormonum SIZE: Small

to medium; 7.7–13 mm. through August. FLORAL HOSTS: Generalist. RANGE: Widespread throughout the West, Pacific Coast east to New Mexico, and north to South Dakota. NESTING: Twig nester, uses plant trichomes to create cell walls. IDENTIFICATION: Yellow-and-black bees with light, sparse hair. HEAD: The clypeus and mandibles are yellow, as is the area between the clypeus and the inner margins of the compound eye. This ends at or above the level of the antennae. There are yellow spots to each side of the vertex, behind the compound eyes. In females, the mandible has five or six teeth. Though hard to see without a specimen, the labrum has two projections that PHENOLOGY: May

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curve upward. THORAX: Black, with thick tawny hair. Posterior-facing part of the propodeum dull, not shiny, with lines that appear almost scalelike. LEGS: Legs are yellow, fading to red brown at the apex. Thin sparse hairs cover the outer surfaces of the fore and mid basitarsi; the integument can clearly be seen through the hairs. There is no strong carina on the hind tibia. ABDOMEN: The abdomen has strong yellow bands, barely interrupted at the center, and wider at the sides. In males, these yellow bands run across the middle of each tergal segment, and the margins are wavy. The apical margin of each tergal segment is densely pitted, not shiny, and not very Strong yellow bands thin (pits become sparser near on the abdomen, barely interrupted the base of each segment). at the center In females, T6 has two small angles at the sides, and a small notch at the center. Scopal hairs are ivory colored. In males, T6 has two small teeth on the side; T7 is lobed to the sides, with a thin, parallel-sided, fingerlike projection in the center. Anthidium mormonum (female) SIMILAR SPECIES: This is a highly variable species and may be difficult to identify without reference material (and, in males, dissecting the genitalia). Nonetheless it is a common species and frequently seen. Anthidium mormonum may look most similar to Ivory-colored A. utahense, though that scopa species is slightly smaller.

Anthidium mormonum (male) T6 has 2 small teeth on the sides

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T7 is lobed with a thin projection in the center.

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In A. utahense, the propodeum is much more polished. In females, T6 has no lateral lobes. And in males, the lateral lobes are so broad, they extend almost to the center of the segment.

DIANTHIDIUM — SUBFAMILY: Megachilinae — TRIBE: Anthidiini OVERVIEW: Small black-and-yellow bees commonly seen hovering in front of flowers, especially Asteraceae. Most common in the summer. The genus includes both generalist and specialist species. Most species construct nests out of gravel or pebbles stuck together with mud and resin, and placed on branches or twigs, but a few groundnesting species also occur. May also nest in beetle burrows or preexisting holes in the ground. IN THE WORLD: Approximately 30 species in the world, found throughout North and Central America (many Mexican species). In the U.S. and Canada there are 23 species, all of which occur in the West or Midwest. CLEPTOPARASITES: Unknown, maybe Stelis. IDENTIFYING FEATURES: Small black-and-yellow bees. HEAD: The back edge of the head is a carina. In females, the mandible has three teeth. The subantennal suture runs straight between the antennal socket and the epistomal suture. THORAX: Posterior end of the metanotum has soft thick patches of hair on either side. The pronotal lobes are paper thin, and almost see-through, extending anteriorly, toward the head. The front-facing and side surfaces of the thorax (the omaulus) are also separated by a carina. WINGS: Two submarginal cells. LEGS: Arolia between front tarsal claws. ABDOMEN: In females, scopae are on the underside of the abdomen. SIMILAR GENERA: With their yellow-and-black markings, Dianthidium look similar to other Anthidiini, though they are the only ones with the distinctive thin margin on the pronotal lobes. They can be distinguished from Anthidium by the teeth: Anthidium have five teeth, while Dianthidium have three teeth; also, Anthidium are generally larger. Anthidiellum are more similarly sized but have four teeth and curved subantennal sutures. Trachusa lack the paper-thin pronotal lobes seen in Dianthidium as well as the sharp edges at the back of the head, and between the front and side of the thorax. In Paranthidium the front and middle tibiae are significantly modified so that there is a shallow, polished depression (see Paranthidium for more details).

— Dianthidium curvatum SIZE: Small; 7 mm. PHENOLOGY: April through October. FLORAL HOSTS: Has a preference for flowers in the Asteraceae. RANGE: This is the most commonly seen of the western Dianthidium. Texas west to California, north through the Pacific Northwest. NESTING: Nests in dense aggregations in the soil, with nest cells often attached to plant roots. Occasional nests are in vertical banks. D. curvatum uses sand grains, held together by

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plant resin to construct nest chambers. Species may share nest entrances, but not nest chambers. IDENTIFICATION: Small yellow-and-black bee. HEAD: In both sexes, the clypeus is usually yellow, but some female specimens have yellow only on the sides of the clypeus. Yellow markings continue up the sides of the face, but end abruptly at the top of the compound eyes. Mandibles are entirely black, with three teeth in both sexes. The There is yellow at the top of the scutum, to either side of center. The yellow extends lateral ocelli are small compared all the way to the sides of the scutum, and is not just a little yellow spot. with those of other Dianthidium species. THORAX: Maculations on the front half of the scutum are variable; may be all black, or with a line of yellow at the anterior margin extending to the sides. The axillae and the scutellum are yellow. WINGS: Smoky. LEGS: In both sexes, the forecoxa has a short Legs are yellow The edge dividing the front but distinct spine at the apex. in this species. and side faces of the side of the thorax is sharp. ABDOMEN: Tergal segments have yellow spots on the sides, separated Dianthidium curvatum (female) by black in the middle. In males T6 may have significant yellow or red markings, or may be entirely black. Even from above, the paper-thin, translucent SIMILAR SPECIES: Dianthidium pronotal lobes are evident (true of all Dianthidium). curvatum individuals are

The yellow markings on the face are thick lines running up beside each eye. Dianthidium curvatum (male)

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distinctive for their predominantly red-brown coloring on the thorax and legs, and for the spine on the forecoxa. In the West there are two subspecies. Dianthidium curvatum sayi has red-brown markings with yellow on the head. Dianthidium curvatum xerophilum, which occurs only in the Southwest, has less red brown on the head.

— Dianthidium pudicum SIZE: Small; 8–10 mm. PHENOLOGY: June through August. FLORAL HOSTS: Generalist. RANGE: Widespread throughout the West and Midwest; southern Canada through southern California and New Mexico. East to South Dakota. NESTING: Nests in forks of trees, in nests made of resin, pebbles, and large grains of sand. IDENTIFICATION: Small, uncommonly seen yellow-and-black bee. HEAD: Yellow extending sideways to the inner margins of the compound eyes, and up the face. The area between the antennal sockets is flat, with some yellow. On the vertex, there are two yellow spots to either side, and on the gena. Above the clypeus punctures are dense, but the area between them is polished. Clypeus black or yellow. In females, the mandible is missing a preapical tooth, or it is so small that the top edge looks straight. THORAX: Pronotal lobes are yellow, and there are yellow spots on the anterior margin

Dianthidum pudicum (female)

The paper-thin pronotal lobes found in Dianthidium are obvious here.

Dianthidum pudicum (male)

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of the scutum. Yellow outlines the posterior margin of the scutellum. Tegulae are yellow. LEGS: Mostly yellow, tarsal segments brown. ABDOMEN: In females, T1 is mostly black. Yellow intermittent stripes run across each segment, with notches of black on the posterior margin of the yellow. In males T7 has three lobes, with the middle lobe long and curved slightly in, extending past the two lateral lobes. The sixth sternal segment is gently rounded. SIMILAR SPECIES: There are two subspecies of D. pudicum. Dianthidium pudicum pudicum has lighter, almost ivory marks on the thorax and abdomen. Dianthidium pudicum consimile has darker yellow markings.

— Dianthidium ulkei SIZE: Small; 8–10 mm. PHENOLOGY: June through August. FLORAL HOSTS: Generalist. RANGE: Pacific Coast east to Nebraska and Texas, north to southern British Columbia. NESTING: Twig-nesting species. IDENTIFICATION: Small yellow-and-black species. HEAD: Yellow can variably cover all of clypeus, or it may be interrupted in the center but extensive on the sides near the compound eyes. Near the middle simple eye, there is a yellow mark. The area between pits is dull. In females, the mandibles have yellow markings. THORAX: Densely pitted; pits on the scutum are about the same size as those on the scutellum. On the side of the body, there is a large yellow mark, bigger than the mark on the pronotal lobes. ABDOMEN: The sixth tergal segment is all black. The first tergal segment is black, but with yellow spots at the center and to the sides. SIMILAR SPECIES: There are several subspecies of D. ulkei, but they grade into each other so completely that it can be difficult to distinguish them from each other. Dianthidium ulkei males look very similar to D. platyurum; males can be identified

Dianthidium ulkei (female)

Dianthidium ulkei (male)

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only by using characters on the genitalia. With females, D. platyurum appears shinier on the face in between pits, and the mandibles are completely black.

PARANTHIDIUM — SUBFAMILY: Megachilinae — TRIBE: Anthidiini OVERVIEW: Small yellow-and-black bees, seen in midsummer as they collect pollen from the Asteraceae on which they specialize. Nest in the ground, often in sandy soil. May nest in small aggregations of a dozen or so individuals. IN THE WORLD: Worldwide there are seven species, all in North and Central America. In the U.S. and Canada there is one species with three subspecies: P. j. perpictum occurs in Colorado, New Mexico, and Arizona; P. j. butleri is found only in Arizona; and P. j. jugatorium occurs in the Midwest. CLEPTOPARASITES: Unknown, maybe Stelis. IDENTIFYING FEATURES: HEAD: The mandible has three or four teeth, but not five. In females, the mandible is broad at the base, and extremely narrow at the beginning. THORAX: The propodeal triangle is extraordinarily punctate. WINGS: Two submarginal cells. LEGS: There is an arolium; on the fore- and midtibiae there is no tibial spine arising from the end (apex) of the tibia. Instead, the outer apical tibial margin is gently curved, creating the edge of a spoonlike indentation that runs along the tibia. ABDOMEN: In males, T7 has three lobes, with the middle lobe longer and broader than the ones on either side. In females, scopae are on the underside of the abdomen. SIMILAR GENERA: Dianthidium look very similar to Paranthidium. The carina that is so evident at the back of the head in Dianthidium, however, is lacking in Paranthidium. In addition, while both genera have thin projections (lamellae) extending forward from the pronotal lobe, they are very short in Paranthidium, as opposed to the more obvious projections of Dianthidium. The shape of the fore- and midtibiae in Paranthidium is distinctive; it is rounded and scooplike, which is not the case for any other Anthidiini in western North America.

— Paranthidium jugatorium SIZE: Small; 8–9 mm. PHENOLOGY: Late summer, July through early September. FLORAL HOSTS: Appears to specialize on Asteraceae. RANGE: The mountains of New Mexico and Arizona north through Colorado and Utah. NESTING: Holes in the ground, may make its own in sandy soil, or may use preexisting, including old nest burrows of other bee species. Pebbles are brought to the nest and used to form mini scree slopes that separate nest cells. Very little resin is used.

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p

Paranthidium  221 No strong ridge separates the top of the head from the rear of the head (as in Dianthidium).

Paranthidium jugatorium (female)

While not entirely unique to Paranthidium, the dip in the yellow markings of the abdomen is a hint as to this bee’s identity.

Paranthidium jugatorium (male)

The pronotal lobe is paper thin, but does not extend out past the thorax at all. The tibia is curved, and almost scoop-shaped on the inside (not seen here). There is no apical tibial spine.

IDENTIFICATION: Striking yellow-and-black bee with yellow bands running across each abdominal segment. Bands are separated in the middle by black, but the width of the black diminishes toward the apex of the abdomen. As this is the only species in the western U.S., other characters are included in the genus description above. SIMILAR SPECIES: There is only one species of Paranthidium in the U.S. For similar genera, see above.

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222  Megachilidae

STELIS — SUBFAMILY: Megachilinae — TRIBE: Anthidiini OVERVIEW: Stelis are uncommon small to medium-sized bees with variable coloration ranging from jet black to dark with yellow-and-orange-striped abdomens. These bees are cleptoparasites on a wide array of other megachilid genera. When a host bee is away from the nest, a female Stelis enters the nest and deposits one or two eggs on the pollen mass left by the host for her own offspring. The Stelis larva kills the host bee’s offspring and then eats the pollen. IN THE WORLD: Worldwide there more than 100 species; the majority are found in the Northern Hemisphere. In the U.S. and Canada there are 51 species, with the majority occurring in the West (more than 40 species). IDENTIFYING FEATURES: Rounded dark bees, often with dark yellow, cream, or orange markings on the face, edges of the thorax, and abdomen. Like all other Megachilidae, they have two submarginal cells, though as a cleptoparasite, they lack pollen-collecting hairs on their abdomen or anywhere else. HEAD: The preoccipital ridge is rounded, not carinate. THORAX: The scutum and the surface of the tergal segments on the abdomen both appear extremely roughened with thick, dense punctures. WINGS: The second recurrent vein meets the submarginal cells behind the vein defining the second submarginal cell. LEGS: There is an arolium between the tarsal claws, which are cleft. On the midtibia, there are two spines at the apex (tip). ABDOMEN: In males, there are no spines or protrusions at the apex. SIMILAR GENERA: The body shape of Stelis appears similar to Osmia or some other Osmiini. Look for yellow or ivory markings, especially on the abdomen, the roughened integument, and the cleft tarsal claws (which are not split in Osmiini). Since Stelis is in the tribe Anthidiini, species can appear similar to others in that group. There are no carinae, ridges, or lamellae that stand out on Stelis, as is seen in other Anthidiini that have an arolium between the tarsal claws. Distinguishing between species of Stelis is difficult, involving minute characters that grade into each other. Furthermore, there is no modern key for western species; species identifications should be verified against a reference collection or by an expert. We do not provide similar species for the two species included here, because many that look similar do not yet have published names.

— Stelis laticincta SIZE: Small; 8–9 mm. PHENOLOGY: June through August. FLORAL HOSTS: Cleptoparasite; no floral preferences. RANGE: California north to Washington, east to Nevada and Arizona. NESTING: Cleptoparasite of Megachile. IDENTIFICATION: Rare cleptoparasite of Megachile. HEAD: Clypeus yellow, and with yellow stripe running next to each compound eye. THORAX: Heavily and coarsely pitted, very slight metallic. Scutum is lined on the anterior and lateral sides with a thick yellow stripe. The posterior margin of the scutellum is also lined in yellow.

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Stelis  223 WINGS: Long,

dusky along top margin. numerous pits. Broad yellow bands run across each segment, sometimes very slightly notched at the center. ABDOMEN: Deep,

Stelis laticincta (female)

Stelis laticincta (male)

— Stelis perpulchra SIZE: Small; 5–9 mm. PHENOLOGY: April through June. FLORAL HOSTS: Cleptoparasite; no floral preferences. RANGE: Southern California east to New Mexico and western Texas, north to Utah, Colorado, and Nevada. NESTING: Parasitizes small Osmiini, most of which nest in preexisting cavities. IDENTIFICATION: Rare, small black-and-yellow bee. HEAD: Yellow running vertically next to each compound eye. THORAX: Polished with deep, sparse pits. Pronotum lined in yellow. Posterior margin of scutellum also lined with

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224  Megachilidae

yellow. WINGS: Long, tips dusky, near marginal cell. ABDOMEN: Polished with slightly metallic tint. Apical margin of T1 with yellow, interrupted at the center. Tergal segments 2–4 with yellow spots near the margin, one to either side of center, and two near the lateral margins.

Stelis perpulchra (female)

Stelis perpulchra (male)

TRACHUSA — SUBFAMILY: Megachilinae — TRIBE: Anthidiini OVERVIEW: Robust bees, often large, not always as yellow and black as some of the other Anthidiini, though more so than other Megachilidae. May be slightly hairy. The dietary preferences for most species are unknown, but some appear to be specialists. Ground nesters. Inside nests, cells are separated using either leaf material, resin, pebbles, or soil. Occasionally nest in aggregations. IN THE WORLD: With more than 50 species worldwide, Trachusa can be found throughout the Northern Hemisphere. A few species also occur in Africa. There are 19 species in North America, with 12 occurring west of the Mississippi river. CLEPTOPARASITES: Stelis and Coelioxys. IDENTIFYING FEATURES: Large anthidiine. HEAD: The head rounds gently from top to back, with no carina separating the faces. The head is thick, with the ocelli near the middle of the top of the head, rather than the back. In males, there are yellow markings on the clypeus and usually beside each compound eye. WINGS: The second recurrent vein comes very close to meeting the second submarginal vein straight on. There are two submarginal cells. LEGS: The midtibia is wide, nearly as wide as the hind tibia, convex on

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Trachusa  225

both the front and back, and often with a blunt projection on the front tibia, rather than a ridge or spine. The hind tibia has small bumps covering its surface. The tarsal claws are split so that there are two teeth. There is an arolium, but it is much smaller than in many similarly black-and-yellow genera. ABDOMEN: The anterior face of T1 has a ridge where it folds to the dorsal face, creating a concave surface. There is no pygidial plate. In males, the final tergal segment curls strongly under, so that it is difficult to see. In females, pollen is collected on the underside of the abdomen. SIMILAR GENERA: Trachusa look similar to other anthidiines, including Anthidium, Dianthidium, and Paranthidium. The larger size is a clue, as is the lack of projections, lamellae, or ridges on the body. The midtibia, though not the easiest body part to see, is distinct in Trachusa, being relatively wide and convex both posteriorly and anteriorly.

— Trachusa larreae SIZE: Medium; 10–12 mm. PHENOLOGY: April through July. FLORAL HOSTS: Specialist on Larrea tridentata (creosote bush). RANGE: Southwest deserts where L. tridentata occurs; Texas west to southeastern California, north to Utah, southern Nevada. NESTING: Nests in large aggregations; inside nests, cells are made of resin collected from creosote bush, collected in a ball that the female carries behind her mandibles, using her labrum. The resin is thought to be antifungal, antimicrobial, and unpalatable to most predators. IDENTIFICATION: Larger mostly yellow bee seen on Larrea in the spring. HEAD: Heavily marked with yellow, including all of the clypeus, the gena, the vertex, and the paraocular areas. THORAX: Dorsal surface of thorax outlined in yellow, often with additional yellow as two lines running the Trachusa larreae length of the scutum. LEGS: The (female) outer surfaces of the tibiae with short, pale, stout hairs (not scopal hairs). ABDOMEN: The dorsal surface of T1 is yellow, and broad yellow bands run across each of the following tergal segments, uninterrupted except slightly at the sides. In females, T6 is flat when viewed from the side, and slightly notched when viewed from above.

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226  Megachilidae

In males T7 is heavily notched at its center and is overhung by T6. SIMILAR SPECIES:

Trachusa larreae is one of the easier Trachusa to identify because of the heavy yellow markings on the body, and its association with creosote bush. Males can additionally be recognized by the missing apical projection at the apex of T7 (seen in most of the other western yellow Trachusa species). In females, the long thin lines on the scutum, the yellow clypeus, and the unmodified terminal tergal segments are telling.

Trachusa larreae (female)

Trachusa larreae (male)

— Trachusa perdita SIZE: Medium; 11–13 mm. PHENOLOGY: May through June. FLORAL HOSTS: Appears to be a generalist. RANGE: Restricted to California, most commonly along the coastal mountain ranges. NESTING: Nests in sandy hillsides, often in aggregations. Cells are lined with thick leaf pieces, cemented together with plant resin. IDENTIFICATION: Robust, ruddy bee with red hair on thorax and striking white bands on black abdomen. HEAD: In males, clypeus is ivory, with markings running beside the compound eyes as well. Also in males, the mandibles are black, and the apical (innermost) tooth is broad and short, so that the second and third teeth are closer together than the second is to the apical tooth. THORAX: Covered in thick, short, rust-red hair. LEGS: Thin, short, white hairs coat the outer surfaces of the leg segments. ABDOMEN: Thin white bands run across the apex of each tergal segment. There are no yellow markings. In females, T6 with strong raised area at the base forming an overhang before the apex of the segment. In males, T6 has a keel that ends just before the apex, and the apex is evenly rounded.

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Lithurgopsis  227

Trachusa perdita (female)

SIMILAR SPECIES: Few similar-looking Trachusa overlap with the range of this species. In the area, it is most similar to T. gummifera, though in that species, males are missing the facial markings next to the eyes (or they are minimal), and markings on the clypeus are restricted to the apical half. In females, T6 of T. gummifera does not have the median projection that is so evident at the center of Trachusa perdita (male) T6 in T. perdita.

LITHURGOPSIS — SUBFAMILY: Lithurginae — TRIBE: Lithurgini OVERVIEW: Large dark bees with oversized heads, usually seen deep inside cactus blossoms. Mostly late spring through summer bees. North American species collect pollen only from cactus flowers; the closely related nonnative species Lithurgus chrysurus collects pollen from the also nonnative star thistle (Centaurea), which is from the Mediterranean. All Lithurgopsis nest in wood, often dead wood. IN THE WORLD: Worldwide there are roughly 10 species of Lithurgopsis, all of which occur in North and South America. The closely related genus Lithurgus, with 36 species, is more widely distributed, around the world. There are six species found in the U.S. and Canada. CLEPTOPARASITES: No known bee parasites. IDENTIFYING FEATURES: Large solid black bee with light white stripes on abdomen; appears slightly elongate. HEAD: In females, there is a strong protuberance between the

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228  Megachilidae

antennal sockets, entirely above the clypeus. From a distance this looks like a black bald spot above the clypeus; up close the 3-D nature of the structure is evident. First flagellar segment shorter than second flagellar segment. WINGS: Two submarginal cells. LEGS: On the hind tibia there are coarse tubercles. The hind tibial spur is strongly bent at its tip. In males, there is an arolium. ABDOMEN: Females have a central spine in place of a pygidial plate; scopal hairs are on the sternal segments of the abdomen. In males, on the abdomen, there is a well-developed pygidial plate. SIMILAR GENERA: Megachile look similar but lack the protuberance on the face in females. In males, the spinelike pygidial plate seen in Lithurgopsis is unique. Lithurgus can be hard to distinguish from Lithurgopsis. The arolia seen in male Lithurgopsis are absent in Lithurgus. And in females, the protuberance on the face includes the clypeus as well as the area above it in Lithurgus, but not in Lithurgopsis.

— Lithurgopsis apicalis SIZE: Medium; 10 mm. PHENOLOGY: May through July. FLORAL HOSTS: Specialist on Cactaceae, especially Opuntia, but also Echinocactus, Cylindropuntia, Sclerocactus, and others. RANGE: Western Texas, west through Utah, Nevada, and southern California. North to Wyoming and South Dakota. NESTING: Nests in dead wood, and in the stalks of dead or dying flower stalks of Agave. IDENTIFICATION: Larger bee, commonly seen in cactus flowers. Usually has a red tip on the abdomen. HEAD: Slightly longer than wide, and with many modifications in both sexes. In females, the supraclypeal area is modified into two protrusions, each formed in the shape of a horizontal comma. There are few punctures on the polished clypeus. In the malar space, there is a deep and distinct depression or pit. In males, the supraclypeal area is gently shaped like a C. On the clypeus, there is a ridge, just above the lower margin of the mandible. In males, there are no tubercles on the labrum (this is hard to see). THORAX: Black, with some white hair, but not dense. Scutum densely but evenly pitted. LEGS: Brown. ABDOMEN: Each tergal segment has an apical hair band of soft white hairs, slightly thinner at the center than along the edges. In females, T5 is often covered in thick long reddish hairs, visible even as the bee roots in a flower for pollen or nectar. Also in females, scopal hairs are reddish. SIMILAR SPECIES: Lithurgopsis apicalis appears similar to L. littoralis. The shape of the protrusions above the clypeus is distinguishing; in L. littoralis, the elevated ridge runs vertically, being interrupted at its center. In L. apicalis, the two protrusions appear to run vertically, up each side of the face just beside (and below) the antennal sockets. Also, in L. littoralis, the ridge just above the lower margin of the clypeus, seen in L. apicalis, is missing. In males, there are two tubercles on the labrum of L. littoralis, while L. apicalis does not have any tubercles on the labrum.

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Lithurgopsis  229 Two protrusions in the supraclypeal area

Lithurgopsis apicalis (female)

Lithurgopsis apicalis (male)

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230  Apidae

APIDAE

Apidae is a family of extremes and contrasts. For example, while it is one of the most diverse families in North America and includes many of our most recognizable bees, it also includes its share of seldom-seen genera as well. And while many Apidae are large and fuzzy and fast fliers, there are subfamilies that are small and nearly hairless. Bees in the family Apidae span the spectrum of behaviors from highly social species with a queen, workers, and clear division of labor, to completely solitary species. Apidae also contains the largest proportion of cleptoparasitic species of any family. There are more than 5,700 species and 200 genera in the world, and they occur on every continent. In North America there are more than 1,000 species in 50 genera. The vast majority of North American Apidae nest in the ground, though a few, like the carpenter bees, nest in wood. Among North American species are a large proportion of specialists as well as many generalists. While not native to North America, the most famous and recognized species in the family is undoubtedly Apis mellifera (the western, or European, honey bee). This introduced species lives in large hives with tens of thousands of workers, which maintain the hive all year long, living on honey stores when flowers are not in bloom. They are also the only species with barbed stingers, which means workers often die after stinging. The honey bee is the only bee species in the U.S. and Canada to make honey. The honey bee has become a key player in many intensive agricultural systems as it is often used for orchard and crop pollination and is increasingly being introduced into cities by urban beekeepers. Also found in the Apidae are squash bees, carpenter bees, bumble bees, digger bees, and long-horned bees. IDENTIFICATION: Because the family is so diverse, unifying characters are not immediately evident. It is often easier to identify the genus than the family. Many of the characteristics used to identify members of Apidae are small differences in specific parts of the mouth. These can be hard to see. All bees in the family Apidae have a long tongue. While not true for all genera, most are very hairy, and females often have dense, very long scopal hairs on their hind legs. Larger species also often have a reduced jugal lobe. 1 TAXONOMY: Worldwide there are nearly 6,000 species in the family Apidae, distributed on every continent and 2 species-rich wherever they occur. In North America there are around 1,000 species, 3 4 divided among three subfamilies (these three subfamilies are the only subfamilies in Apidae around the In long-tongued bees, like those in Apidae, the first world), and numerous tribes: Apinae, two segments of the labial palps are elongated and primarily the medium to large-sized are much longer than the second two segments.

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APIDAE  231

fuzzy bees; Nomadinae, comprising entirely cleptoparasites; and Xylocopinae, the small and large carpenter bees. Details for the subfamilies are listed below.

—  SUBFAMILY XYLOCOPINAE There are two genera, each in its own tribe in this subfamily. In the tribe Xylocopini are Xylocopa, large, shiny, black bees. In the tribe Ceratinini are the significantly smaller but also shiny Ceratina. See the text below for more characteristics.

—  SUBFAMILY APINAE There are 26 genera in this subfamily in North America; 23 of them occur in the West or Midwest. While there is considerable morphologic diversity in the look of the Apinae, almost all females have slender hairs along the apical margin of S6 that get denser toward the center. In many groups the clypeus protrudes markedly from the face. In non-cleptoparasitic tribes, the pygidial plate, pygidial fimbriae, and prepygidial fimbriae are present. Scopal hairs are restricted to the hind tibia and basitarsus. — ANTHOPHORINI: All are robust bees, fast-flying, with copious hair. On the wings there are no hairs, so that the cells are completely bare. This group consists of two genera, Habropoda and Anthophora. — APINI: While the Apini are well represented in other parts of the world, in North America this tribe is represented by just one species: Apis mellifera. It can be distinguished from other Apidae (and Apinae) by the corbicula in females and the hairy compound eyes. On the hindwing, there is a jugal lobe. — BOMBINI: The Bombini are represented by one genus in North America, Bombus, which also contains the subgenus Psithyrus, the cleptoparasitic bumble bees. Bombus and Apis are the only corbiculate Apidae; but Bombus have no jugal lobe, and their compound eyes are not hairy. — CENTRIDINI: Large, bold bees that fly fast and are hairy. On the head, the first flagellar segment is often longer than the scape. On the wing, there is only a very small stigma. On the legs, there is no arolium (seen commonly in many Apidae). There is one genus in North America: Centris. — EMPHORINI: Medium to large bees, with lots of hair. In males, the antennae are short. On the head in both sexes, the vertex is gently curved, and stands out above the ocelli. This tribe is found only in the Americas. There are four genera. In the West, Diadasia dominate, but Ancyloscelis are also present in the desert Southwest. Ptilothrix, which is common in the East, occurs in the West just at the border with Mexico (it is not highlighted in this book). In the East, Melitoma can also be found (not in this book). — ERICROCIDINI: Medium to large strikingly patterned cleptoparasites. These bees are cleptoparasites of Centris. Ericrocis is the most common genus. A second, Mesoplia, occurs very rarely in southern Arizona (not in this book).

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232  Apidae

— EUCERINI: Medium to large hairy bees, usually with pale hair bands. In males of many species the antennae are very long. On the tongue, if it can be seen, the paraglossa is very long, often reaching to the end of the second segment of the labial palpus. On the head, the vertex is flat, so that the ocelli poke up a little. In North America there are 212 species in 14 genera. All but one genus (Florilegus) can be found in the West. The diverse genus Eucera includes several subgenera that used to be separate genera: Cemolobus, Eucera sensu strictu, Peponapis, Tetraloniella, Syntrichalonia, Xenoglossodes, and Xenoglossa. Tetraloniella has been combined under Xenoglossodes and no longer exists. Other genera include Svastra, Melissodes, Martinapis, Gaesischia, Melissoptila, and Simanthedon; these last three are not included in this book. — EUGLOSSINI: These are the orchid bees, rarely seen even in their native range. The species here have extraordinarily long proboscises and brilliant green bodies. There is one genus in North America: Euglossa. — EXOMALOPSINI: Small to moderately sized hairy bees with pale hair bands on the abdomen. On the head, next to each compound eye, there is a row of long, stout hairs, which is not seen in other Apidae genera. This group consists of Exomalopsis and Anthophorula, both of which only occur in the West. — MELECTINI: Strikingly colored cleptoparasitic bees. Larger than many other cleptoparasites, and also fuzzier. In North America there are three genera: Brachymelecta, Melecta, and Zacosmia. — OSIRINI: Includes one North American genus, Epeoloides. There are two species of Epeoloides, one in Europe and one in the U.S. and Canada, which has only been seen a handful of times. It is not included in this book. — PROTEPEOLINI: Includes one North American genus, Leiopodus, which occurs only along the border of Mexico with the U.S. It is not included here.

—  SUBFAMILY NOMADINAE All bees in this subfamily are cleptoparasites, lacking scopal hairs, and often with patches of appressed hairs on the thorax and abdomen. Many of these tribes have in them only one genus. With a few exceptions, most are rarely seen. — AMMOBATINI: In North America, represented by one genus, Oreopasites. — AMMOBATOIDINI: Consists of one genus in North America, Holcopasites. — BIASTINI: Two genera of very small bees, Neopasites and Rhopalolemma. Neither is featured in this book.

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Xylocopa  233

— BRACHYNOMADINI: A tribe better represented in South America; in North America, three genera occur in the Southwest: Brachynomada, Paranomada, and Triopasites. None of these is featured in this book. — EPEOLINI: Stout, strikingly marked, black-and-white bees with pointed abdomens. The axillae are elongated into points that hang over the scutellum. Two genera: Epeolus and Triepeolus. — HEXEPEOLINI: Consists of one genus, Hexepeolus, found only in the southwestern U.S. Not in this book. — NEOLARRINI: Only one genus of very small bees, found in the western U.S.: Neolarra. — NOMADINI: Only one genus, Nomada. Unlike other genera included in the Nomadinae, Nomada are relatively common. They are slender, wasplike, often with thickened antennae. Colors include some combination of red, white, yellow, and black. — TOWNSENDIELLINI: Contains one genus of black-and-white bees, Townsendiella, found only in arid areas of the western U.S.

XYLOCOPA — SUBFAMILY: Xylocopinae — TRIBE: Xylocopini OVERVIEW: Species in this genus are among the largest in North America. With shiny black bodies, loud wings, discourteous behavior, and a propensity for nesting communally in wood close to humans, they are hard to miss. Carpenter bees can be seen from March through October; one of the few bees with adults that can overwinter. They are generalists that prefer large open flowers but will “steal” nectar from those with narrow corollas by cutting a hole at the base of the flower to get to it. Nest in dead wood, especially tree stumps; one of the few bees to chew their own holes. Often nest in gables, soffits, gazebos, decks, and other wood structures near homes. Nests are long galleries, used for multiple generations, but elongated each year to accommodate new members. IN THE WORLD: More than 400 species worldwide, well represented on every continent. In the U.S. and Canada there are nine species, seven of which occur in the West. CLEPTOPARASITES: No bee parasites known. IDENTIFYING FEATURES: Large, shiny black to bluish-black bees. Easy to recognize. HEAD: In males, the lower half of the face has bright yellow markings. The head overall is round—wider than long or subequal; the malar space is very short. THORAX: In North American species, the thorax of both males and females is often covered with dense hair, either black or auburn. WINGS: The marginal cell is very elongated, tapering to a point at both ends. The second submarginal cell is narrowed, almost triangular in shape, with the margin closest to the marginal cell much narrower than the bottom margin.

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234  Apidae LEGS: In females, scopal hairs are stiff stout brushes of black hair. ABDOMEN: Relatively hairless, and those hairs present are dark. SIMILAR GENERA: Bumble bees (Bombus) are often mistaken for Xylocopa. The yellow integument on the faces of Xylocopa males distinguishes those individuals from bumble bees. And the shiny abdomen, lacking distinct hair bands, distinguishes them from female bumble bees, which have a hairy abdomen. In addition, bumble bees carry pollen in a shiny corbicula, whereas female Xylocopa have stout thick scopae on their hind legs. The head of the bumble bee is often longer than it is wide, whereas Xylocopa have very round heads. Male Xylocopa sonorina appear similar to Centris; however, X. sonorina males have yellow hair covering the abdomen, while Centris have black hair on the abdomen.

— Xylocopa californica SIZE: Large; 20–25 mm. PHENOLOGY: February through October, peaking in summer (June and July), and with a longer flight season at lower elevations and latitudes. FLORAL HOSTS: Generalist, visiting a wide array of flowers. RANGE: Widespread throughout the Southwest, rarely occurring as far north as Oregon, Montana, and Idaho, and east to Kansas and Louisiana. Absent from the central and northern Rocky Mountains. NESTING: Nests in Agave, cottonwood (Populus), and Yucca. IDENTIFICATION: Large black bee with metallic reflections, especially on abdomen. HEAD: Black round head. In females, large pit between

Xylocopa californica (female)

Metallic reflections, especially on the abdomen

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Pit between antennae (about the size of the antennal socket)

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Xylocopa  235

antennae (about the Xylocopa californica (male) size of the antennal sockets). In males the clypeus is usually dark (some local populations from southern Arizona have Metallic reflections, especially on the abdomen ivory on the clypeus). Also in males, the eyes are more or less parallel, not converging notably toward the top of the head. The antennae are black. THORAX: The thorax is black. WINGS: Dark smoky brown wings. LEGS: On the hind legs, the tibiae have short thick hairs. ABDOMEN: Dark, with strong metallic blue or green tints. In females, there are two rows of spines on T6 that diverge at the base of the tergal segment, so that they are almost at right angles to each other. Also on T6 is a flattened spine at the posterior margin. In males, T7 is rounded, without teeth. SIMILAR SPECIES: This is the most metallic of the common western species, and that combined with the hair patterns on the abdomen should distinguish this bee from other Xylocopa species. There are three subspecies, which can be distinguished largely by where they occur. Xylocopa californica californica is most common in North Coast ranges of California, the Sierra Nevada, and the southern Cascade Mountains of Oregon. The abdomen has a slight green tint, and there is a fringe of white hairs on T4 in females. Xylocopa californica arizonensis occurs in deserts from Arizona east to Texas. The wings are very dark, even slightly purple, and the abdomen is a deep blue. Xylocopa californica diamesa occurs in the low mountains and foothills of southern and central California. Its wings are paler, and the abdomen is a lighter blue green than any of the other subspecies.

— Xylocopa tabaniformis SIZE:

Large; 20–23 mm. through October, peaking in May and June. Multivoltine with at least two generations per year. Most active in the early morning and evening. FLORAL HOSTS: Generalist, visiting a wide array of flowers. RANGE: California and Oregon east to Texas and Colorado, usually higher elevations. Rare in the Great Basin, and absent from the Great Plains. NESTING: Often nests in aggregations. Prefers non-rotten wood, including PHENOLOGY: March

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redwood and cedar posts, in which it actively chews out tunnels that are 4–6 inches (10–15 cm) long. Chewing a new tunnel can take weeks for one individual. Can be problematic for carpenters and those with wood structures outside their homes. IDENTIFICATION: A small carpenter bee. HEAD: In females, head is black. In males, the lower portion of the face is yellow, including the clypeus, labrum, supraclypeal area, and paraocular area. THORAX: The thorax is covered predominantly in dark hair, though there may be some light hair anteriorly in males. WINGS: Lighter gray to brown wings. LEGS: There are no short thick hairs on the hind tibiae. ABDOMEN: The abdomen is black, and not metallic. Some dark hair covers the abdomen, and there may be a fringe of pale hairs at the apex of T2–T6 (especially T4) in some male subspecies. In females, there are two rows of nearly parallel spines on T6. In males, there are two sharp teeth on T7. Also in females, S1 has a notch at its center, though this will only be visible with a microscope. SIMILAR SPECIES: There are several subspecies of X. tabaniformis, with many of them occurring only in Mexico. Three subspecies are found north of the border: Abdomen black, not metallic Xylocopa tabaniformis orpifex, which occurs along the Pacific Coast, and in which the abdomen is covered entirely in dark These bees are so large T6 with that they often steal parallel spines nectar from the base of tubular flowers, rather than enter the corolla opening.

Xylocopa tabaniformis (female)

Lower portion of the face yellow Xylocopa tabaniformis (male)

T7 with two sharp teeth

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hair. Xylocopa tabaniformis androleuca, which occurs in Arizona, New Mexico, and the southern reaches and sky islands of the Great Basin, is indistinguishable from females of X. t. orpifex, except by location. Males of X. t. androleuca have pale hairs at the apex of T4 and T5, stronger on the sides, and interrupted at the middle, as well as some lighter hairs on the head and thorax. Xylocopa tabaniformis parkinsoniae occurs in southeastern Texas.

— Xylocopa sonorina SIZE: Large; 18–26 mm. Largest bee in North America. PHENOLOGY: February through November. FLORAL HOSTS: Generalist, visiting a wide array of flowers, with no apparent dislike of introduced plants or cultivars. RANGE: Common in urban settings. Oregon south to Baja (and into South America), east to Texas and Utah. Introduced to Hawaii. Found mostly in upland areas with deciduous trees. NESTING: Nests in deadwood, including fences, telephone poles, logs, furniture, and man-made wood structures. Holes are about the diameter of an index finger. IDENTIFICATION: Striking large bee, locally abundant but not as widespread as other species. Males and females look markedly different from each other. This species is very docile. HEAD: Face is round and flattened; clypeus does not protrude at all. In females, the head is black, and the mandible is bidentate. In males, the eyes are bright green and close to parallel. Also in males, the clypeus, frons, and paraocular areas of face are yellow, and there is a yellow Largest bee in North America

Xylocopa sonorina (female)

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Abdomen wider than the thorax; polished black but not metallic

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Males of several species of Xylocopa hover at the tops of trees in a “lek”, defending territories and attracting females with sex pheromones. The males fight with each other as they hover, and mate with females that fly up the tree, attracted by the scent.

Xylocopa sonorina (male)

Eyes are bright green in live specimens

line running the length of the antennal scape. THORAX: In females, solid black; the slightly domed scutum is covered with close pits on a smooth surface. In males, Large bee covered in blonde hair the thorax is covered in thick blonde hair, inflated, with reddish tegulae. WINGS: Dark, with a slight coppery or purple sheen. LEGS: Hairs on legs, including scopal hairs in females, entirely black, except on the foretarsi, where they are light red. In males, hairs on legs are blonde to red. Also in males, femur is inflated, and rather hairless. ABDOMEN: In both sexes the abdomen appears inflated, much wider than the thorax. In females, abdomen is black but not metallic, polished to shine. There are sparse hairs. The first sternal segment has a strong keel at its center, running parallel to the length of the body; this can be hard to see without a specimen in hand. In males, there are thick blonde hairs covering each tergal segment. SIMILAR SPECIES: Males are one of the more unique bees in western North America and hard to mistake with other Xylocopa species. In females, the large size and lack of metallic tints are helpful characteristics, as is the bidentate mandible.

CERATINA — SUBFAMILY: Xylocopinae — TRIBE: Ceratinini OVERVIEW: Small bees, but often extremely abundant. Shiny gunmetal green/black bodies, with white markings on the face. All species are generalists and can be seen on a wide variety of flowers, including weedy plant species. Ceratina nest in the pithy stems of last year’s flowering forbs and especially shrubs (Sumac, Sambucus, etc.). Females overwinter as adults in small tunnels in stems and excavate that same tunnel into a nest in the spring. IN THE WORLD: Around 350 species around the world, 25 species in North America, and 16 species in the western U.S. and Canada. CLEPTOPARASITES: In North America, none known. IDENTIFYING FEATURES: Mostly hairless gunmetal green/black bees of small size. HEAD: Usually yellow markings on the lower portion of the clypeus; in males more

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Cly

c

Ceratina  239

prominent, and often with a line running up the center of clypeus, like an upsidedown T. THORAX: Elongated. WINGS: Three submarginal cells. ABDOMEN: Same width as the thorax. The apex of the abdomen often comes to an abrupt point. Each tergal segment constricts at its apex, giving the abdomen edges a wavy appearance. SIMILAR GENERA: The small size and dark coloration can make Ceratina appear similar to Hylaeus and Lasioglossum (especially L. [Dialictus]). Hylaeus have two submarginal cells, and the overall body shape is skinnier. In males, the markings on the face are distinctive. In Hylaeus the males have yellow next to each compound eye; in Ceratina the yellow is restricted to the clypeus, usually in the center. Hylaeus abdomens do not constrict to a sudden point, and they are not as shiny as Ceratina. Lasioglossum (Dialictus) do not have yellow on their faces. They tend to be greener, and often have noticeable hair bands on the abdomen. The basal vein on Ceratina can appear arcuate, as in L. (Dialictus), which can be confusing. The hair bands and abdominal shape should be sufficient characters to distinguish the two.

— Ceratina arizonensis SIZE: Petite; 3–5 mm. PHENOLOGY: April through July. FLORAL HOSTS: Generalist. RANGE: Central California to Idaho, east to Texas. Also found in Hawaii. NESTING: Twig nester. IDENTIFICATION: Small shiny black bee. HEAD: Black, round, shiny head, eyes converging slightly below. Very few pits. In females, the clypeus has a long ivory mark at the center. In males, the clypeus is entirely ivory, as are the areas beside the clypeus. THORAX: Scutum with very few fine pits, close together at the sides and posteriorly. Metanotum finely and closely pitted. Pronotum finely punctured at its sides. LEGS: In females, scopa is loose, widely spaced, and somewhat branched on outer surface of tibiae. ABDOMEN: First Clypeus and areas next to the clypeus yellow

Ceratina arizonensis (male)

Long ivory mark on the clypeus

Shiny black head and thorax Ceratina arizonensis (female)

Abdomen brownish black

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tergal segment sparsely pitted at the apex. Second and third tergal segments with no pits. In males, T7 has wide angles on either side, when viewed from above. SIMILAR SPECIES: There are only two small black shiny species of Ceratina. Females of the two are indistinguishable except by distribution. C. cockerelli is found in eastern Texas and other eastern states. Ceratina arizonensis is found in northern and western Texas to California. Males of the two can be distinguished by the marks on the face, which are reduced to small oval marks to either side of the clypeus in C. cockerelli.

— Ceratina acantha SIZE: Small; 6–9 mm. PHENOLOGY: May through November. FLORAL HOSTS: Generalist. RANGE: British Columbia south to California, east to Idaho and Utah and south to New Mexico; absent from the Great Basin. NESTING: Twig nester, including Sambucus and Ailanthus. IDENTIFICATION: Dark metallic green to blue-green bee. HEAD: Blue green and shiny, with pits. The clypeus is impunctate, with ivory marks on the clypeus. THORAX: Pits on side of thorax widely spaced, more than a pit’s width apart. Little to no ivory on pronotal lobes. Scutum and scutellum with few pits. On the sides of the thorax, there are fine, sparse pits. LEGS: In males, there is a large sharp tooth on hind femur. ABDOMEN: First tergal segment with fine, widely spaced pits. On T2–T5 the area just above Ceratina acantha (male) the apex is impunctate, shiny. SIMILAR SPECIES: See C. nanula.

Lower portion of clypeus ivory Sharp tooth on hind femur

No ivory mark on clypeus

Dark pronotal lobes

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Ceratina acantha (female)

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— Ceratina nanula SIZE: Small; 5–8 mm. PHENOLOGY: April through August. FLORAL HOSTS: Generalist. RANGE: Colorado and Texas west to California and British Columbia. NESTING: Twig nester. IDENTIFICATION: Small, metallic blue Ceratina. HEAD: Large head, shiny between pits. In females, there is a large almond-shaped ivory mark in the center. In males, the clypeus is yellow, and shaped like a top hat. THORAX: Scutum shiny, with few pits. Metanotum with fine shallow pits all over, moderately spaced. Pronotal lobes ivory. LEGS: In females there are yellow marks on the leg joints. In males, the hind femur has a pointed tooth. ABDOMEN: In females, the sixth tergal segment has a distinctive notch when viewed in profile. In males, the pygidial plate of T7 is inconspicuous. SIMILAR SPECIES: Similar to C. acantha, but that species is darker in color, has dark pronotal lobes, and little punctation on the sides of the thorax. In males, the femoral tooth is larger in C. acantha. Ceratina apacheorum also appears similar to C. nanula, but is smaller. In male C. apacheorum there is a sharp preoccipital carina, absent form C. nanula; and the hind femur has a pointed tooth that is rounded in C. nanula. Ceratina hurdi is especially difficult to separate; in males, there is a broad plate on T7, not seen in C. nanula. In females, the pits on the sides of the thorax are

Ivory pronotal lobes

Ceratina nanula (female)

Ivory mark in the center of the clypeus

r Ceratina nanula (male)

Pointed tooth on hind femur

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Clypeus is yellow, making a shape like a sombrero

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smaller and more widely spaced in C. hurdi than in C. nanula, and there is less ivory coloring on the face of C. nanula. Ceratina shinnersi females are indistinguishable from C. nanula, but C. shinnersi is only in Texas.

— Ceratina pacifica SIZE: Small; 6–9 mm. PHENOLOGY: April through August. FLORAL HOSTS: Generalist. RANGE: Widespread throughout the western U.S. and British Columbia, extending as far east as Colorado and New Mexico. NESTING: Twig nester. IDENTIFICATION: Dark, metallic blue-black bee. HEAD: Dark metallic, with few pits. In females, very small yellow dot on clypeus. In males, ivory mark shaped like a hat covers clypeus and small area above clypeus. THORAX: Scutum shiny, with few pits except along parapsidal lines. Metanotum with more punctation, fine, and closely spaced. The sides of the thorax are covered with coarse pits that are less than a pit’s width apart. LEGS: In males, there is a shiny protrusion on the midfemur. ABDOMEN: First tergal segment with fine sparse pits on the dorsal surface. On T2–T5 there are random, finely scattered pits, just above the apical margin. In females, there is a hair tuft on the protrusion that appears at the middle of T6. SIMILAR SPECIES: Similar to C. neomexicana, but that Yellow spot species, in females, does not on clypeus have the hair tuft on T6. In Ceratina pacifica (female) males, C. pacifica has a shiny protrusion on the midfemur; this is dull and not as well defined in males of C. neomexicana. Ceratina pacifica In certain parts of its range, (male) Yellow clypeus C. pacifica overlaps with C. punctigena, which also has a hair tuft on T6 in females, but the latter has a spine on the gena, which C. pacifica does not. In males, the protrusion on the midleg of C. pacifica is flattened in C. punctigena.

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DIADASIA — SUBFAMILY: Apinae — TRIBE: Emphorini OVERVIEW: Hairy, fast-flying bees seen most often in early to midsummer. All species are specialists; in North America, these bees specialize on just one of five plant families (Asteraceae, Onagraceae, Convolvulaceae, Cactaceae, and, most commonly, Malvaceae). Bees nest in the ground, with many species creating elaborate turrets, periscopes, or chimneys over their nest openings, which are usually in hard-packed dry earth. IN THE WORLD: North, Central, and South America; amphitropically distributed so the genus occurs on either side of the tropics, but seldom within the tropics. About 45 species altogether, with 30 in the U.S. and Canada. Twenty-five species occur in the West; they are often very abundant. CLEPTOPARASITES: None known. IDENTIFYING FEATURES: Bees of variable size, from 5 to 20 mm; fuzzy, but with a shiny black integument below. HEAD: Narrower than width of thorax when viewed from above. Eyes often with bluish tinge. Face appears consistently oval, rounded on top, and not flattened as in some other Apidae. The tongue is relatively short, when extended, not reaching even to the middle of the thorax. The first flagellar segment of the antennae is short—less than twice as long as width. THORAX: In males, the propodeal region is bare of hair, and usually heavily polished. LEGS: There is an arolium between the front claws. In many females, the front legs have long dense hairs on the base of the front femur, and the scopal hairs on the hind legs all curve up and in at their tips. In males, the claws of the hind legs are usually broad and rounded. ABDOMEN: Many species have distinct apical hair bands running across the terga. Though difficult to see, on S2 there is a raised lateral line that is produced at its middle. There is no easily accessible published key to North American Diadasia, so identifying Diadasia to species can be difficult. Using the plant family on which the bee is found can help narrow down the possibilities, and knowing the range of the bee can also help. SIMILAR GENERA: May look similar to other large fuzzy Apidae. Can be distinguished from most by smaller head width, and the rounded vertex (Eucerini, for example, are flattened across the top of the head). The wing venation is also unique—Anthophorini and Eucerini species lack the longer cubital cell, and the distance between the two portions of the lower vein of the radial cell is more or less equal in other bee groups. Scopal hairs, though dense in all very fuzzy Apidae, distinctly curl in and up in Diadasia. Finally, the raised ridge on the second sternal segment is unique, among Apidae, to Diadasia, though it is difficult to see.

— Diadasia australis SIZE: Medium to large; 13–16 mm. PHENOLOGY: May through August. FLORAL HOSTS: Specialist on Cactaceae, including prickly pear, cholla, and other cacti. RANGE: Mexico north to southern Canada. Largely absent from the Pacific Northwest. As far east as Kansas, South Dakota, and eastern Texas. NESTING: Ground nester, often in dense

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aggregations of 100 to 1,000 individuals in hard-packed soils, including dirt roads and well-used trails. Newer nests may have a small “turret” or “chimney” of sculpted earth marking the entrance. IDENTIFICATION: Large, light-colored fuzzy bee seen rummaging in cactus flowers when they bloom. HEAD: Mandibles black throughout, maybe fading to a reddish color at the tips. The vertex is roughened between the pits. In females, the first flagellar segment is long, about one and a half times as long as it is wide. In males, the inner margins of the compound eyes are parallel, not converging toward the mandibles. THORAX: Shining, with wide deep pits. The propodeal enclosure (the small triangle on the propodeum that faces the abdomen) is moderately dull, the Hind tibial spurs hooked at the apex edges running straight from top to bottom, and it is completely bare. LEGS: The hind tibial spurs are strongly hooked at their apices. In females, front femur is smooth, with no long projections. Also in females, the scopal hairs are red/orange on the inner surface, contrasting with the

Diadasia australis (female)

Specialist on cactus flowers

Diadasia australis (male)

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pale hairs on the outer surface. In males, the hind basitarsus has a projection on the inner side that is comma-shaped. ABDOMEN: The hair on the abdomen is short and entirely pale to light gold; there are no dark brown hairs at the base of any segment. Distinct apical bands run across each tergal segment. In females, the hairs on T5 are darker at their ends than on the basal half. SIMILAR SPECIES: Diadasia australis is very similar to other cactus-specializing bees in the West, most notably D. opuntiae and D. rinconis. There is also one larger western species, D. megamorpha, that looks similar because of its larger size. It is a specialist on Sphaeralcea, however, and seldom seen. Diadasia rinconis tends to have a larger, shinier propodeal enclosure in females. The vertex tends to be smooth between pits, rather than roughened, as it is in D. australis. And it is slightly smaller in size. With D. opuntiae, the propodeal enclosure is covered in hair, while it is bare in D. australis. Diadasia australis may also appear similar to D. enavata. See D. enavata for ways to distinguish.

— Diadasia enavata SIZE: Medium to large; 14–16 mm. PHENOLOGY: May through September, when sunflowers (Helianthus) are in bloom. FLORAL HOSTS: Strict specialist on sunflowers (Helianthus); may be seen on occasion foraging for nectar on other plants, especially other Asteraceae. RANGE: Widely distributed. Found across the Midwest, west to the California coast, far south into Mexico. NESTING: Ground nesting. IDENTIFICATION: Large, pale, fuzzy bee seen frequently on sunflowers. HEAD: Hair on the head is entirely pale. The mandibles are dark at their bases. In males, the inner margins of the compound eyes converge strongly toward the mandibles. THORAX: The propodeal enclosure is dull, not shiny at all. The scutum has light-colored hairs surrounding a large mostly bare patch at the center. Diadasia enavata LEGS: In females, the hind tibial (female) spurs are straight, or just slightly curved at the very tip. On the front legs of females, The clypeus the hairs of the doesn’t protrude basitarsus are very very far from On the female there are long the face. long, with feathery curved hairs on the femur. The scopal hairs are thick, branches when viewed feathered, and each one There is an arolium between curves in just a little. the claws in Diadasia. under a microscope or with

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246  Apidae The vertex of the head

a hand lens. In males, the hind is curved, rather than flat as in similar looking basitarsus has a projection bees (like Anthophora). at the apex that is enlarged, shaped like a comma, and Diadasia extending nearly to the enavata (female) beginning of the next tarsal segment. ABDOMEN: Hair on the tergal segments is entirely pale and erect, standing straight up to almost straight The thorax is covered in pale gold hair, more or less dense up on each tergal segment. depending on the age of the specimen. On T3 and T4, the hair is pale, with no appressed dark hairs anywhere. Scopal hairs are The sixth sternal segment has a short numerous, thin, brush of pale hair at its base, with and wispy. no tufts on the sides. SIMILAR SPECIES:

The head is much narrower than the width of the thorax.

Diadasia enavata (male)

Diadasia enavata females appear similar to D. rinconis and D. australis, both specialists on Cactaceae. They can be distinguished by the hind tibial spur, which is strongly curved in both male and female D. rinconis and D. australis, and in females by the hairs on T5, which are darker at their bases than at the ends in D. rinconis and D. australis but are darker at their ends than at the base in D. enavata females. With males, few species have the enlarged projection on the hind basitarsus. Diadasia vallicola does, but the hair on the abdomen is much darker in this bee.

— Diadasia bituberculata SIZE: Medium; 10–13 mm. PHENOLOGY: May through early August. FLORAL HOSTS: Specialist on Convolvulaceae, especially Calystegia (bindweed) and Convolvulus (morning glory). RANGE: Restricted almost entirely to the Pacific Coast; California and southern Oregon, with a few records across the Sierra Nevada into Nevada at higher elevations. NESTING: Nests in gregarious groups of 100 or more individuals. Nests have small turrets over the entrance, which are thought to help prevent infilling with dirt and nearby debris. IDENTIFICATION: Dark bee often seen burrowed in at the bases of morning glory or bindweed flowers. HEAD: Hair on the head is entirely pale. The mandibles are dark at their bases. In males, the inner margins of the compound eyes are nearly parallel.

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Diadasia  247 THORAX: Shining, with distinct deep pits throughout. In females, hair on thorax is a light red/brown on the top, fading to white on the sides and below. In males, the surface is clearly visible through the rather sparse white hairs. The propodeal enclosure is dull, as if rubbed with a piece of sandpaper. LEGS: Hind tibial spurs are straight at the apex. In females, the scopal hairs are dense and black. In males, the legs are covered with long erect white hairs, and the hind basitarsus is flattened, only slightly widened at its apex. ABDOMEN: Abdomen has white hairs that stand up, thicker on T1 and T2, though the integument is clearly visible beneath. On T3–T6 there are more black hairs than white on the main surface, but there are Black scopa also dense white appressed apical hair bands present on T2–T5. On T6, the apex has two teeth that are broad, and not very pointy, widely separated from each other.

Diadasia bituberculata (female)

SIMILAR SPECIES:

The black scopal hairs separate females of this species from all others that are similarly sized. As the only specialist Diadasia on Convolvulaceae, this can also help to distinguish. With males, it is most similar to D. angusticeps. The polished propodeal enclosure can distinguish the two, since it is rough in D. bituberculata. Also, D. angusticeps is smaller, and specializes on Onagraceae, especially Clarkia.

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Diadasia bituberculata (male)

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— Diadasia diminuta SIZE: Small; 6–9 mm. PHENOLOGY: Very long flight season, early April through early October. FLORAL HOSTS: Specialist on Malvaceae, especially globe mallow (Sphaeralcea). RANGE: Broad distribution, ranging from the Mexican border (in fact, clear to Panama) north to Alberta, Canada. East to South Dakota, Oklahoma, southern Manitoba, and eastern Texas. Especially common in the southwestern U.S. NESTING: Ground-nesting bee, often in dense aggregations on hardpacked trails and bare soil. May nest with other Diadasia species. Nests have tunnels built over the top of the actual entrance, along the earth’s surface. IDENTIFICATION: Small gray bee commonly seen encircling the ball of anthers in a globe mallow flower. HEAD: Small head, slightly longer than wide. Mandibles are dark at bases. THORAX: The thorax is covered in relatively long dense hairs over the whole surface. The propodeal enclosure is shiny and relatively large. LEGS: On the hind leg, the tibial spur is straight at its apex. In females, scopal hairs are light colored. ABDOMEN: In females, Diadasia diminuta T2–T4 have entirely pale to golden (female) hair, with no dark brown or black hair occurring near either the apex or the base (so no appearance of light and dark bands on the abdomen). The hair is thick enough to almost conceal the surface of the tergal segment completely; it is even more dense near the apical margins, so that very light white bands run across each, with lighter, longer hairs over the top. Hair on T5 is the same color as that on the rest of the tergal segments. In males, the hair on the abdomen stands up, giving a loose, fluffy appearance. Also in males, S6 has dense brushes of hair on either side of center.

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Ancyloscelis  249

SIMILAR SPECIES: This small bee appears most similar to D. sphaeralcearum, Diadasia diminuta D. lutzi, and D. vallicola, all of which (male) also specialize on Malvaceae. In D. sphaeralcearum, the hair on the abdomen in males is appressed, as opposed to the mostly erect hairs of D. diminuta. In females, D. diminuta is slightly larger than D. sphaeralcearum, with fewer hairs on the abdomen, and a polished propodeal enclosure, which is dull and roughened in D. sphaeralcearum. In males of D. lutzi, there are black hairs mixed in with the pale hairs on the tergal segments. In females, the hair on the abdomen of D. lutzi is thin, so that the surface can be easily seen through. In D. diminuta, the hair is denser, obscuring most of the surface. With D. vallicola, the hair on the surface of the tergal segments is more appressed, and the underlying apical hair bands are broader, and less well defined.

ANCYLOSCELIS — SUBFAMILY: Apinae — TRIBE: Emphorini OVERVIEW: Small dark bees with long back legs and a shiny thorax. Specialists on plants in the Convolvulaceae, and most commonly found in Ipomoea. Nest in the ground, sometimes in aggregations, and with other ground-nesting genera and species. Some species of Ancyloscelis have been found nesting in adobe bricks. IN THE WORLD: 20 species in the world; three occur in North America. CLEPTOPARASITES: Unknown. IDENTIFYING FEATURES: Small bees, males with long curved legs. HEAD: Wider than long, but not as wide as the thorax. There is a carina running along the inner margins of the compound eyes. The clypeus is strongly protuberant. The male mandible is short and curves gently. In males, clypeus and mandibles often have pale markings. THORAX: Dark, often shiny, with some sparse hair, especially near the anterior part. WINGS: On the hind wing, the cell on the second row is short, not half the length of the cells on the upper row. LEGS: In females, scopal hairs are stiff, feathery, and widely spaced. In some species, the scopae are different colors on the hind tibia and basitarsus. In males, the hind femurs are inflated, elongated, and curved. The tibiae are hooked. ABDOMEN: White stripes run across each tergal segment. In males, T1 is rounded and curves apically.

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SIMILAR GENERA: Appears similar to Exomalopsis, which is also small. The clypeus is much less protuberant in Exomalopsis than in Ancyloscelis. And the hind leg in male Exomalopsis is not expanded.

— Ancyloscelis sejunctus SIZE: Small; 6–8 mm. PHENOLOGY: August and September. FLORAL HOSTS: Specialist on Ipomoea. RANGE: Colorado, Texas, New Mexico, and Arizona. NESTING: Ground nester. IDENTIFICATION: Small black bee with white hair bands; males with very long hind legs. HEAD: Females with light-colored mandibles, slightly darker at the tips. Head pitted evenly across its entire surface. In males, the clypeus is black, and the labrum is mostly black. THORAX: Dark, with wide evenly spaced pits. LEGS: In males, the hind tibia is hooked below the lower half. Also in males, there is a large tooth at the base of the posterior basitarsus. ABDOMEN: Broad stark white stripes run across each segment, slightly interrupted at the center of T1 and T2. SIMILAR SPECIES: There are only three species of Ancyloscelis north of the U.S.-Mexico border. Ancyloscelis melanostoma has dark brown mandibles from base to tip. Ancyloscelis

Ancyloscelis sejunctus (female)

Ancyloscelis sejunctus (male)

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sejunctus has pale mandibles, especially at the base. Ancyloscelis sejunctus and A. apiformis females are nearly indistinguishable. The latter is known in the U.S. only from Texas, while A. sejunctus occurs as far north as Colorado, and from Texas to Arizona. Ancyloscelis apiformis has a slight impunctate raised line running down the middle of the head.

EUCERA — SUBFAMILY: Apinae — TRIBE: Eucerini OVERVIEW: Larger bees, often noticed because of the protruding clypeus, or the long antennae in males. Some species are distinctly spring, but with multiple unique subgenera, there are also summer and fall species. The genus includes specialists (with many on Asteraceae) and generalists. All nest in the ground, usually in modest holes with little externally visible modification. IN THE WORLD: Found around the world, with 220 species distributed mostly in the Northern Hemisphere; Japan through Central Asia, west to Spain and the Canary Islands. In the U.S. there are six subgenera, many of which used to be genera (number of U.S. species listed in parentheses): Synhalonia (55 species), Cemolobus (1 species), Peponapis (6 species), Xenoglossodes (22 species), Xenoglossa (4 species), and Syntrichalonia (1 species). We highlight 8 of the more than 70 western species. CLEPTOPARASITES: Triepeolus. IDENTIFYING FEATURES: Large, fuzzy bees. HEAD: The clypeus sticks out notably from the face and is often yellow. The proboscis is very long. In males, the antennae are long and completely black. WINGS: In North American species, there are three submarginal cells. Small erect hairs occur inside the cells on the wing. LEGS: Arolia present. ABDOMEN: There are often abdominal stripes. When present, they are at the base of each tergal segment, and often wrap around to the sternal segments underneath. SIMILAR GENERA: Melissodes are similar in appearance. Differences between Melissodes and Eucera can be hard to see. Melissodes have tegulae that are pointed at the anterior end, but rounded at the posterior end, giving them a tear-drop shape. Eucera have round tegulae. This is a difficult character to see in fuzzy specimens, and hair may need to be scraped aside. In general, Melissodes fly later in the year and are smaller than most western Eucera. Anthophorini, like Anthophora and Habropoda, appear similar and many fly at the same time; their wings are not hairy inside the cell margins, as Eucera wings are. Recently, species of Eucera (Synhalonia), Peponapis, Xenoglossa, Cemolobus, and a host of others in various eucerine bee genera were found to be similar enough to each other, and different enough from everything else, to warrant putting them all in the same genus, and making the old genus names into subgenera. Thus, the squash bee Peponapis is now Eucera (Peponapis). If you are looking for additional information on these species, you might need to search for them under their older names as well. The characters describing the bee have not changed, only its name, to reflect

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its relationships more accurately with other bees. However, coming up with general characters that unite the bees in the same genus has become more complicated. Be patient with yourself as you learn to distinguish between these subgenera. Below are a few key points for the subgenera covered in this book. Eucera (Synhalonia): Three submarginal cells. Includes all Eucera sensu strictu in North America. Next to each compound eye there is no strong carina, especially toward the lower half of the face (as is seen in other Eucerini). Also, the hair bands on tergal segments of the abdomen often run underneath, and across each sternal segment. Eucera (Xenoglossodes): Small group that includes what used to be Tetraloniella. Medium-sized, long antennae. Pale abdominal hair bands, especially in males. Eucera (Peponapis): Extremely protuberant clypeus. Bees are usually seen in or near squash flowers. Eucera (Xenoglossa): On the antennae in males, the first flagellar segment is significantly longer than the second. In most Eucera, the first flagellar segment is very short. In females and males, there is a tooth on the inner margin of the mandible, right near the base.

— Eucera (Synhalonia) edwardsii SIZE: Medium;

10–14 mm. through June. FLORAL HOSTS: Generalist. RANGE: Western North America, more common at higher elevation, and largely absent from hot deserts. NESTING: Ground nester. IDENTIFICATION: Gray fuzzy bee seen in the spring. HEAD: Broader than long, with parallel eye margins. In females, dark clypeus is finely and densely pitted; hidden beneath pale long hair. In males, the clypeus is all yellow and slightly polished, but at the sides, there is a strong notch in the yellow, giving it a squared-off appearance; the yellow of the clypeus almost touches the inner margin of the compound eye. The labrum is also yellow. Also in males, antennae are long. THORAX: Buff colored, with thick hair covering the scutum and posterior thoracic parts. Hair underneath tegula on sides of the thorax is all light colored. Tegulae are brown. WINGS: Slightly smoky. LEGS: In females, the scopal hairs are pale, as are the hairs on the inner surface of the hind basitarsus. ABDOMEN: In females, hair on T1 is the same color and length as that on the thorax. The second through fourth tergal segments each have bands of white hair that extend broadly across the segment, just before the apex. On T3 and T4 the basal half of each tergal segment has black hair. In males, T3–T7 have all-black hair. The first and fifth tergal segments are covered in light-colored hair. On T2 of males, there is white at the base. PHENOLOGY: May

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Eucera edwardsii (female)

SIMILAR SPECIES: Most similar to other western Eucera (Synhalonia), including E. angustior, E. frater, and E. Eucera edwardsii cordleyi. In fact, for females, (male) distinguishing these species may be difficult to do without reference material. Eucera cordleyi has a narrower white band on T2, especially toward the sides, where black hairs are intermixed, than does E. edwardsii; however, there is gradation, so that some E. edwardsii females share the characteristics of E. cordleyi. In E. frater, the hair bands on the abdomen of females are incomplete. In males, the hair patterns on the abdomen (all black except for T1) and the square notch on the clypeus are distinctive.

— Eucera (Synhalonia) frater SIZE: Medium; 12–13 mm. PHENOLOGY: April through August (may have more than one generation per year). FLORAL HOSTS: Specializes on Fabaceae, mostly milkvetch (Astragalus). RANGE: Widespread western species (especially common in the Northwest and in California), rare in the Great Basin and the lower elevations of North America’s hot deserts. NESTING: Ground nester. IDENTIFICATION: Large fast-flying bee often seen on milkvetch in the spring. HEAD: Wider than long, eyes very nearly parallel. In females, hair on the face is light colored. In males, clypeus and labrum are yellow. The side of the clypeus is moderately angled, but not to a 90° angle, and the yellow ends well before the inner margin of the compound eye.

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254  Apidae THORAX: In both males and females, covered in long blonde hair, including under the tegula on the side of the thorax. Tegulae are dark brown. WINGS: More or less clear. LEGS: Scopal hairs typically black with some orange hairs on tibiae, but may have all scopal hairs orange (see subspecies below). ABDOMEN: In females, the first tergal segment is all pale hair. In some subspecies a white hair band runs completely across T3 and Eucera frater (female) T4 but is incomplete on T2 (see below for other variations). SIMILAR SPECIES: There are three subspecies of E. frater; males are very difficult to tell apart. Eucera frater albopilosa occurs only in California. This species has dark scopal hairs in females, and the hair on the abdomen is all black, beyond T1. This subspecies appears similar to E. atriventris. In E. frater albopilosa, the clypeus is smaller, and less bulging than that of E. atriventris, and the recurrent vein meets the second submarginal cell near its center in E. atriventris, as opposed to near the end in E. f. albopilosa. Eucera frater frater is found in Colorado, west to Nevada, and north to Idaho and Wyoming. Eucera frater In this subspecies, the (male) scopal hairs are all red and orange. Eucera frater lata is found in the northwestern states and into British Columbia. It has dark scopal hairs, but white hair bands on T3 and T4 as would be seen in E. f. frater.

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Eucera frater (female)

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— Eucera (Synhalonia) fulvitarsis SIZE: Medium; 10–13 mm. PHENOLOGY: May through June; a few later dates suggest this species may have more than one generation per year. FLORAL HOSTS: Appears to be a generalist. RANGE: Western states, east of the Sierra Nevada. Most common in the Great Basin and Colorado Plateau. May occasion the western edge of the Great Plains. NESTING: Ground nester. IDENTIFICATION: Large dark bee, often with striking orange scopal hairs seen in the spring in the Great Basin. HEAD: Wider than long, eyes very nearly parallel, vertex, with ocelli, not raised as far above line running between compound top of compound eyes as in some species. In females, hair on the face is black, barely covering black shining clypeus. Also in females, there is thick short hair on the proboscis (the longer portion of the tongue). In males, clypeus is Eucera fulvitarsis yellow, not strongly notched on (female) the sides. THORAX: On the dorsal parts of the thorax, hair is a mix of pale and dark shorter hairs. Hair on the area under the tegula (the side of the thorax) is all dark. Tegulae dark brown. WINGS: Clear, with slight brown tinge. LEGS: In females, scopal hairs bright orange to red; all other hairs on legs dark. In males, the mid basitarsus, which is reddish, is narrowed at its apex, and then Eucera fulvitarsis drawn out into a comma(female) shaped spur. ABDOMEN: In females T1 is light, as is the base of T2. The second tergal segment is smooth and lacks pits across much of the base. The third and fourth tergal segments are dark, with no white bands in most individuals. In males, T1 and T2 are sparsely covered in light hair. The third through fifth tergal segments are thinly covered with dark hair.

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SIMILAR SPECIES:

The reddish scopal hairs and unique hair patterns on the abdomen are relatively distinctive in females. Moreover, the hairy proboscis is an uncommon trait. In this characteristic it appears most similar Eucera fulvitarsis to E. acerba, but that (male) species has curved hairs on the proboscis, and the scopal hairs are black, while the abdomen has pale stripes, and shallow pits at the base of T2. Males can be difficult to distinguish from other Eucera. The long comma-shaped spur on the midtibia should rule out many otherwise similar species.

— Eucera (Peponapis) pruinosa SIZE: Medium;

12–14 mm. and August. FLORAL HOSTS: Specializes on Cucurbita (squash and pumpkins). Common inhabitant of gardens with squash and pumpkin. Males can be found in these flowers in the morning or late evening, even once the flower is wilted. Females usually forage in the early morning as well. RANGE: Widespread across the U.S.; rare in the Pacific Northwest. NESTING: Ground nester; often seen in the vicinity of the squash plants it visits. PHENOLOGY: June

IDENTIFICATION:

Eucera pruinosa (female)

Larger fast-flying bee, seen in the early morning on pumpkin and squash flowers. HEAD: Clypeus sticks out from face and is Scopal hairs about as tall as the width widely spaced of the compound eye. In males, there is a yellow circular or triangular spot right in the center of the clypeus. The antennae in males

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Clypeus sticks out from face.

White hair bands complete (or nearly so); their flattened nature gives the abdomen the look of being lightly frosted.

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are somewhat long, extending just past the wing bases. THORAX: Uniformly hairy with umber-colored hair. LEGS: In females, scopal hairs are light brown, and There is a small yellow widely spaced. spot right in the center of the clypeus in males. ABDOMEN: Strong frosty hair bands, slightly appressed, run across the abdomen in both males and females. SIMILAR SPECIES: Eucera (Xenoglossa) strenua is also commonly found in Eucera pruinosa (male) squash flowers, but some differences are apparent. See E. strenua for specifics.

This bee is most commonly seen flying in the early morning, or sleeping in squash flowers in the evening.

Hair bands are visible on the bee’s abdomen as it rummages deep in squash flowers. Flattened white stripes run across the center of T2–T5.

— Eucera (Xenoglossa) strenua SIZE: Medium to large; 14–18 mm. PHENOLOGY: June and September. FLORAL HOSTS: Specializes on Cucurbita. Common inhabitant of gardens with squash and pumpkin, and most often seen in the morning, when squash blossoms are open. Males can be found in these flowers in the morning or late evening in wilted flowers. RANGE: Widespread across the U.S.; absent from northern states, including North and South Dakota, Montana, Idaho, Wyoming, and Minnesota. NESTING: Ground nester; often seen in the vicinity of the squash plants it visits. IDENTIFICATION: Orange fuzzy bee with frosty white stripes on the abdomen. Most commonly found in squash blossoms, but larger than Eucera (Peponapis). HEAD: Clypeus Clypeus sticks out from face.

Though E. (Xenoglossa) shares more than a passing resemblance to E. (Peponapis), the integument of the abdomen is more polished in the former than the latter.

Eucera strenua (female)

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Look at the beautiful, perfectly circular pollen grains from squash on the body of this bee.

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Eucera strenua (male)

Males have bands of short white flattened hair on the abdomen, slightly interrupted in the middle of T2.

Clypeus protrudes significantly from face.

sticks out from face and is about as tall as the width of the compound eye. Labrum and mandibles in female are yellow while clypeus is mostly black, but it may have yellow at its rim. In males, labrum, mandibles, and clypeus are yellow. The inner margins of the compound eyes diverge slightly but are relatively close to parallel. The lateral ocelli are not overly close to the inner margin of the compound eyes. The antennae in males are long. In both sexes the first flagellar segment is about as long as the second and third segments combined. THORAX: Thickly covered in auburn hair. LEGS: Scopal hairs are long, and exceptionally widely spaced. In males, legs are orange. ABDOMEN: In females, T1 is covered in erect hairs, at least basally. Appressed hair bands run across T2–T4 but are interrupted in the center, especially on T2. SIMILAR SPECIES: Looks very similar to Eucera (Peponapis) pruinosa, but is slightly bigger, and with yellow mandibles. Eucera (Xenoglossa) kansensis overlaps with E. strenua, especially in the Midwest. In E. kansensis, the clypeus of females is yellow to white, with the coloration covering about half the total surface of the clypeus. In males of E. kansensis, the legs are a red/brown color.

— Eucera (Xenoglossa) angustior SIZE: Small

to medium; 8–11 mm. through August, when gourds bloom. FLORAL HOSTS: Cucurbitaceae, including squash, pumpkins, and native gourds. RANGE: Extreme southwestern U.S., north to central California, and east to western New Mexico. NESTING: Ground nester. IDENTIFICATION: Brilliant orange bee seen rummaging in squash flowers in the summer. HEAD: Clypeus lemon yellow, as are mandible bases. The clypeus (in profile) is not overly PHENOLOGY: July

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Very little hair on T2

Eucera angustior (male)

protuberant, sticking out less Legs are entirely than the width of the compound Eucera angustior red. (female) eye. Lateral ocelli are relatively close to the compound eyes, less than their own width away, and they are enlarged and rounded. In males, the first flagellar segment is elongated, twice as long as the second flagellar segment. Also in males, the clypeus is close to the eyes, which diverge strongly below. THORAX: Covered in thick straw-colored hair. Tegulae are auburn. LEGS: In females, legs are entirely red. Scopal hairs are light colored. ABDOMEN: The first tergal segment has sparse hair the same color as the thorax. In females, Eucera angustior (male) T2 is mostly without hair. In males, pygidial plate is long but tapers evenly, with no clear point. SIMILAR SPECIES: Eucera angustior is distinctive among Eucera (Xenoglossa) because of the widely diverging eyes, and large ocelli (especially in females). It appears most similar to E. patricia and can be told apart mostly by the lateral ocelli, which are closer to the inner margins of the compound eyes in E. angustior but separated by more than an ocellus’s width in E. patricia. In males, the pygidial plate also differs, being constricted at the middle in E. patricia, rather than consistently narrowing. Also, there is little overlap in the range of these two species: E. angustior is found west of the continental divide, in Arizona and California, while E. patricia is found east of the continental divide, in New Mexico and Texas.

— Eucera (Xenoglossodes) eriocarpi SIZE: Small; 7–9 mm. PHENOLOGY: July through October. FLORAL HOSTS: Specialist on Asteraceae. RANGE: California east to Texas; north to Utah and Colorado. NESTING: Ground nester.

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IDENTIFICATION: Small, prim, gray bee, seen in the summer months on globe mallow (Sphaeralcea). HEAD: In both sexes, the mandibles are yellow at their bases, and the labrum is entirely yellow. In females, clypeus has a yellow band running across the apex, and often, yellow spots, with a small yellow area just above its top edge. In males, the clypeus is completely yellow. Also in males, antennae are long and completely yellow to orange underneath. The first flagellar segment is very short, only an eighth, at most, the length of the second segment. THORAX: The scutum has widely spaced pits on a shiny surface. The tegulae are strongly convex on the anterior portion, not straight or curved in. LEGS: Scopal hairs thick, very branched, and pale. ABDOMEN: In females, T1 is densely pitted just before it turns up from facing the thorax. Tergal segments 3–6 are covered with white to yellow hair, and bands are not clearly evident. On T2 there is a complete apical hair band, separated from the hair at the base of the segment by a few simple pale hairs. Also in females, pygidial plate is V-shaped. In males, S6 (which is hard to see) has teeth at its lateral margins. SIMILAR SPECIES: Eucera Eucera eriocarpi (female) (Xenoglossodes) eriocarpi is very similar to E. wilmattae. The two can be separated in males by the carina on S6, which forms a concavity in E. eriocarpi, but is straight in E. wilmattae. The two may be impossible to distinguish in the field. Females of the two are easier; in E. eriocarpi, there is yellow on the labrum, while in E. wilmattae it is mostly black, or at least rimmed with black. Eucera eriocarpi (male)

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— Eucera (Xenoglossodes) lippiae SIZE: Small

to medium; 9–12 mm. through September. FLORAL HOSTS: Specialist on globe mallow (Sphaeralcea sp.). RANGE: Arizona, New Mexico, and Texas. NESTING: Ground nester. IDENTIFICATION: Small bee with closely cropped hair and with white abdominal bands. HEAD: In females, the clypeus has a yellow mark on its apical half, with a small yellow triangle extending up toward the antennae at the center. In males, the clypeus is entirely yellow. In both sexes, the mandibles are yellow at their bases, and red at the tips, and the labrum is entirely yellow. In males, the flagella are long and black, flattened, and there is a wavy margin along the last five segments. THORAX: Scutum has deep, small punctures on a shiny surface, about one pit’s width (or less) apart. Tegulae yellow, convex at their anterior outer margin. LEGS: In females, scopal hairs are pale, and heavily branched. ABDOMEN: In females, T2 and T3 have bright white hair bands, just above the apical margin, that run thickly across the width of the segment, and also basal white hair bands. The apical hair band on T2 is interrupted at the center (this is true in both males and females). SIMILAR SPECIES: Eucera lippiae is similar to E. spissa. The latter has apical pale hair bands in females (instead of subapical). Eucera lippiae PHENOLOGY: August

(female)

Eucera lippiae (male)

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MARTINAPIS — SUBFAMILY: Apinae — TRIBE: Eucerini OVERVIEW: Striking fluffy bee with golden to red hairs on the thorax, and black-andwhite stripes on the abdomen. Seen mostly at dawn and dusk, in deserts and arid regions of the southwestern U.S. Presumed to nest in the ground. IN THE WORLD: Three species occur in the world, two in North America and one in the Andes. They are restricted to the desert Southwest. CLEPTOPARASITES: Possibly Triepeolus. IDENTIFICATION: HEAD: Clypeus sticks out from plane of face. Mandible is simple in males, and with two teeth in females. In males, face narrow, antennae short, with last segment tapered and slightly curved. The first flagellar segment is more than half as long as the second. In females, face broad, with eyes converging at the lower end. THORAX: Tegulae are narrowed at the front, as in Melissodes, though maybe not quite as strongly. The outer margin, at the front (anteriorly) is see-through and lacks punctation. WINGS: Base of the costal vein, which runs the length of the margin out to the stigma, is very large. LEGS: In females, scopal hairs are strongly branched. ABDOMEN: With hair bands of varying thickness; T1 often fully covered in hair. SIMILAR GENERA: The genus resembles Svastra and Melissodes. At the genus level, it can be difficult to distinguish from Melissodes; see Melissodes for distinguishing features. Svastra are bigger than Martinapis and have round tegulae, instead of strongly teardrop-shaped. Also, Svastra usually have flattened feathered hairs on T2, which are not seen in Melissodes.

— Martinapis luteicornis SIZE: Medium

to large; 12–17 mm. through August, with a few records into September. FLORAL HOSTS: Specialist on indigo bush (Psorothamnus), seen mostly in the early morning hours or at dusk. RANGE: Arizona, New Mexico, and western Texas. NESTING: Presumed ground nester. IDENTIFICATION: Fluffy bee, with stunning yellow antennae in males. HEAD: Clypeus sticks out far beyond the eye, with large well-spaced pits. In females, clypeus is black, antennae are light brown, and mandibles are dark yellow. In males, clypeus bright yellow, with a small brown spot to either side of center; mandible yellow as well. Also in males, antennae yellow, with the side facing the head brown. Long hairs stick out from the head next to compound eyes. THORAX: Covered in thick reddish to blonde hair. Tegulae are reddish. Scutum covered with small dense pits, hard to see. LEGS: In males, the PHENOLOGY: June

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Martinapis luteicornis (female)

Black scopal hairs

Martinapis luteicornis (male)

front femur is flattened, and broad at the middle. The hind margin is angled. The teeth of the mid and hind tarsal claws are long, with the hind claws being asymmetrical (one much longer than the other). In females, the scopal hair on the outer surface of the hind basitarsus is almost entirely black. ABDOMEN: Hair the same color as that of the thorax can be seen on T1. For T2–T4, there are sparse hairs, with short flattened hairs at the base of each segment. In males, T1 through T4 have small dense pits, especially near the base. Pygidial plate reddish. SIMILAR SPECIES: There are only two species of Martinapis in North America. See similar species under M. occidentalis for differences.

— Martinapis occidentalis SIZE: Medium to large; 11–16 mm. PHENOLOGY: March through April, with several records in September and October. FLORAL HOSTS: Generalist, visiting plants in the Asteraceae, Fabaceae, Solanaceae, and Zygophyllaceae families. RANGE: California east to southwest Arizona. NESTING: Ground nesting. IDENTIFICATION: Fuzzy bee with bright yellow antennae in males. HEAD: Eyes light green to blue, inner margins converging slightly. In males, the yellow clypeus is only moderately protuberant, with large sparse pits. Also in males, antennae are pale yellow, but black on the inner side of the scape. Mandible may be black or yellow. Though hard to see, the galea is short, about three-quarters the length of the compound eye. THORAX: Coated in long dense light gray to blonde hair. WINGS: Wing venation reddish.

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264  Apidae LEGS: The hind claws are even, with both being the same length. In males, the fore femur is slightly wide, with a round angled hind margin, and short flattened hair on the inside (very hard to see). In females, the scopal hair on the outside of the hind basitarsus is white or cream colored. ABDOMEN: The first tergal segment is covered in long thick hair that is the same color as that of the thorax. In females, the second through fifth tergal segments are covered with dark brown to black hair, and white basal and apical hair bands on T2 and T3, outlining the whole segment. In males, the white hair bands are mostly basal, with very little hair at the apex of each segment. The fourth tergal segment has even more white hair than T2 and T3. The pygidial plate is dark. SIMILAR SPECIES: Appears similar to M. luteicornis. The galea is shorter in M. occidentalis, and the hind tarsal claws are almost symmetrical in M. occidentalis, while they are asymmetrical in M. luteicornis. In males, Martinapis occidentalis White scopal (female) the clypeus of hairs M. occidentalis is less protuberant. In females, the scopal hairs are black in M. luteicornis, and white in M. occidentalis.

Martinapis occidentalis (male)

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MELISSODES — SUBFAMILY: Apinae — TRIBE: Eucerini OVERVIEW: Melissodes are fast-flying fall bees in which the males have extremely long antennae. Many are specialists on plants in the Sunflower family (Asteraceae). Melissodes females nest in the ground and may nest in aggregations. IN THE WORLD: Worldwide there are around 125 species, distributed almost entirely in the Western Hemisphere. Nearly 100 species occur in North America, and more than 80 are found in western and midwestern states. CLEPTOPARASITES: Triepeolus, Epeolus, possibly Melecta or Brachymelecta. IDENTIFYING FEATURES: Medium-sized bees that fly fast. HEAD: In males, antennae are long and often extend back at least to end of scutellum. The clypeus of males is pale or yellow. In both sexes, the first segment of the antennae is less than half as long as the second segment. The maxillary palpi, on the mouthparts, are four-segmented (this is hard to see without a microscope). Head is completely flat at the top, with the vertex extending so straight behind the compound eyes that the ocelli appear almost to stick up above it. THORAX: Tegula is teardrop-shaped, tapering to a point at the anterior end (this can be very hard to see and may require the removal of hair from the region with the tip of a pin). WINGS: Marginal cell is long, curving gently away from the wing margin, and the entire surface, even inside the cells, is covered with minute stiff hairs. LEGS: Scopal hairs may be branched or simple but are thick. On the abdomen, bands of hair often run across each tergal segment. In many species the hair on the fourth tergal segment is separated in the middle, giving the band a notched look. In males, there is a small tooth to either side of the pygidial plate. SIMILAR GENERA: Eucera, Martinapis, and Svastra are other Eucerini that look very similar to Melissodes species. Of these, only Melissodes have teardrop-shaped tegulae, much narrower anteriorly than posteriorly (but see Martinapis below). They also have four-segmented maxillary palpi; Eucera do not have four-segmented maxillary palpi. In Eucera, the clypeus usually sticks out substantially from the face. In Svastra, some species have four-segmented palpi. They tend to be larger bees, though, with broad thick hair bands on the abdomen, and flattened, branched hairs frequently intermixed with other hairs. In Martinapis males, the tegulae approach a similar teardrop shape, though not quite as constricted anteriorly. The first flagellar segment in males is more than twice as long as the second. In Melissodes males, both the first and second (and sometimes third, etc.) are elongated. With females, the mandible of Martinapis stays broad, not narrowing to one point as in Melissodes, and the final flagellar segment is twice as long as it is wide; in Melissodes it is much shorter. Melissodes can be very difficult to distinguish, and keys that include all western species have not been published. Verify your identifications against a reference collection.

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— Melissodes agilis SIZE: Medium;

11–15 mm. June through

PHENOLOGY: Late

September. FLORAL HOSTS: Specialist on Asteraceae, especially Helianthus (sunflowers). RANGE: Widespread across the U.S., ranging into southern Canada; arguably the most common species of Melissodes in the U.S. NESTING: Ground nester, often in aggregations near where patches of sunflowers are growing. IDENTIFICATION: Common species across the U.S., with light red hair, and a preference for sunflowers. HEAD: Hair on head pale to light auburn, thick and dense. Clypeus more or less flat, protruding only slightly from head. Black in females, but female mandibles have small yellow spot at the apex. In males, the clypeus is yellow and the Integument is translucent at labrum is yellow, rimmed with a Thick auburn hair the apex of each darker color, and only the base of on the head and tergal segment. thorax the mandible is yellow. Gena narrower than the width of the compound eye. Antennal segments brown to tan below, in males exceedingly long, extending over the back of the scutum to the scutellum; yellow to red, with brown on the surface that faces the head. Melissodes agilis THORAX: Thick erect light (female) auburn hair covers scutum, scutellum, and metanotum, as well as the sides of the thorax. Beneath hair, the scutum is densely pitted. WINGS: The veins are reddish brown.

Melissodes agilis (male)

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Integument is translucent at the apex of each tergal segment.

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x .

Melissodes  267 LEGS: In

females, scopal hairs are light brown to yellow, dense, and very feathery. both sexes, the integument is translucent at the apex of each tergal segment. In females, T2 and T3 have thick erect black hairs, but with a band of thick light brown to yellow hair running across the middle. The first tergal segment has light auburn hair covering the anterior face. The fourth tergal segment is nearly all light auburn hair. On the fifth, all hair is dark. In males, pubescence is lighter, and sparser, forming broad loose light bands of hair on T1–T5 that do not always appear bandlike. SIMILAR SPECIES: Though common, and not variable in appearance, there are a few western species that resemble M. agilis. Melissodes perlusus, found in the southwestern U.S. and also specializing on Helianthus, appears similar; in females of M. perlusus the tergal segments are more finely pitted, and in males, the bases of the mandibles are black. Melissodes submenuachus, found only in New Mexico and Arizona, also appears similar. In that species, the clypeus has coarser punctation in females, and a narrower clypeus. ABDOMEN: In

— Melissodes tristis SIZE: Medium; 9–14 mm. PHENOLOGY: March through November, with peak abundance in early May, mid-July, and early September. FLORAL HOSTS: Generalist. RANGE: Found throughout the southwestern U.S.; Nebraska south to Mexico, west to California. Absent from the Pacific Northwest. NESTING: Ground nester; may have up to three generations per year in southernmost states. IDENTIFICATION: Fast-flying gray bee, often with long antennae and blue eyes. Seen commonly throughout the flowering season. HEAD: Wide face, with pale bluish-green compound eyes slightly converging. Lots of pale hair covers most of the surface. In both sexes, the clypeus is flat, not protruding notably from the head. In females, the clypeus is very wide, with a shiny spot at the center. In males, it is narrower, and completely black. Also in males, the antennae are extremely long. THORAX: Covered in Melissodes tristis off-white hair. ABDOMEN:  (female) In females, T1 has a broad, translucent, hairless apical

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T1 has a broad translucent apical margin.

T2 hair band is interrupted by a black band, making it look like T2 has two hair bands.

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margin, and the base has very small and shallow pits. The second through fourth tergal segments often have red areas at the apex. In females, scopal hairs are light colored. White hair bands, Melissodes tristis (male) slightly appressed, run across T2 and T3. In females, on T2 the hair band is interrupted, so that it looks like there are two hair bands, one at the base, and one just above the apex. On males, T2 has a hair band that runs across the center only. In both sexes, T3 has a hair band that runs across the center. SIMILAR SPECIES: Female M. tristis appear similar to M. coreopsis. In females, M. coreopsis has a narrower clypeus, without a central shiny area, and much denser pits on T1. In males, the entirely black clypeus of M. tristis (which is distinctive among Melissodes) separates it from any other species.

— Melissodes paroselae SIZE: Small

to medium; 9–10 mm. through September. FLORAL HOSTS: Seen nectaring from many flowers, but appears to specialize on Fabaceae, especially Melilotus (sweet clover). RANGE: Northern Utah south to the Mexican border. Texas west to southern California. NESTING: Ground nester. IDENTIFICATION: Striking midsized Melissodes. Females have an orange collar and stark white-and-black hair bands on the abdomen. HEAD: In males, antennae are bright orange. The clypeus, labrum, and basal half of the mandibles are bright yellow. White hair covers head, but the vertex is auburn. THORAX:  Scutum with short auburn hair, appearing slightly flattened. The scutellum has dense black hair. The sides of the thorax have all light hairs. Pits on scutum and scutellum PHENOLOGY: June

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Melissodes  269 Antennae orange Melissodes paroselae (male)

Scutum with short auburn hair

Melissodes paroselae (female)

are deep and distinct, very coarse. WINGS: Veins are dark red brown. LEGS: The tarsal segments are red. In females, the hairs on the inner surface of the hind basitarsus are red to yellow. T1 covered with long white hair ABDOMEN: In females, T1 with long sparse white hair; integument is dark, but the apical margin is translucent. Also, T2 has a basal band of white hair, and a band running across the center. Dark stout hair T2 has a basal hair separates the two. Under a microscope, the band and a thin band Scutellum with running across the pale hair band at the base of T2 can be seen dense black hair center of the segment. to have feathery and flattened feathery hairs mixed together. Tergal segment 3 has a basal band of white hair. In males, white hair bands are all apical, with dark hair on the base and middle of each tergal segment. In both sexes, few pits occur in the apical areas of T2 and T3, so they appear shiny. SIMILAR SPECIES: Appears similar to M. grindeliae, but the antennae in males are longer, and M. grindeliae does not have red tarsal segments. Also appears similar to M. communis. The flattened, feathery hairs on T2 in females will separate the two. Also, M. communis usually has dark hairs on the sides of the thorax, and the clypeus extends outward from face more than in M. paroselae. Males are trickier. In M. communis, T5 is usually missing a pale hair band, which is often present in M. paroselae. Finally, M. glenwoodensis may appear similar because of the reddish hair. That species is larger, however (11–15 mm), and more common on Asteraceae.

— Melissodes dagosus SIZE: Medium; 10–12 mm. PHENOLOGY: June through August. FLORAL HOSTS: Unknown, but frequents Fabaceae. RANGE: Colorado west to the Sierra Nevada. Washington south to Arizona. NESTING: Presumably ground nesting.

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IDENTIFICATION: Fluffy medium-sized bee with striking white hair bands on abdomen. Males, which have a yellow clypeus, have short antennae. HEAD: Black, with silky white hair in abundance. Eyes appear pale green and converge strongly toward the mandibles; they are about as wide as the gena. The clypeus does not protrude significantly from face. In males the clypeus is bright lemon yellow, as is the labrum at its center, and a small spot on the mandibles. Also in males, antennae are short, with no wavy edges, red-orange on the side facing the head (short antennae are uncommon in male Melissodes). THORAX: Dark, with white hair. In females, punctation on the back half of the scutum is very sparse. LEGS: Dark, with thick hair. Tarsal joints are red. In females, scopal hairs are sparse, lightly feathered, and do not obscure the surfaces of the hind basitarsi and tibiae. Scopal hairs are sparse, lightly feathered, and do not In males, hair on inner side obscure the surfaces of the White hair of hind basitarsus is orange. hind basitarsi and tibiae. on the head ABDOMEN: Distinctive white and thorax hair bands, all about the same thickness, on apical margins of tergal segments. Tergal segments are covered in relatively dense pits, separated by less than the diameter of one pit. In males, the last exposed Melissodes dagosus tergal segment has small teeth on (female) either side of the pygidial plate. SIMILAR SPECIES: Similar Melissodes dagosus (male) to M. lupinus and M. agilis. The short antennae in males are distinctive. In females, M. agilis tends to be much redder, and without the distinctive hair bands. With M. lupinus, the Last tergal segment Clypeus hair bands are more variable in has small teeth on either bright yellow side of the pygidial plate. thickness, becoming thicker toward

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Melissodes dagosus (female)

White hair bands on apical margins of tergal segments

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Melissodes  271

the posterior end of the bee. In addition, M. lupinus females are the only Melissodes species with the last flagellar segments so incredibly short, usually wider than long. And finally, the scopal hairs of M. lupinus are plumose only at their apices, which are bent.

— Melissodes stearnsi SIZE: Small

to medium; 8–11 mm. early as April and as late as September, but most common between June and August. FLORAL HOSTS: May be a specialist on Asteraceae (the Sunflower family) or on Polemoniaceae—the special hairs on their galea may be an adaptation to this. But they have been observed visiting a wide variety of flowers; males are frequently seen nectaring on Asclepias (milkweed). RANGE: West Coast; British Columbia, Washington, This bee is often seen on Asteraceae Oregon, and California but has adaptations for visiting Polemoniaceae. One theory is that this into Baja. NESTING: Short appressed hairs over the entire surface bee has recently switched pollen hosts and Ground nesting. of the abdomen so still retains the traits associated with IDENTIFICATION: Relatively collecting pollen from Polemoniaceae. small Melissodes with pale to reddish hair and striking pale blue eyes in living specimens. HEAD: Dark integument, pale light blue eyes, and pale to yellowish hair. The clypeus is flat, not protruding beyond the eyes. In females, clypeus sometimes has a reddish tint and Melissodes stearnsi Scopal hairs are white large, slightly elongated pits toward (female) and very feathery. the apex. Also in females, flagellar segments are longer Melissodes stearnsi than broad. Though hard to see, (male) in females the hairs on the galea (the big sheaths that surround the inner glossa, or tongue) are long and strongly hooked. In males, the clypeus and base of the mandible are pale yellow. THORAX: Hair on thorax is pale yellow to white, trim and even in length. The scutum has deep round pits, crowded toward the edges, but sparse near the center. LEGS: In females, scopal hairs T1–T5 translucent at the apex are white, and very feathery. PHENOLOGY: As

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272  Apidae ABDOMEN: In females, the integument on T1–T4 is often reddish brown at their apices. The base of T1 has long pale hairs, but T2 has dense white hair at its base, with the apical area having only a few appressed white hairs. On T3 and T4, the dense basal hair is present, but there are also short appressed hairs over the entire surface. In males, the apex of T1–T5 is translucent. Also in males, though hard to see, the apical margins of S2–S4 are drawn out into broad translucent extensions. On S4 the extension is as long as the basal part of the sternum; on S2 and S3 it is bilobed. This is a character unique to males of this bee. SIMILAR SPECIES: This species appears similar to other bees in the subgenus Callimelissodes, including M. lupinus and M. clarkiae, whose range it shares. Its most distinctive characters are hard to see without a microscope (hooked hairs on galea and long translucent flaps on S2–S4 in males). The lighter color of clypeus can narrow the list of similar species; M. stearnsi males never have a yellow clypeus. In females, the short pale hairs covering T2–T4 are unique; most species are not covered as completely with short white hairs. And on T5 and T6 there are longer dark yellowbrown hairs. In most similar species T5 and T6 have darker brown hairs.

SVASTRA — SUBFAMILY: Apinae — TRIBE: Eucerini OVERVIEW: Large fast-flying bee with a lot of hair, which is often strikingly colored. Scopal hairs are robust, and wings are often smoky. Many species are specialists (Helianthus, Oenothera, Ferocactus). Ground nesters, sometimes in small aggregations. IN THE WORLD: Twenty-three species worldwide, all found in the Western Hemisphere; more than 20 of these are found north of the equator. In North America there are 16 species; 15 of which occur in western states and provinces. CLEPTOPARASITES: Triepeolus. IDENTIFYING FEATURES: Large, fuzzy summer bees usually seen rummaging on their preferred plants. HEAD: Malar space is almost nonexistent; there is very little space between the eye and the beginning of the mandible. The clypeus is relatively flat. In males, the antennae are long, but not overly so, ending near the back of the thorax. In males and females, the first flagellar segment is less than half the length of the second one, but longer than it is wide. THORAX: The tegulae are oval-shaped. The propodeum has a large dorsal face. On the metanotum there is often a tuft of hair that is longer than the hair around it. ABDOMEN: There are basal hair bands on T2 and often T3 and T4, and these are covered with branched hairs, the branches of which are slightly flattened. SIMILAR GENERA: Melissodes are closely related and share a similar appearance, though they are smaller on average than Svastra. Antennae in male Melissodes are longer than in male Svastra. In both sexes, Melissodes have a clypeus that sticks out further in profile. Melissodes have tegulae that are egg-shaped, narrower at the anterior end than at the posterior end. Hair bands on abdomen of Melissodes are more pronounced. Eucera also

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appear more similar, but do not overlap much with Svastra, which fly in summer and fall, while many Eucera are spring bees. Eucera do not have the flattened, feathery hairs on T2 that are found on Svastra.

— Svastra duplocincta SIZE: Medium; 10–12 mm. PHENOLOGY: June through September. FLORAL HOSTS: Specialist on barrel cactus (Ferocactus) but may visit other composites as well. RANGE: From southern California east along the U.S.-Mexico border to Texas; dry deserts where barrel cactus are common. NESTING: Nests in the ground, but may nest communally, with 10–20 females sharing the same nest entrance. Nest may be reused for multiple years. IDENTIFYING FEATURES: Smaller Svastra that can appear very similar to Melissodes. Most commonly found rummaging in the bright orange pollen of barrel cactus flowers. HEAD: Eyes bulge out from sides of head; wide but short, so that it is less than twice as long as its widest part. Clypeus flat at the end closest to the antennal sockets but protruding out in front of the eyes at its lower end; protruding more in males than females, but still flat at the end closest to the antennal sockets. In males, antennae are long, reaching beyond scutum and scutellum, but first flagellar segment only about a third the length of the second flagellar segment. THORAX: In both sexes, dense white hairs at the junction of the scutum and the scutellum are branched at their bases and flattened at their tips; while distinctive, these can be hard to see without a microscope. Metanotum Svastra duplocincta (male) has a thick tuft of hairs at its center. LEGS: In females,

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Svastra duplocincta (female)

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midtibial spur bent sharply at its tip. Scopal hairs white, thin, and very branched. ABDOMEN: Hairs on T2 are white, branched at their bases, and flattened at their tips. In females, the pygidial plate is V-shaped; in males, it is more squared off. In males, on the sides of S3 and S5 the hairs are hooked, and curve into the center. SIMILAR SPECIES: This is the only Svastra that specializes on cactus, which can help with identification. The patterning of the branched/flattened hairs (dense on the scutellum, thick on T2) is unique, as is the shape of the clypeus, which is flat on its top but bulges at the bottom. Svastra duplocincta may look more like Melissodes than other Svastra; the shape of the tegula (which are teardrop-shaped in Melissodes) can help, on pinned specimens. In the field, the longer antennae in the males and sparser hair on the scutellum in both sexes may help.

— Svastra obliqua SIZE: Medium

to large; 14–16 mm. through September. FLORAL HOSTS: Specialist on sunflowers (Helianthus) but may visit other composites as well. RANGE: From California to New York, largely absent from the Northeast. Less common in northern states, though occasionally found in southern Canada. NESTING: Solitary, nests in the ground, preferring bare dirt. Often nests in aggregations, and several females may share a nest entrance. IDENTIFYING FEATURES: Large bee with copious hair, contrastingly colored across the body. There are two distinct color forms of S. obliqua. One is nearly all dark, while the other has patches of both light and dark hair. Both are described here. HEAD: Eyes are large, wider than the genal area. In males, the clypeus is bright yellow. THORAX: The scutum is covered in coarse punctation and thick tawny hair, which fades to black at the posterior end. In females, the sides of the thorax are dark in color. In males, the sides of the thorax are tawny in color. WINGS: Dark and smoky. LEGS: In males, the inner surface of the hind basitarsus is covered with dark rust-colored hairs. In females, scopal hairs are highly feathered, and pale in color. ABDOMEN: In females, T2 has a band of tawny appressed hairs running across the middle of the segment. The third tergal segment has a hair band comprising simple hairs that narrows toward the midline but does run across the middle of the segment. The fourth tergal segment has a thick light-colored hair band, with no interruptions. The pygidial plate is V-shaped. In males, bands run evenly across each tergal segment, midway through the segment. Also in males, T7, if visible, lacks lateral spines. SIMILAR SPECIES: Three subspecies exist: S. obliqua caliginosa is a darker form, slightly larger (15–17 mm). It occurs in the East. Svastra obliqua obliqua is lighter, with prominent bands of pale hair on the abdomen. Svastra obliqua expurgata is the most common variant in the West. PHENOLOGY: July

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Anthophora  275 Svastra obliqua expurgata is lighter and is more common west of the Rocky Mountains.

Svastra obliqua obliqua is a darker subspecies that is more common in the Midwest.

Svastra obliqua expurgata (female)

T4 with thick complete hair band Svastra obliqua (male)

ANTHOPHORA — SUBFAMILY: Apinae — TRIBE: Anthophorini OVERVIEW: Conspicuous fast-flying bees, medium to large in size. Often hover in front of flowers, tongue extended, adjusting their legs. The thorax is hairy, and hair may be black, red, or (most commonly) gray. Seen in late spring through fall. Almost all Anthophora nest in the ground or in vertical banks (see A. terminalis for an exception), either in aggregations or singly. Some Anthophora construct small mud chimneys over their nest entrances. IN THE WORLD: There are more than 400 species found around the world, mostly in the Northern Hemisphere. Nearly 60 species occur in the U.S. and Canada, and nearly all of them can be found in the West. CLEPTOPARASITES: Melecta, Zacosmia, Brachymelecta, Triepeolus. IDENTIFYING FEATURES: Anthophora are medium to large hairy bees that fly remarkably fast. Typically gray in color, they collect pollen on their hind legs. HEAD: The vertex appears flattened, not rounded (as in Emphorini). In males there are extensive yellow or white markings on the clypeus and often also the antennal scapes and/or the mandibles. WINGS: Three submarginal cells and, importantly, the first recurrent vein intersects the second submarginal cell near the middle. The wings are bare in the veined area (the cells are bare), but very hairy at the edges. The third submarginal cell in Anthophora is more or less square (compare with Habropoda). LEGS: In males, there are often modifications, like long brushes of hair. Both males and females have arolia. SIMILAR GENERA: Habropoda look so similar to Anthophora that wing venation is the only certain way to distinguish them. In Habropoda, the first recurrent vein intersects

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exactly at the junction of the second and third submarginal cell, creating a + sign on the wing. The third submarginal cell is fairly curved at the posterior end. Bombus females also look similar, but collect pollen in corbicula, not in scopal hairs. The faces of Bombus tend to be longer, and males (which are less commonly seen) do not possess yellow coloration. On the hind wing, Bombus lack a jugal lobe. Melissodes and other Eucerini may seem similar in size and hairiness. The antennae of male Eucerini are significantly longer than in male Anthophora. Also, the Eucerini have small hairs on the wings while Anthophorini wings are hairless in the area where the veins are.

— Anthophora bomboides SIZE: Medium; 12–15 mm. PHENOLOGY: April through July. FLORAL HOSTS: Generalist. RANGE: Anthophora bomboides ranges across the U.S., with various subspecies found in different regions. NESTING: Gregarious nester with records of several hundred bees nesting in a square meter. Often nests in vertical banks. IDENTIFICATION: Anthophora bomboides shows great variation in the color patterns of the thorax and especially the abdomen. Individuals may exhibit yellow, red, orange, or tawny hair on any or all of T1–T4, depending on the individual and the subspecies (see similar species for descriptions of hair color patterns). HEAD: The clypeus is strongly protuberant. The gena is the same width as the eyes. Males have a yellow clypeus, yellow scapes, and a small bit of yellow beside the clypeus. In females, the clypeus is black, polished, and shiny between pits. THORAX: Scutum shiny with large pits. WINGS: Slightly cloudy. LEGS: Scopal hairs on hind tibia are black. Anthophora bomboides ABDOMEN: In males, there is no pygidial plate. (male) SIMILAR SPECIES: Five subspecies of Anthophora bomboides are sometimes recognized. Anthophora b. sodalis occurs from the Midwest west to California and north to Canada. In this subspecies, the thorax and T1–T3 (and sometimes T4) are covered Yellow clypeus that sticks out from the face with red hair. It intergrades with A. b. solitaria, which has a red scutum, but a black metanotum, and red on T1–T3. That subspecies

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Anthophora  277 Anthophora bomboides sodalis is

can be found in a subspecies common from the Midwest to California. Washington and British Columbia. Anthophora b. stanfordiana can be found from California north through Oregon. In this subspecies, T2 is yellow, while T3–T7 have yellow and black hair intermixed. Finally in the West, there is A. b. aterrima, which looks similar to A. b. stanfordiana; in females they are all black, while males have a few pale hairs on the face and the scutum. This is the least common form, occurring in a limited area of California. Anthophora abrupta always has an ochraceous thorax and all-black abdomen, while A. bomboides varies in color, but never has the same combination as A. abrupta. Anthophora occidentalis also looks similar, but is entirely ochraceous, unlike A. abrupta.

Anthophora bomboides (female)

Scopal hairs are black.

Anthophora bomboides stanfordiana is a subspecies common along the Pacific Coast.

— Anthophora californica SIZE: Medium; 10–13 mm. PHENOLOGY: June through August. FLORAL HOSTS: Generalist. RANGE: California and Oregon, east to Louisiana, north to Colorado, Oklahoma, Nevada, mostly in drier habitats. NESTING: Ground nester; in areas with long flowering seasons and late-summer rains, there are two generations in a year. IDENTIFICATION: Gray bees with striking green eyes. HEAD: In living specimens, the eyes have a green hue. They converge slightly toward

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Live specimens have bright green eyes. Anthophora californica (female) Integument is white

at the apex of each lower half of face and bulge abdominal segment. out from the head. In males, clypeus, mandibles, area above and Anthophora californica (male) areas beside clypeus bright yellow. Undersides of the scapes are also bright yellow. THORAX: Scutum with white to light tan hairs; a few dark hairs are mixed in. LEGS: In males, the tibia and tarsal segments are red. On the hind tibia there is a spine, and on the spine there is a small tooth that angles Tibia and tarsal segments are red. forward and slightly in. Right next to the spine on the hind tibia, there is a tooth aimed anteriorly. In females, scopal hairs are white. ABDOMEN: On the abdomen, the integument is white at the apex of each segment. Some white hairs are also present apically. In females, T1 is covered with long white hairs. SIMILAR SPECIES: Appears most similar to A. montana. Anthophora californica has lighter hairs on T4 than does A. montana, where the two are more evenly mixed, to all dark. Similarly, hair on the face, scutum, and sides of the thorax are lighter in A. californica.

— Anthophora terminalis SIZE: Medium; 10–13.5 mm. PHENOLOGY: Early June through September. FLORAL HOSTS: Generalist, visiting a wide variety of plants for pollen and nectar, but may have preference for those with long corolla tubes. RANGE: Occurs across the U.S. In the West, can be found across the Rocky Mountains to the coast. Occurs as far north as Alaska and the Northwest Territories. NESTING: These are the only Anthophora that nest in excavated cavities instead of in the ground. They can be found in beetle burrows in rotting logs and inside larger plant stems.

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IDENTIFICATION: Large, fast-flying, dark bee. The thorax and abdomen sport light gray hair, through which the integument can be clearly seen beneath. HEAD: The gena is narrower than the width of the compound eye. In males, the clypeus is all yellow, and the yellow runs up above the clypeus to the antennal sockets, as well as in a strip next to each compound eye. The scapes and mandibles are black. THORAX:  Light straw-colored hair intermixed with black covers the thorax. ABDOMEN: Tergal segments have bands of short white hair at the apex of each. In females, the end of the abdomen has bright orange stiff hairs that are visible in flight or as they burrow into flowers. SIMILAR SPECIES: May appear Anthophora terminalis similar to A. abrupta and (female) A. bomboides as they are similar size and fly at the same time. The orange tip is unique to female A. terminalis, and the antennal scapes of male A. terminalis Thorax and abdomen with light gray hair, lack yellow, which is seen in with black integument males of the other two species. easily seen beneath

The tip of the abdomen has a row of bright orange hairs. Anthophora terminalis (male)

— Anthophora urbana SIZE: Medium;

10–13 mm. PHENOLOGY: Late May through July. FLORAL HOSTS: Generalist. U.S.; Colorado and Texas to the Pacific Coast, including southern Saskatchewan. Usually in lower xeric regions but can be found in some high-elevation areas. NESTING: Ground-nesting species. RANGE: Western

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IDENTIFICATION: Larger gray-andblack-haired bee with white stripes on the abdomen. HEAD: In living specimens, the eyes are a bluish color. Black and gray hairs are intermixed on the frons and vertex. The vertex is relatively flat, with eyes not significantly raised above the flat line that defines the top of the head when viewed from the front. In females, the clypeus is all black, flattened, and the center has deep widely spaced pits. Also in females, the first flagellomere is about as long as the next 2–3 taken together. In males, the clypeus is all ivory, as is a small area above the clypeus, the areas beside the clypeus, the labrum, and the underside of the scape. In both males and females there are long white hairs below the face. THORAX: Coated in mostly white to gray hair, with some black intermixed. WINGS: Marginal White and black hair cell much shorter than the first submarginal intermixed on thorax cell. LEGS: In males, hind tibia is whitish, with no projections. Also in males, there are brushes of hair on the midtarsal segments. In females, scopal hairs are white. ABDOMEN: On the abdomen, there are bands of thick white hairs. The male has only black on T2. Also in males, there is no pygidial plate. Anthophora urbana The first tergal segment is the same color as the thorax.

(female)

Anthophora urbana (female)

White stripes of hair on abdomen–the integument beneath is black.

Anthophora urbana (female)

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Anthophora  281 Anthophora urbana (male)

SIMILAR SPECIES: Anthophora urbana has bands of thick white hair on the Hind tibia light, abdomen across each tergal segment. Other and covered with light hair Anthophora with thick white bands typically have integumental bands instead (e.g., A. californica, A. montana males, and A. marginata females); this helps distinguish.

— Anthophora affabilis SIZE: Medium;

11–12 mm. in the year than many Anthophora; seen from March through July. FLORAL HOSTS: Generalist. RANGE: Midwest west to the Sierra Nevada, but absent from the western side of this range. NESTING: Ground nester. IDENTIFICATION: Larger gray bee; males hover near plants they defend from other males. HEAD: With light hair, no black intermixed; the hair is redder in males. In males, the clypeus Most of the hair on is yellow, as are the areas beside the the thorax is light blonde/grey. Anthophora affabilis clypeus, above it, the labrum, and (female) the scapes. THORAX: Covered in copious light-colored hair, may be orange/red in males. LEGS: In females, scopal hairs are white. In males, there is no mid-basitarsal brush, though there are slightly longer hairs at the distal end of the tarsi. Tibial spurs are dark. ABDOMEN: The first tergal segment is covered in copious light hair. The second is a mix Minimal white of light and dark hairs, with mostly dark, striping on apex and some white near the base. The apices of tergal segments PHENOLOGY: Earlier

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of T2 and T3 have a thin band of white hairs, thinner in the middle. In males, there is a pygidial plate. SIMILAR SPECIES: Appears similar to A. porterae, but that species has more of a mix of black and pale hairs on the scutum, appearing darker than A. affabilis. Anthophora affabilis (male)

— Anthophora curta SIZE: Small; 8–10 mm. PHENOLOGY: June through September; probably bivoltine throughout most of its range. FLORAL HOSTS: Specialist on Asteraceae. RANGE: Southwestern U.S., rarely found as far north as the Pacific Northwest. NESTING: Ground nesting. IDENTIFICATION: Small Anthophora; fast flyer with green eyes and appressed hair on tergal segments. Small Anthophora (less than 10 mm) in the U.S. are in the subgenus Micranthophora. HEAD: The clypeus has a band of yellow to yellow green at its apex, and the mandibles are yellow. In females, labrum is yellow, and the clypeus is extremely flat. Also in males, there is no yellow on the scape. THORAX: The scutum is shiny, with This Anthophora is much smaller no densely pitted areas. WINGS: No than others featured in this book. small hairs in the first submarginal cell. LEGS: Midtibial spur unmodified, light colored, curving gradually to an abrupt hook. ABDOMEN: There are apical bands of appressed hair on T1–T4, extending to T6 in Hair bands on abdomen are males. In females, the appressed. basitibial plate has a straight edge. In males, though hard to see, on T7 there is a projection at the center. Anthophora curta (female)

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SIMILAR SPECIES: Among the 26

Anthophora (Micranthophora) species in the Western Hemisphere, this is arguably the most common one in the U.S. The black antennae in males, and the flat clypeus in females are distinctive, as are the characters on T7 in males, and the basitibial plate in females, though these are best seen with a microscope.

Notice that the scape is not yellow in this male.

Anthophora curta (male)

— Anthophora pacifica SIZE: Medium; 11–12 mm. PHENOLOGY: April through June. FLORAL HOSTS: Generalist, but common on manzanita (Arctostaphylos). RANGE: West Coast north to British Columbia. Absent from the Great Basin but found throughout the Rocky Mountains and south to Arizona and New Mexico. NESTING: Ground nester. IDENTIFICATION: Larger all-black fuzzy bee, females with white scopa. HEAD: Females have a black clypeus. All hair on the head of females is black. In males, the clypeus is yellow, as are the labrum, and the undersides of the scapes. Hair is a mix of white (mostly around the clypeus), and white-with-black on the vertex. THORAX: In females, hair is all black. In males, the thorax has The white scopal a mix of white and black hair. hairs are a wonderful LEGS: In females, the scopal hairs contrast to the dark hair on the rest of Anthophora pacifica are white, in strong contrast to the the female’s body. (female) dark hair on the rest of the body. In males, middle tarsi with a long white fringe of loose hair on the posterior side, becoming dark near the basitarsus. Also in males, the midtarsal joint has no fringes on the sides. ABDOMEN: In females, hair is all black, and sticks up. In males, white hair is most common on T1 and T2, while black predominates on T3–T4. SIMILAR SPECIES: No western female species has the black hair with white scopal hairs seen in female A. pacifica.

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Anthophora pacifica (male)

Middle tarsi with a long white fringe of loose hair on the posterior side More black hair on T3 and T4, lighter hair closer to thorax

No clear white bands on the abdomen

HABROPODA — SUBFAMILY: Apinae — TRIBE: Anthophorini OVERVIEW: Habropoda is a genus of large bees (12–16 mm) commonly seen throughout the West in the early spring. Habropoda nest in the ground, usually individually, but they are sometimes found in aggregations. Many of them are oligolectic, collecting pollen from only one or two flowering plant genera, or just one family. IN THE WORLD: Worldwide, there are more than 50 species, split between northern regions of the Eastern and Western hemispheres. In the U.S. and Canada there are 21 species; 20 of them are found in western states and provinces. CLEPTOPARASITES: Most commonly Melecta, but also Brachymelecta. IDENTIFYING FEATURES: Habropoda are large fuzzy bees that usually fly in the spring (see Habropoda excellens, though). In overall appearance, they resemble Anthophora to such an extent that wing venation may need to be used to distinguish them (see similar genera). HEAD: Between the compound eyes, the vertex is very flat. In males there are often significant yellow or white markings on the clypeus, the antennal scape, and even the mandibles. THORAX: Often hairy. Tegulae are rounded, and more or less symmetrical. WINGS: Three submarginal cells. The first recurrent vein meets the line dividing the second and third submarginal cells straight on, forming a + or an X. The wings are bare in the veined area, but very hairy at the edges. LEGS: In males, there are often modifications, like long brushes of hair. Both males and females have an arolium. ABDOMEN: Variously hairy, but often the color of T1 matches that of the thorax. SIMILAR GENERA: Anthophora species, which are in the same tribe, look remarkably similar, and it may require a microscope to be certain of identity. In Habropoda, the vein that forms the edge of both the second and third submarginal cells meets the first recurrent vein squarely on, forming a + sign. In Anthophora, the first recurrent vein meets the middle of the second submarginal cell, forming a T instead. Habropoda tend to fly earlier in the year. Bombus are large and hairy but lack yellow faces (as seen in

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male Habropoda, and female Habropoda pallida). At the time of year when Habropoda are flying, the most common bumble bees seen are queens, which are significantly larger than female Habropoda. Habropoda do not have yellow or orange hair bands on the abdomen. Eucera are also fuzzy and big. The scopal hairs of Eucera that fly at the same time are longer than those of most Habropoda. Their wings are hairy throughout, rather than just outside the veins. And male Eucera have very long antennae. There is no modern key to western North American Habropoda species, so distinguishing between them can be challenging. We have included here several species that are common or very distinctive, but species identifications should be regarded as tentative without a reference collection with which to compare specimens.

— Habropoda depressa SIZE: Medium;

12–14 mm. through June; earlier months in coastal environments. FLORAL HOSTS: Generalist, collecting pollen from a wide variety of flowers, including oak catkins. RANGE: Common in California, but may range occasionally further east or north. NESTING: Ground nester in hardpacked soils (like clay); has also been found tunneling off walls in rodent burrows. Females do not sleep over in their nests at night but “roost” nearby. Some lineages reuse the same nest site for multiple years. This species may bet-hedge, with only some individuals from the previous year emerging each spring. IDENTIFICATION: Gray-haired fast-flying bee. HEAD: In females, integument is black; there are gray hairs mixed with some black on the vertex. The clypeus is heavily pitted. In males, the scape, the clypeus, the base A mix of white and black of the mandibles, and narrow lines hairs cover the thorax. next to the compound eyes Habropoda depressa (female) are white. THORAX: Covered in thin pale hair, intermixed with black hair. Scutum is covered with shallow, small but dense pits. LEGS: Hairs on legs are pale. Females have PHENOLOGY: February

Notice that on a Habropoda wing, the second submarginal crossvein and second recurrent vein almost meet to form an X, and there are no hairs inside the cells on the wing.

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Appressed tan hairs are intermixed with longer lighter hairs on abdomen.

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286  Apidae Habropoda depressa (male)

long, light scopal hairs on the hind tibia and basitarsus. ABDOMEN: The integument is brown and black. On T1, there are white hairs that stand up covering the entire surface except for the apical rim, where the hairs are black. On T2–T4, tan matted hairs cover the surface of each segment, in some specimens lighter, longer hairs are intermixed. In males there are fewer appressed hairs; they appear shaggy with light and dark hairs intermixed (similar to scutum). In females, the sternal segments have long white hairs laterally that appear similar to scopal hairs. SIMILAR SPECIES: Habropoda miserabilis occurs in many of the same areas and has a similar overall appearance. The hair on the abdomen of this species is erect, rather than matted, and the scape in males is black. On T1 especially, there are no intermixed black hairs, as in H. depressa. In addition, H. miserabilis is found nesting in sandy coastal dunes. Habropoda dammersi also looks similar, but the light hair on T2–T4 stands up, rather than being flattened, and on the faces of males, the markings are a darker yellow in H. dammersi, instead of whitish. In females of H. dammersi, there is a small yellow spot between the clypeus and the inner margin of the compound eye, which never occurs in H. depressa. Yellow patches on head of male

— Habropoda excellens SIZE: Medium to large; 14–16 mm. PHENOLOGY: Fall, August through early October. FLORAL HOSTS: Frequently seen on Chrysothamnus and Ericameria; may be a specialist. RANGE: California east to Utah. NESTING: Presumed to nest in the ground. IDENTIFICATION: Rare, and strikingly colored, large blonde bee. HEAD: Densely clothed in light yellow or blonde hair, fading to white on gena. In males, scape is inflated and flattened, yellow on the ventral surface, or the surface facing away from the bee. Flagellar segments are otherwise black. Also in males, clypeus, most of mandible, paraocular area, and supraclypeal region (just above the clypeus) are all yellow white. THORAX: Covered in thick, short golden hair; hair fades to pale on the underside of the body. Scutum is covered in fine dense pits, slightly dulled through the thick hair. In males, the hair is slightly less dense and more orange than

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Habropoda excellens (female)

Scape is inflated and flattened, yellow on the ventral surface.

Scopal hairs are orange.

The hair patterns on the abdomen of this species are remarkable.

Habropoda excellens (male)

in females. LEGS: In females, scopal hairs are on the tibia and basitarsus, and are orange, more so on inner surface of hind basitarsus. In males, femur and tibia on all six legs are swollen, and very stout. The tibia is covered in thick, short white hair. ABDOMEN: Hair on T1 is the Habropoda excellens same color as the thorax. The patterning on (male) T2 through T4 is unique; a black triangular area runs down the center of each segment, and to either side of center, there are two black Femur and tibia are lobes, creating a distinct both swollen and pattern not seen in other very robust. Habropoda. In females, hair on T5 is longer, denser, and slightly redder, while in males this is true of T7. In males, the apex of the pygidial plate appears shallowly bilobed. SIMILAR SPECIES: The patterning on the abdomen is unique to this bee, and not seen in any other species of Habropoda.

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— Habropoda morrisoni SIZE: Medium

to large; 13–15 mm. through May. FLORAL HOSTS: Unknown but may specialize on Cryptantha (cat’s eyes). RANGE: Found throughout the western U.S., but absent from Canada, and absent from hot deserts. East side of the Sierra Nevada to South Dakota; Washington to southern Utah. NESTING: Ground-nesting. IDENTIFICATION: Large bee with contrasting colors on the thorax and abdomen. HEAD: Coated in dense blonde to rusty-red hair. In females, the clypeus is entirely black; in fact there are no yellow markings anywhere on the face. In males, clypeus, supraclypeal area, and paraocular area are white. On the clypeus there are two black dots near the anterior tentorial pits. The mandibles and labrum (which is large) are Scutum and first tergal entirely black. Also segment of abdomen are in males, the scape, the same straw color. facing away from face, is white. THORAX: Covered in thick short blonde to rusty-red hair that fades to black underneath. Scutum is covered in pits, though these are hard to see through the hair. Tegulae are brown to orange. LEGS: Hair on PHENOLOGY: March

Habropoda morrisoni (female)

Integument is rough, matte black.

Scopal hairs are dark and coarse.

Habropoda morrisoni (male) Clypeus, supraclypeal, and paraocular area are white; mandibles and labrum are black.

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legs is all black. In females, this includes the coarse scopal hairs. ABDOMEN: The first tergal segment is covered in thick hair the same color as that on the thorax. Subsequent tergal segments have a matte-black integument clearly visible through very sparse black hairs. In males, T7 has almost silvery woolly hairs around the pygidial plate. SIMILAR SPECIES: Similar in size and overall vestiture to Habropoda cineraria. Females of that species have red-orange scopal hairs, however, which should make them easy to distinguish.

— Habropoda pallida SIZE: Medium

to large; 13–15 mm. through June. FLORAL HOSTS: Generalist, with some preference for Creosote (Larrea tridentata). RANGE: Southern Utah and New Mexico, west to southern California and to the Mexican border. NESTING: Ground nester, usually in sandy slopes. IDENTIFICATION: Uniformly light gray bee with white hair bands on abdomen. HEAD: In both females and males, there are white markings. In females, the clypeus is more than half white, with black around the outside edge, and there is also white above the clypeus, and on the middle of the mandibles. In males, the mandibles (especially basally), the clypeus, and the supraclypeal area are all ivory. In addition, the scape, on the surface facing away from the bee, is ivory colored in males. Also in males, the clypeus has black dots, below each anterior tentorial pit. In both sexes, hair on the head is light gray, with some few black hairs mixed in at the vertex. PHENOLOGY: March

Habropoda pallida (female)

The appressed hairs on the abdomen contrast with the fluffy hairs on the thorax.

Unlike other Habropoda females, this species has yellow on the clypeus.

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290  Apidae THORAX: Covered

Note the black dots on the

Overall, a very

in clypeus, and the yellow on gray bee light gray hair, short the underside of the scape. and dense (may be hard to see in worn specimens). Scutum finely and densely pitted, on a dull integument. The tegulae are reddish. LEGS: In females, Habropoda pallida (male) scopal hairs are clear to whitish. Also in females, hairs on the inner surface of tibia (especially hind tibia) are orange. Finally, the tarsi and tibial spurs are reddish. ABDOMEN: Hairs on T1 erect and gray (as on the thorax), becoming flattened toward the apical margin. Hairs on T2–T4 are entirely flattened, not sticking up at all, short, dense, and white at the apex, thinning at the base; in females, these black-and-white bands may be more distinct, giving a stronger black-and-white-striped appearance. In females, at the apex of T5, hair is white and dense; hair on T6 near the very large pygidial plate is almost gold. SIMILAR SPECIES: Females are completely distinct from any other female Habropoda because of the yellow clypeus; a trait usually restricted to males. In addition, the appressed hair on the abdomen is unique, in both sexes, among Habropoda species.

ANTHOPHORULA — SUBFAMILY: Apinae — TRIBE: Exomalopsini OVERVIEW: Small hairy bees that fly fast and are really noticed only when they stop on a flower for more than a moment. Appear to be generalists on summer- and fallflowering plants. Nest communally, in burrows shared by several females. Each cell is lined with a thin, waterproof substance. Interestingly, females shape their pollen masses into pedestals on which they lay their eggs, so that the egg and most of the pollen are up off the ground very slightly, presumably minimizing contact with the moist earth and minimizing the chances of mold. IN THE WORLD: There are around 60 species of Anthophorula, in three subgenera. Nearly all occur in Mexico and the U.S., with only two species restricted to South America. In the western U.S. there are more than 40 species. CLEPTOPARASITES: Brachynomada, Nomada, Paranomada, and Triopasites. IDENTIFICATION: Small robust bees, often with striking hair bands on the abdomen and thick scopal hairs (in females). HEAD: The clypeus is flat, black in females, but with some yellow or ivory in males. There is a long row of well-separated hairs lining the inner margin of each compound eye. THORAX: Round, often lacking hairs centrally. WINGS: In North American species, the stigma is small, typically not even half as long as the marginal cell where it rides on the wing margin. May have two or three submarginal cells. LEGS: In females, scopal hairs are dense, branched, and long on the hind tibia

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and hind basitarsus. ABDOMEN: Black, with thick hair, and often with striking hair bands; abdomen red in a few species. SIMILAR GENERA: This genus is most similar to Exomalopsis, of which it used to be a part. See that genus for distinguishing features between this bee and others that look like it.

— Anthophorula compactula SIZE: Small; 6–7 mm. PHENOLOGY: June through September. FLORAL HOSTS: Generalist. RANGE: Nevada and southern Utah east to Texas. Largely absent from the Colorado Plateau. NESTING: Ground-nesting bee. IDENTIFICATION: Small, but distinctive bee seen in desert regions in summer months. HEAD: Ocelli are large, and close together, rising notably above the vertex, which is flat. In females, clypeus is black, but the antennae are light tan. In males, clypeus is yellow, as Anthophorula are the areas next to the compound compactula (female) eyes, the base of the mandibles, and the front (anterior) sides of the scapes, and around the pedicel. The flagellar segments are light tan, marked with strong black bands that delineate each flagellar segment from the next. Striking light green or blue eyes when alive. THORAX: Scutum densely and evenly pitted over whole surface. Covered in thick short hairs. Tegulae are light to dark brown. WINGS: There are two submarginal cells. LEGS: In females, scopal hairs are white, occurring mainly on the hind tibia and hind basitarsus. Hairs on the hind femur are black. In males, the mid and hind basitarsus are covered in black hair on the outer surface, while the tibia has long white hairs. In both sexes, the inner surface of the hind basitarsus has reddish hairs. ABDOMEN: Black integument, but covered with thick dense hairs, with some long pale hairs over the top. On T1, there is a strong carina where the anterior surface folds over to the dorsal surface; the center of the anterior face is folded in, creating a

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Anthophorula compactula (male)

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distinct median depression. Overall, T1 has thick white hair that runs across the whole surface, underneath which there are dense close punctures. The second through fourth tergal segments have thick dense hairs on the apical half of each segment, with longer white hairs over the top. The fifth tergal segment has pale hairs running across the apex. SIMILAR SPECIES: This species, especially the male, is remarkable and easy to recognize. The matted hair on the abdomen, light eyes, yellow-and-black antennae, two submarginal cells, and dense punctation throughout are not seen in other species of Anthophorula.

EXOMALOPSIS — SUBFAMILY: Apinae — TRIBE: Exomalopsini OVERVIEW: Small but robust and hairy bees, often with a polished thorax. Seen most commonly in the height of summer and into fall. Most species are generalists. Nest in the ground, in cracks in dried soil, in dirt roads of sand or clay, often communally with numbers (even hundreds) of females sharing the same nest entrance. There may be evidence of a few species where females provision the nest cells of other bees that nest with them, meaning that they may be semisocial. IN THE WORLD: More than 90 species occur worldwide, all in the Americas and concentrated mostly in the Neotropics. Ten species occur north of the Mexican border, and all are found in western states and provinces. CLEPTOPARASITES: Brachynomada, Nomada, Paranomada, and Triopasites. IDENTIFICATION: Small robust bees, often with a shiny thorax and thick scopal hairs (in females). May have red abdomens. HEAD: The clypeus is flat, black in females and males. There is a long row of well-separated hairs lining the inner margin of each compound eye. THORAX: Often polished, and relatively bald. WINGS: The stigma is large, especially for the small wing. The marginal cell is elongated, extending close to the apex of the wing, but not narrow, and ending abruptly where it bends away from the wing margin. The second submarginal cell is smaller than the first or the third, which are about the same length. LEGS: In females, scopal hairs are dense, branched, and long on the hind tibia and hind basitarsus. Also in females, the basitibial plate is large, and the central area is covered with velvety hairs. ABDOMEN: May be black, with thick hair, or red. Also in females, the transition from the anterior face of T1 to the dorsal face of T1 is marked by a carina that runs the width of the segment. SIMILAR GENERA: Exomalopsis and Anthophorula were once part of the same genus and appear similar to each other. They can be distinguished by the velvety hairs on the basitibial plate, which are usually absent in Anthophorula. In North American males, Anthophorula has a yellow clypeus and labrum. The stigma in Anthophorula is often smaller than in Exomalopsis. It may also appear similar to small Emphorini species (Diadasia, Ancyloscelis). The clypeus in Emphorini is much more protuberant, and the vertex is even more convex than in Exomalopsis. Small Anthophora species (e.g., subgenus Heliophila) may also appear similar. In those species, the stigma is very small.

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— Exomalopsis solani SIZE: Small; 8–9 mm. PHENOLOGY: June through September. FLORAL HOSTS: Generalist. RANGE: Arizona east to West Texas, north to Colorado and Wyoming. NESTING: Ground nester, often utilizing cracks in dry earth as the beginning of the nest. Nests are communal, with a dozen to perhaps up to several hundred individuals sharing one nest entrance. There is also evidence that females with undeveloped ovaries may aid in pollen collection for females with developed ovaries, Exomalopsis solani indicating that these bees may be semisocial. (female) IDENTIFICATION: Small bee with dark Smooth, polished polished scutum, usually visible through scutum gray hair. HEAD: The vertex of the head is very gently rounded, so that the eyes don’t appear to protrude above the top of the head. At the apex of the clypeus (the lower edge) the punctation is sparse, almost absent, Very few pits on T1 and T2 Exomalopsis solani (female) Exomalopsis solani (male)

Hair on outer surface of hind basitarsus is white. On the inner surface, it is brown to light yellow.

This bee nests communally, with multiple individuals sharing the same nest entrance. A related species (E. auropilosa) was found to have more than 800 individuals using the same nest entrance, and the nest was more than 15 feet deep!

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especially compared with its base. In males, the clypeus is dark, with no yellow markings THORAX: The tegulae are light yellow to orange, and see-through. In females, the pits on the side of the thorax near the posterior end are about the same density (or very slightly less) than at the front of this structure (the mesepisternum). The scutum is very smooth and shining, with very few pits. In males, the propodeum has dense pits that cover the dorsal surface. WINGS: The stigma is a little shorter than the length of the marginal cell (about two-thirds as long). LEGS: In females, the hair on the legs is white or off-white, while on the hind basitarsus, the hair on the outer surface is light, while that of the inner surface is light brown to white, never dark brown or black. Scopal hairs are dense, light colored, and fluffy. In males, hairs on the legs are all light, with no dark brown or black hairs intermixed. ABDOMEN: In females, there are few pits on T1 and T2, which are extraordinarily polished. Thin white hair bands run across the apex of each tergal segment, thinning near the middle. In males, tergal segments have a few long light-colored hairs, but no hair bands. SIMILAR SPECIES: Most Exomalopsis are not as polished on the scutum as E. solani; the polish is a character that defines its subgenus (Stilbomalopsis) of four common species. Among the four, two have dark hair on the inner surface of the hind basitarsus, rather than the lighter coloring seen in E. solani. Exomalopsis solidaginis females are almost impossible to distinguish from E. solani. In E. solidaginis, the pits on the side of the thorax are denser at the front (anterior) end than at the posterior end. In males, those two species differ according to the punctation on the dorsal surface of the propodeum. In E. solidaginis, there are not pits or hairs on the propodeum, as there are in E. solani.

CENTRIS — SUBFAMILY: Apinae — TRIBE: Centridini OVERVIEW: Medium to large, fast-moving bee, some species with bright red eyes and extremely brushy pollen-collecting hairs on the hind legs of females. Most species are specialists, though a few generalists occur. Many species collect floral oil, in addition to pollen, from flowers. Ground-nesting species that often occur in aggregations of a dozen to several thousand. IN THE WORLD: Around 225 species around the world, in North and South America, mostly hotter and more tropical regions. Twenty-two species occur in the U.S. and Canada, with 20 species in the West. CLEPTOPARASITES: Ericrocis. IDENTIFYING FEATURES: Large bees with robust scopal hairs. HEAD: The first flagellar segment of the antenna is longer than the scape. In many species, the eyes appear bright red or green while the bee is alive. WINGS: The outside edges are covered in short stiff hairs. The stigma is relatively small. The first submarginal cell is smaller than the second (there are three). LEGS: There is no arolium. The scopal hairs cover both the hind tibia and the basitarsus and are exceptionally thick and stiff. In many

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species, on the fore- and midlegs, there are large combs of flattened bristles near the tibial spurs, likely used in collecting oils from flowers. SIMILAR GENERA: Few genera in the U.S. look similar to Centris. The large scopae, fast flight, and eye color are three features that make this bee unique. From a distance, Centris may appear similar to Anthophora. The density of the scopal hairs should separate the two. In addition, the first submarginal cell is bigger than the second submarginal cell in Anthophora.

— Centris cockerelli SIZE: Medium; 13–14 mm. PHENOLOGY: April through June. FLORAL HOSTS: Likely a specialist on Fabaceae, including Cercidium, Acacia, and Parkinsonia. RANGE: Deserts of the Southwest. New Mexico west to southern California, north to Colorado and Nevada. NESTING: Ground-nesting bee, often in aggregations. Males, which emerge before females, may be observed patrolling areas where females might emerge, and may dig down to meet the female as she is emerging. IDENTIFICATION: Large, fuzzy, fast-flying bee. HEAD: The area next to the compound eye (the paraocular area), the mandibles, and the labrum have some light coloring; may be just a small patch, or may be extensive. In females, the first flagellar segment is about the same length as the second and third. In females, the clypeus is light yellowish or even reddish, polished; there may be some dark areas, but it is less than half of the whole clypeus that is dark. Also in females, the mandible has four teeth. In most individuals, there is no red line behind the compound

Some light hair on T1

The femurs are dark red to black. No red line near the compound eye (compare to Centris rhodopus)

Thick black scopal hairs

Centris cockerelli (female)

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eye near the top. In males, the Centris cockerelli mandible may be all yellow or (male) all dark. Also in males, the antennae are all black, or may have some limited yellow; the first flagellar segment is shorter than the second and third combined. THORAX: Coated in dense light blonde hair. LEGS: In females, the scopal hairs are all black. The femurs are brownish red to black. In males, the hair on the hind femur is all dark. ABDOMEN: In females, the hair on T1 is usually all light but may contain some dark hair mixed in on the Even males have thick hairs anterior surface, while on T5, the hair is all dark. On on hind legs. S2–S4, the hairs that line the rim of each segment are all dark. In males, on T2, the hair is all dark. There are no clear, distinctive hair bands. SIMILAR SPECIES: Appears similar to Centris rhodopus with blonde hair on thorax and dark hair on abdomen. Female C. cockerelli are smaller than C. rhodopus, and they lack the red line near the compound eye. The color of the femur in females also tends to be more of a brick red in C. cockerelli, but more bright red in C. rhodopus.

— Centris pallida SIZE: Medium

to large; 13–16 mm. through early June. FLORAL HOSTS: Likely a specialist on Fabaceae, including Cercidium, Acacia, and Parkinsonia. RANGE: Deserts of the Southwest. New Mexico west to southern California, north to Colorado and Nevada. NESTING: Ground nester, sometimes in aggregations. IDENTIFICATION: Hard-to-miss desert bee, often with green eyes. HEAD: The area next to the compound eye, beside the clypeus (the paraocular area), the mandibles, and the labrum are all dark. In females, the first flagellar segment is longer than any of the next four. The clypeus is entirely dark, not shiny, with just a few light (never reddish) markings. If there are any, they are usually on the lower half. Also in females, the mandible has three teeth. In males, the mandible may be all yellow, or it may have the apical third dark. Also in males, the antennae are all black. THORAX: Hair on the thorax is light all over, especially on the sides of the body. LEGS: In females, scopal hairs are mostly black, but with a thin light patch that runs from the basitibial plate down the tibia. In males, the hair on the hind femur is all light, or a mix of light and dark. PHENOLOGY: April

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Centris  297 ABDOMEN: In females, on T1 and T2 the hair is all light, and on T5, there are light and dark hairs intermixed. In males, T5 is all light hairs, or a mix of light and dark hairs. On S2–S4 the hairs that line the rims of each segment are all light. In males, T2 has all light hair, while T5 is all dark hairs. Also in males, there are dense appressed light hairs at the Centris do not have an arolium. apex of T1–T4. SIMILAR SPECIES: Few Hair on the top of the Centris species and sides of thorax are entirely blonde on the is all light. thorax; most have some black hairs intermixed. Of those that are all light colored, female C. pallida usually have a dull black clypeus, three teeth in the mandible, and black scopal hairs.

Centris pallida (male)

T1 and T2 are covered in light hair. Light hair and dark hair are on T5.

The clypeus is dull and black. The eyes on this bee, when alive, are yellow/green.

Centris pallida (female)

Scopal hairs mostly black, with a light patch of hair near the base of the tibia

Clypeus dull black

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— Centris rhodopus SIZE: Large; 15–16 mm. PHENOLOGY: April through July. FLORAL HOSTS: Appears to have preferences for Larrea tridentata and plants in the Fabaceae. RANGE: Pacific Coast east to Texas, north to Idaho, Utah, Nevada, and Colorado. NESTING: Ground nester, sometimes in aggregations. IDENTIFICATION: Loud, fuzzy, fast-flying bee, often with bright red eyes when alive. HEAD: The area next to the compound eye (paraocular area), the mandibles, and the labrum have extensive yellow marking extending up past the top of the clypeus. The clypeus is polished, but pitted, with pits generally widely spaced. In Centris rhodopus females, the first flagellar (male) segment is about the same length as the second and third. In females, the clypeus is light yellowish or even reddish; if there are dark areas, they represent less than half the whole surface. In females, the mandible has four teeth. Behind the compound eye, near the top of the head, there is a line of red coloring. In males, the mandible may be all yellow, or may have the apical third dark. Also in males, the antennae are all yellow, especially the scape.

There are light hairs on the hind femur.

Centris rhodopus (female)

This Centris species looks similar to C. cockerelli, but the femur is much brighter red.

There is a little white hair on both T1 and T2.

Thin red line next to the compound eye (compare to Centris cockerelli)

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e 2.

Apis  299 THORAX: Coated in thick light blonde hair. LEGS: In females, the scopal hairs are all black. The femurs are bright red. In males, the hair on the hind femur is all light, or a mix of light and dark. ABDOMEN: On T1, the hairs on the dorsal surface (facing up), are a mix of light and dark hair, with more yellow hair near the base where it folds over to the anterior face, and more black hair along the apical rim. On T2 there is a mix of light and dark hair. In females, the pygidial plate is concave at its apex. On T5, the hair is all dark. On S2–S4, the hairs that line the rim of each segment are all dark. In males, T2 has a mix of dark and light hairs, and T5 is all dark hairs. Also in males, hairs at the apex of each tergal segment are white, with darker hairs more at the base. SIMILAR SPECIES: Appears similar to C. cockerelli. See that species for distinguishing characteristics.

APIS — SUBFAMILY: Apinae — TRIBE: Apini OVERVIEW: Medium-sized, amber-colored bees. Though many consider Apis the “quintessential” bee, it is not native to North America and can be invasive. They share few natural history characteristics with other bees found in this region. Apis are highly social species, living in colonies of up to 50,000 individuals. Within a colony, tasks are divided among female workers. Only one individual, the queen, actively produces offspring; she makes one mating flight, when she mates with multiple males. This one mating flight is enough for her to lay fertilized eggs for the next five to seven years. In just one day, a queen may lay 1,000–2,000 eggs. She and her developing offspring are fed by workers. Depending on what these offspring are fed, they will develop into future queens or additional workers. Because colonies are perennial, these bees are generalists, but an individual bee may collect nectar or pollen from one kind of flower on a given trip. IN THE WORLD: Seven species occur in the world. Most are found in Southeast Asia and India, but also tropical Africa. Two species, Apis mellifera and A. cerana, have been domesticated. Apis mellifera has been moved around the world and is widely used for pollination and honey production. CLEPTOPARASITES: No other bee species are known to parasitize Apis. IDENTIFYING FEATURES: Medium-sized bee with some fine hair on the thorax. HEAD: Compound eyes are hairy. Inner margins of compound eyes converge toward the bottom. Mandibles are simple, with few notable teeth. THORAX: Covered in fine light auburn hair, through which the integument can be seen. WINGS: Marginal cell is extraordinarily long, extending almost to the end of the wing, and is rounded at the end. There are three submarginal cells, which end well back from the wing apex; the second is triangular in shape, rather than cuboidal. LEGS: In females, pollen is collected on a corbicula. As the bee flies, the wet pollen mass may be visible, even if the corbicula is hard to discern. Hind legs often hang below the body. The hind basitarsus is about as

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300  Apidae

wide as long. There are no hind tibial spurs. ABDOMEN: Honey colored with variable striping on the abdomen (some species have white stripes). SIMILAR GENERA: Apis may look similar to Andrena or Colletes because of their size, overall body shape, and similar coloration. The flattened hind legs, hairy compound eyes, and unique wing venation of Apis are distinguishing characteristics.

— Apis mellifera SIZE: Queen: 18–20 mm; worker: 10–15 mm; male: 13–18 mm. PHENOLOGY: Seen from very early in the year all the way through flowering season. FLORAL HOSTS: Very broad generalist. RANGE: Nonnative bee introduced several hundred years ago, with populations originating in many areas throughout the Eastern Hemisphere. It continues to be imported into North America and is now widespread throughout North America, especially in rural areas. NESTING: Nests in hives; most often hives are man-made, but feral colonies can also be found in hollow trees and other large cavities (these more commonly in the southern parts of the U.S.). Apis mellifera coloration ranges from light orange to dark brown.

Marginal cell is very long, extending nearly to the end of the wing.

Compound eyes covered with long hairs

Apis mellifera (female) Hind legs with corbicula (flattened, smooth area on the hind tibia with long hairs that wrap around it)

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IDENTIFICATION: See genus

Apis mellifera (male)

description for features; this is the only species in North America. Most individuals seen are females. In flight, females often hang their legs below the body, rather than holding them up tightly as many other bees do. HEAD: Males (drones) have large eyes that almost touch on top of the head. ABDOMEN: Shiny, may be variably colored from all black to very light colored, but usually with dark bands running across at Apis mellifera scutellata (female) least the first two tergal segments. SIMILAR SPECIES: Apis mellifera is the only species of Apis in North America. For similar genera, see above. There are nearly 24 A. mellifera subspecies that occur throughout the U.S. and Canada. They differ mostly in color patterns and behavior.

Drones have large eyes that almost touch on the top of the head.

Africanized (killer) bees are morphologically indistinguishable from other subspecies.

BOMBUS — SUBFAMILY: Apinae — TRIBE: Bombini OVERVIEW: Large, fuzzy bees, striped with black, yellow, and orange. Conspicuous flower visitors from early spring through the fall. Bumble bees are social bees with annual colonies. While the phenology differs from species to species, with some colonies ending the season much earlier than others, the pattern followed by a colony generally follows the same sequence. Colonies begin anew each year, with queens emerging in the early spring to initiate nesting. They are large bees, often observed in early spring flying slowly over the ground, examining various cavities for potential nesting sites. Chosen sites are often abandoned rodent burrows or hollow areas near grass tussocks; they have also been found in old flowerpots, bird boxes, and other places that provide shelter. The queen’s first generation of daughters are small and develop within two months of the queen’s initial flight. Once mature, these daughters become the primary harvesters of pollen and nectar, and the queen stays in the nest producing more broods. Brood clumps following that first one are often larger, though never as big as a queen; thus, the size of individual bumble bees may grow as the

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season progresses. By mid to late summer, a colony will grow to include between 50 and 300 individuals. At this time, the queen lays eggs that will become male bumble bees, and also eggs that will become next year’s queens. Males leave the nest to find queens from other colonies. All worker bees in a season perish in the fall. Mated queens overwinter in hibernacula and emerge the following spring to start the cycle again. Because the colony is active across multiple seasons, bumble bees are generalists, though they may focus on one plant genus during a foraging flight. IN THE WORLD: Around 260 species occur worldwide, found mostly in the Northern Hemisphere, with a few species in northern Africa, Central America, and South America. They are more common at higher elevations than lower. In North America, there are almost 50 species, with nearly all of them found in western states and provinces of the U.S. and Canada. CLEPTOPARASITES: One subgenus, Bombus (Psithyrus), parasitizes other Bombus species. IDENTIFYING FEATURES: Generally large bee (some workers can be very small) with thick yellow-and-black hair on the head, thorax, and abdomen, where it often appears as stripes. Some species also have white, orange, or red stripes on the abdomen. Under the hair, the integument is completely black. HEAD: In males the clypeus is never colored, but it may have thick, long, colored hairs covering the surface. In females the clypeus is hairless and usually polished. In many species the malar space is often longer than wide, giving the face an elongated look. THORAX: Covered in thick hair, which may be all yellow or a mixture of yellow and black hairs. The location of patches of yellow-and-black hair are important for distinguishing species. WINGS: Usually dark, clear in some species. The jugal lobe is missing from the hind wing in all species. On the forewing the stigma is very short and there are three submarginal cells. LEGS: In females, there is a corbicula on the hind leg. The tibia is flattened, even slightly concave, and hairless, except for a fringe of hair around the outer edges (Bombus [Psithyrus] lack this character). The basitarsus is enlarged and rectangular. Hind tibial spurs are present. The tarsal claws are split. ABDOMEN: Tergal segments are colored in various combinations of yellow, black, red, and white. The combination is often a major factor used in distinguishing species. One subgenus of Bombus, Psithyrus, parasitizes other species in the same genus. There are 29 species of Psithyrus in the world, with six in North America, all of which occur in western states and Canadian provinces. The overall form of this subgenus is similar to other Bombus species, but females lack a well-developed corbicula. Instead, the hind tibia in females is slightly convex, and hairy. Male Psithyrus can be distinguished by the notably smaller heads and the bare patches on T4–T6. While many bumble bee species can be easily identified on the wing, there are also several Bombus species that are difficult to distinguish from each other; their hair patterns are variable, even in the same colony, and there is considerable size and morphological variation between queens, workers, and males. SIMILAR GENERA: The large size of Bombus queens gives them a similar appearance to Xylocopa. The rounder face, the presence of scopal hairs, and the off-white markings on the face of male Xylocopa (not present in any Bombus) should help to distinguish.

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Several other large Apidae are similar in appearance to bumble bees. Some Anthophora species are orange and sized like female worker Bombus. The shorter malar space in Anthophora, scopal hairs (in females), and yellow clypeus (in males) should differentiate the two. Also, the marginal cell in Anthophora is much shorter than in Bombus, and Anthophora have a jugal lobe, which Bombus do not.

— Bombus occidentalis SIZE: Queen: 20 mm; worker: 8–14 mm; male: 12–15 mm. PHENOLOGY: Queens appear as early as March; worker workers can be seen through August. FLORAL HOSTS: Broad generalist. RANGE: Throughout western North America, from the North Slope of Alaska, south along the Rocky Mountains, the queen Sierra Nevada, and the Pacific Coast ranges, to central New Mexico and Arizona. Typically Black hair between the tegulae montane, and largely absent Yellow hair in front from the Great Basin. of the tegula Bombus occidentalis was once one of the most common western bumble bee species. Likely because of diseases transferred from managed commercial bumble bees, it has disappeared from much of its range. There are areas of local abundance, however. NESTING: Ground-nesting species. IDENTIFICATION: Moderate to large bumble bee with short, thick hair; it often has white hair on T4–T5. Patterning on the bee is variable, with two forms common. HEAD: The malar spaces are short (wider than long). In females, hair on the face is usually grayish. Also in females, the upper portion of the clypeus appears swollen

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Black and yellow hair intermixed behind the tegula

Bombus occidentalis (female worker) T1 through T3 are all black.

T4 and T5 are white.

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304  Apidae Bombus occidentalis (female)

The malar spaces are short (wider than long).

Bombus occidentalis (male)

in profile, though this can be hard to see through the hair. THORAX: Between the tegula, the hair is black, usually extending as a stripe, but may be just a central spot. The area anterior to this region is covered in yellow hair, while the area behind may be yellow, black, or a mix. LEGS: In females, the hind basitarsus is curved at its posterior margin. ABDOMEN: In all individuals, T1 is black. And in all queens, T5 is white, which is not seen in other western species. In “typical” worker species, T2 and T3 are also black, with T4–T5 exhibiting bright white hairs that run the width of the segment. In some individuals, however, T2 and T3 are yellow, or yellow and black, and T5 is orange (this morph is more common in the Intermountain West). SIMILAR SPECIES: The eastern and northern species, Bombus terricola, is similar enough that it was thought that B. occidentalis was a subspecies for many years. Genetic evidence shows they are distinct species, though difficult to distinguish. With the exception of north-central Canada, the ranges of the two species do not overlap. Bombus mckayi, a rare species that occurs in Alaska and western Canada, is another that was once a subspecies of B. occidentalis. It has a yellow band between wings, and yellow band on T3; its hair tends to be longer. Similarly, Bombus cryptarum, which occurs in the northern Canadian Rockies and into Alaska, shows a similar color pattern. The punctation on the clypeus is larger in this species, which also tends to be darker. No other bumble bees share the white T4–T5 patterning seen in this species. For those individuals that do not exhibit the “typical” pattern, they may appear similar to B. vosnesenskii and B. vandykei, which are restricted to California and have longer faces. Other bumble bees that look superficially similar have yellow on T1.

— Bombus griseocollis SIZE: Queen: 20–23 mm; worker: 10–18 mm; male: 15–18 mm. PHENOLOGY: Queens appear in May, and workers appear a month later and fly through September. Males can be seen from July through October. New queens appear in August and September. FLORAL HOSTS: Very broad generalist. RANGE: Found throughout North America. Seldom seen in the Southwest except at higher elevations. NESTING: Nests underground or in

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Bombus  305

grass tussocks aboveground. Colonies are small, no more than 50 workers. IDENTIFICATION: Larger bumble bee with short and even pale yellow hair. HEAD: The malar spaces are clearly shorter than broad. Hair on the front of the face is black or sometimes mixed with light yellow. On the vertex, hair is black. In males, the eyes are bulging and converge slightly. THORAX: In both sexes, yellow, often with a black spot on the scutum. ABDOMEN:  The first tergal segment is yellow. The second tergal segment is yellow or orange brown, at least centrally; the apical margin of T2 is usually black hair, as are the apical margins of T3–T5. In males, T1 is yellow, T2 is medially yellow, and T3– T6 are black.

worker

queen Thorax with yellow hair, sometimes with a black spot in the center T1 is yellow, and T2 is yellow or orangish brown centrally. T3–T5 are black.

Bombus griseocollis (female)

SIMILAR SPECIES:

Most similar to Bombus morrisoni, which is generally the more common of the two in the West. Bombus morrisoni has yellow on T3, while B. griseocollis does not. In addition, B. griseocollis is a lighter yellow, while B. morrisoni is a deep yellow.

Bombus griseocollis (male)

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— Bombus morrisoni

worker

SIZE: Queen:

22–26 mm; worker: 12–20 mm; male: 15–20 mm. PHENOLOGY: Queens are usually seen in May; workers and males fly queen through September. FLORAL HOSTS: Broad generalist. RANGE: Dry open areas of the western U.S.; more abundant in southern Rocky Mountains and absent from the northern Plains. New Mexico west to eastern Arizona; north through Idaho. NESTING: Nests in the ground. IDENTIFICATION: Larger bumble bee with even, short, bright yellow hair. Individuals exhibit little variability in appearance. HEAD: The face is short, with the malar The upper surface space much shorter than wide. Hair of the thorax is all yellow. on face may be all black, or a mix of yellow and black. Simple eyes are large, compared with other Bombus. THORAX: On the sides of the thorax, beneath the tegula, the hair is black. The dorsal surface of the thorax is all yellow, with no central black spot or stripe Bombus morrisoni (female)

Malar space much shorter than wide

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Behind the tegula, the area on the side of the thorax is black.

Bumble bees collect pollen in a corbicula, instead of on scopal hairs.

T1–T3 are all yellow. T4 has yellow just at the base. T5 is black.

Bombus morrisoni (female)

In queens, only T1–T3 are yellow.

Bombus morrisoni (queen)

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Bombus  307

(some few black hairs may be present). ABDOMEN: Tergal segments one through three are entirely yellow. The fourth tergal segment may be yellow on the basal edge, while T5 is all black. SIMILAR SPECIES: May appear somewhat similar to B. griseocollis (see that species for distinguishing features). With the extensive yellow hair on the abdomen, it may also appear similar to B. pensylvanicus. That species has Bombus morrisoni black running between the terga. (male)

— Bombus rufocinctus SIZE: Queen: 18 mm; worker: 10–13 mm; male: 11–15 mm. PHENOLOGY: April through October, with workers and males June through September. FLORAL HOSTS: Broad generalist. RANGE: Southern Canada and northern U.S., south down mountain chains of the western U.S. to central California, Arizona, and New Mexico. NESTING: Nests at This individual has ground surface, black on T3 and T4, and occasionally instead of orange. above ground in cavities.

worker

queen

Bombus rufocinctus (female)

IDENTIFICATION:

Smaller bumble bee with short even hair, round head, short tongue, and ample red on abdomen, though the patterning on the abdomen is highly variable in this species. HEAD: In females, on the face, a mix of yellow-and-black hairs occurs, but the vertex is yellow. On the mouthparts, the tongue (glossa) is very short. Malar space is short,

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The thorax is all yellow, but there is a black stripe between the tegulae.

The hair patterns on this bee are variable. Here, T1 and the anterior half of T2 are yellow. T3 and T4 are orange.

Bombus rufocinctus (female)

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308  Apidae Bombus rufocinctus (female)

Bombus rufocinctus (male)

Malar space is short.

so that face appears round. In males, the vertex may be a mix of yellow-and-black hair. Also in males, the flagellum is exceedingly long, nearly three times the length of the scape. THORAX: In females, hair on thorax is yellow, but between the tegulae is a stripe of black hair. On the sides of the thorax, the hair is yellow. In males, area between the tegulae may be black, or may be a mix of black-andyellow hairs. ABDOMEN: Hair patterns variable, but typically T1 and the anterior portion of T2 are yellow; on T2 the yellow is in a yellow C shape and may be surrounded on the posterior half of T2 with either yellow, black, or red-orange hair. The third and fourth tergal segments are often orange but may be black. SIMILAR SPECIES: Appears somewhat similar to B. melanopygus, B. bifarius, B. huntii, and B. sylvicola. In all cases, the face and the tongue of B. rufocinctus are shorter than in any of these bees. In B. melanopygus, the thorax has a mix of yellow-and-black hairs anterior to stripe between tegulae, which are often more triangular than linear. In B. bifarius, T2 may be black or red, but never has a yellow central area. In B. sylvicola, the hair is very long and shaggy, as opposed to the short even hair of B. rufocinctus.

— Bombus vancouverensis 15–19 mm; worker: worker 8–13 mm; male: 8–13 mm. PHENOLOGY: Queens emerge in late March through June. Workers appear in May but are queen most common in July and August. Males fly in August through September. FLORAL HOSTS: Broad generalist. RANGE: Bombus bifarius historically consisted of what are now considered two species: B. vancouverensis ranges from Alaska and Canada south through northern California and Idaho, while B. bifarius, in the narrow sense, occurs in the Rocky Mountains and Colorado Plateau, north through Wyoming, barely east to Nebraska, and west to Utah. NESTING: Nests in the ground. IDENTIFICATION: Medium-sized bumble bee with moderately long even hair. Can be SIZE: Queen:

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Bombus  309 Mix of black and yellow hair in front of tegula

Strong triangular notch of black hair on scutellum

Bombus bifarius (female)

Bombus bifarius (female)

The malar space is as wide as it is long.

identified by the black notch on the thorax. HEAD: In females, face is almost entirely yellow. The malar space is as wide as it is long, so that the face appears round. On the vertex, the hair is mostly yellow but may have a few black hairs. THORAX: In both Bombus bifarius (male) males and females, scutellum has strong triangular notch of black hairs pushing posteriorly into the yellow, or yellow-and-white, hair that dominates the posterior portion of the scutellum. On the sides of the thorax, the hair is yellow. ABDOMEN: The first tergal segment may be yellow or pale white. On T2 and T3, the hair is mostly red, mostly black, or a mix of the two. The fourth tergal segment is yellow, and T5 and T6 are black. SIMILAR SPECIES: Bombus bifarius appears very similar to B. vancouverensis. Bombus bifarius never has a black form, or any intermediates, while B. vancouverensis tends toward a mix of mostly red on T2 and T3. Bombus bifarius is a common species in the Rocky Mountain region, while B. vancouverensis occurs up and down the West Coast. Bombus bifarius is also similar to Bombus huntii, but that bee does not have the V-shaped notch in the hair patterning on the thorax. Bombus huntii is more likely to have red on the abdomen.

— Bombus centralis SIZE: Queen: 16–18 mm; worker: 10–13 mm; male: 12–14 mm. PHENOLOGY: Late March through September, with workers April through August, and males July through August. FLORAL HOSTS: Broad generalist. RANGE: Widely distributed throughout the western U.S., except for western California; its distribution ends in the Sierra Nevada. Usually seen in meadows or high grass plains. NESTING: Usually nests underground.

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IDENTIFICATION: Medium-sized bumble bee with longer tongue, and some red on abdomen. Remarkably, there is very little variation in the color patterning of worker this species. HEAD: Longer face, with malar space longer than broad. Hair on face and on vertex mostly yellow with very little black mixed in. In males, the first flagellar segment is queen long, about twice as long as it is wide, and the entire flagellum is nearly three times as long as the scape. Also in males, the eyes are not enlarged, as in some other bumble bees. THORAX: Yellow, with a strong black band running between the tegulae. Sides of thorax yellow. In males, black band may have yellow intermixed so that it is less distinctive. The areas behind the tegulae in males is all yellow, with no black hairs. ABDOMEN: Tergal segments 1 and 2 are yellow; but Bombus centralis may have some black hairs centrally. (male) The third and fourth tergal segments are orange, the fifth tergal segment is black. SIMILAR SPECIES: This bee appears very similar to B. flavifrons, and the range

In females, there is yellow hair behind the tegula. Yellow thorax with thick black band between tegulae

T1 and T2 are yellow, but with little hair centrally T3 and T4 are orange.

Bombus centralis (female)

Malar space longer than broad

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Bombus  311

of the two overlaps considerably. They can be distinguished by the broad black hair band on the thorax, which has yellow hairs in B. flavifrons females. In males, the thorax of B. flavifrons has yellow-and-black hairs intermixed posterior to the tegulae, but this is not the case in B. centralis.

— Bombus flavifrons SIZE: Queen: 16–18 mm; worker: 10–13 mm; male: 10–13 mm. worker PHENOLOGY: Queens emerge in May, with workers reaching peak abundance in July and diminishing by September. Males are present from late June through September. FLORAL HOSTS: Broad generalist. queen RANGE: North of the Arctic Circle to the Pacific Coast; east to the Rocky Mountains, south to southern New Mexico. Absent from lower elevations in central California and the Great Basin. NESTING: Nests in the ground. IDENTIFICATION: Medium-sized bumble bee with medium hair with two distinct color forms. In the Pacific coastal states, and northern California, T3 and T4 are black, while in Alaska, south along the Rocky Mountains and associated ranges into Utah, T3 and T4 are red. HEAD: Head is long, with the malar space much longer than it is wide. Hair on vertex yellow, or a mix of yellow and black. In males, eyes are not greatly enlarged; about the Even mix of yellow and black hairs Yellow hair on same size as in females. across thorax T1 and T2

Orange hair Bombus flavifrons on T3 and T4 (female)

Bombus flavifrons individuals from Oregon, Washington, and California have yellow on T1–T3, with black at the center, and no orange.

Bombus flavifrons (female)

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Malar space much longer than it is wide

Bombus flavifrons (female)

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Male antennae are long, with the first flagellar segment about as long as the third. THORAX: In females, thorax an even mix of yellow-and-black hairs. Between the tegulae, more black hair may be present as a central spot. The sides of the thorax are yellow. In males, the front half of the thorax lacks black hair, appearing lemon yellow. Between tegulae, there is usually a stripe of black hair intermixed with yellow. Posterior to this, the hair is Bombus flavifrons yellow laterally, but darker centrally. (male) ABDOMEN: There are two color forms of this species. Bees from Oregon, Washington, and California are as follows: T1–T3 are yellow, especially laterally, but may have black hair at the center of T1 and T2. Bees from other regions have yellow on T1 and T2 but are orange on T3 and T4. The fifth tergal segment is typically black in both forms. In males, some specimens are yellow for T1–T4. SIMILAR SPECIES: Most similar to B. centralis. See that species for ways to distinguish them.

— Bombus huntii SIZE: Queen: 19–20 mm; worker: 11–14 mm; male: 10–13 mm. PHENOLOGY: Queens emerge in worker April; workers fly late April through September. Males are most common in August and September. FLORAL HOSTS: Broad generalist. RANGE: Sierra Crest east to Nebraska and New queen Mexico. Common in the Colorado Plateau. NESTING: Nests underground. IDENTIFICATION: Medium-sized bumble bee with short, thick hair. Patterning is distinctive and does not vary. HEAD: The head is round, with the malar space about as long as it is wide. In both males and females, the hair on the face and vertex is all yellow. In males, the eyes are about the same size as in females. THORAX: The anterior half of the thorax is all yellow, with a thick band of black hair running between the tegulae. The sides of the thorax are also yellow. The posterior half of the thorax is also yellow but may have a small notch of black. ABDOMEN: In both sexes, T1 is yellow, and T2–T3 are orange. The fourth tergal segment is yellow, and T5 is black. SIMILAR SPECIES: Bombus huntii appears similar to B. sylvicola, B. melanopygus, and B. bifarius. It can be distinguished from B. bifarius by the wedge shape of black hairs on the thorax of B. bifarius, which does not occur in B. huntii. B. bifarius also has more

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Thick band of black hair between tegulae that extends as a wedge on to scutellum

Bombus huntii (female)

T1 is yellow.

T3 and T4 are orange. T4 is yellow.

T2–T3 are orange. T5 is black. T4 is yellow.

Bombus huntii (female)

black hairs mixed with yellow on the anterior half of the thorax. Bombus sylvicola is found in high mountain regions of the western U.S. and is less common. It is a smaller bumble bee with longer, shaggier hair than B. huntii. Bombus melanopygus is most abundant in California. The anterior half of the thorax in B. melanopygus comprises a mix of yellow-and-black hairs; in B. huntii, this area is entirely yellow.

Bombus huntii (female)

Malar space about as long as it is wide

Bombus huntii (male)

— Bombus vosnesenskii SIZE: Queen: 18–21 mm; worker: 8–17 mm; male: 10–15 mm. PHENOLOGY: Queens appear in worker March at lower elevations, and May or June at higher elevations. Workers are present from May through August. Males are common in August. FLORAL HOSTS: Broad generalist. RANGE: queen Very abundant in states along the Pacific Coast, north just into British Columbia. Occasionally found in Nevada. NESTING: Nests in the ground. IDENTIFICATION: Slightly larger bumble bee, mostly black, short, even hair. Little variation in appearance. HEAD: Head is round, with malar space about as wide as it is long. The vertex is bright yellow. On the clypeus, punctation on the lower half has both small and large pits. In males, antennae are long, with flagellum about three times as long as the scape. THORAX: The anterior half of the thorax is bright yellow. All

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Anterior half of thorax bright yellow. All the rest of the thorax is black.

T1–T3 are all black.

Malar space about as wide as it is long

Bombus vosnesenskii (female)

areas from the tegulae to the start of T4 is yellow. the abdomen are covered in black hair. Just seen here, In males, some individuals have yellow hair T5 is black. intermixed with the black. The sides of the thorax are covered with black hair. ABDOMEN: The first through third tergal segments are all black. The fourth tergal segment is yellow. The fifth tergal segment is black; in males, T5 is yellow laterally. SIMILAR SPECIES: Most similar to B. caliginosus and B. vandykei. Bombus caliginosus is another Pacific Coast bumble bee with Bombus vosnesenskii a hair pattern very similar to (male) B. vosnesenskii. It is slightly smaller, but otherwise difficult to distinguish. In females, on the clypeus, the lower half has small pits, but no larger ones, in B. caliginosus. In addition, the yellow band on T4 is often narrower, or interrupted in B. caliginosus. Bombus vandykei appears similar at first glance, and it, too, is restricted to coastal states. It can be distinguished by the hair patterns on the abdomen; in B. vandykei, T1–T2 are black, but T3 has some yellow, at least basally. The fourth tergal segment is usually black. See also B. fervidus for distinguishing features in dark forms of that species.

— Bombus fervidus SIZE: Queen: 18–21 mm; worker: 11–16 mm; male: 15–20 mm. PHENOLOGY: Queens appear in April and May. Workers fly from June through August. Males are common in July through September. FLORAL HOSTS: Broad generalist. RANGE: Widespread across North America, absent from the Southeast, and does not extend north as far as other bumble bees do. NESTING: Nests aboveground, in abandoned mouse nests, or grass mounds.

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Bombus  315

IDENTIFICATION: Large bumble bee with even, medium-length hair. More aggressive than most other bumble bee species. worker Comes in two color patterns; western ones are mostly black, while eastern individuals are mostly yellow. Western ones are sometimes considered a queen separate species—B. californicus. HEAD: Head is long, with malar space much longer than broad. In females, the hair on the face is black; in males some short yellow hairs may be intermixed. In males the antennae are very long, with the flagellum more than four times as long as the scape. THORAX: The thorax is yellow on the anterior half. In many individuals there is a thick black band that extends between the tegulae, but some individuals are all yellow, or have a mix of yellow and black hairs here. The posterior half of the thorax is usually yellow but may be black in some darker forms. The sides of the thorax are usually yellow (again, darker forms may have black sides). ABDOMEN: Either T1 through T4 are mostly yellow and T5 is black, or, in darker forms, T1–T3 may be black while T4 is yellow. SIMILAR SPECIES: Darker forms, which are found in the West, resemble B. vosnesenskii, B. caliginosus, and B. vandykei. Bombus fervidus has a longer face than any of those species. In males, the antennae are much longer in B. fervidus. Bombus fervidus (female)

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Bombus fervidus (male) Hair on the head black

Black stripe extends across middle of thorax.

Variable species; usually, T1–T4 are yellow and T5 is black.

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Bombus fervidus (female)

— Bombus pensylvanicus SIZE: Queen: 22–26 mm; worker worker: 13–19 mm; male: 13–16 mm. PHENOLOGY: Queens appear in May and June. Workers fly from July through August. Males are common in queen September. FLORAL HOSTS: Broad generalist. RANGE: Widespread in the eastern and midwestern U.S. and across the southwestern U.S.; rarely up the coast to Oregon. Rare in southern Canada. This species has two subspecies that have been called separate species in the past. Bombus pensylvanicus pensylvanicus is widely distributed throughout the East and is a darker form of the bee; this subspecies appears to be declining in some areas. Bombus pensylvanicus sonorus is found in California and the Southwest; distinguishing characteristics are discussed below. NESTING: Nests aboveground, Anterior of thorax is yellow in all forms. in abandoned mouse nests or grass mounds. Bombus pensylvanicus

IDENTIFICATION:

T1–T3 lemon yellow (T1 may be black in individuals from Midwest)

(female)

Large bumble bee; mostly yellow with short, even hair. More aggressive than most other bumble bee

T4 and T5 black

The face is very long; the malar space is longer than it is wide.

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The posterior portion is black in some subspecies, but yellow in specimens from California and the Southwest.

Black stripe across center of thorax

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species. HEAD: The face is very long; the malar space is longer than it is wide. The antennae are very long In females, the vertex and the face are in males of this species. covered in black hair, with no yellow mixed in. In males the face is mostly black, with some short yellow hairs intermixed. Also in males, the antennae are very long; the flagellum is more than four times as long as the scape. THORAX: Anterior portion is yellow, Bombus pensylvanicus (male) with a black stripe between the tegulae. Posterior portion is black in eastern individuals; those from California and the Southwest have yellow hairs covering the scutellum. The sides of the thorax, below the wings, are black. ABDOMEN: The first tergal segment is usually yellow in western specimens, but may be black, especially centrally; T2 and T3 are yellow all the way across, and T4 and T5 are black. In males, the very tip of the abdomen may be orange. SIMILAR SPECIES: Appears similar to eastern forms of B. fervidus. In the West, appears most similar to B. morrisoni and B. nevadensis. Bombus nevadensis has a slightly longer face, and the black patch between the tegulae is usually a spot, instead of a stripe. If it is a stripe, then the stripe is a mix of black and yellow hairs. With B. morrisoni, the malar space is much shorter than it is wide, as opposed to the long malar space in B. pensylvanicus.

NOMADA — SUBFAMILY: Nomadinae — TRIBE: Nomadini OVERVIEW: Striking red or red-and-yellow parasitic bees seen in abundance in the spring and early summer. Most are nest parasites of Andrena species and are frequently seen hovering just above the ground, looking for nest entrances. With no need to collect pollen, this group has no floral preferences. Occasionally seen in the evening or early morning “sleeping,” with bodies taut, legs tucked up, grasping a plant stem with their mandibles. IN THE WORLD: Nomada is a species-rich genus, with more than 700 species found around the world. Though found on every continent, they are rare in the tropics of South America and Sub-Saharan Africa. There are nearly 300 species in North America, with more than 60 in the East. HOSTS: In North America, mostly bees in the genus Andrena, but also Agapostemon, Halictus, Lasioglossum, Melitta, Exomalopsis, and Colletes. IDENTIFYING FEATURES: Nearly hairless red-and-yellow bee, narrow bodied and wasplike. They range in size from petite to larger than a honey bee. HEAD: The base of the

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mandible is wider than the eye. THORAX: The scutum is overly rounded, rather than flat. WINGS: The marginal cell is very pointed and ends right on the wing margin. There are either two or three submarginal cells (usually three); the width of the first submarginal cell is equal to the widths of the second and third submarginal cells together. ABDOMEN: In females, S5 has a tuft of bristles to either side of center. T6, which is barely visible, has a tuft of hair to either side of the pygidial plate. Nomada are notoriously difficult to identify to species. While some subgenera are distinct, there are many species that have defied being placed in a subgenus with any certainty. For a handful of species, only one sex has been described. Furthermore, there is significant variation in the color patterns of individuals within one species. Below, we have pulled out just two species that can be more easily identified. There is currently no good key to western Nomada. Distinguishing males and females is more difficult than other bees because they lack scopal hairs. Counting antennal segments must be done with caution, because in many males the pedicel is nestled inside the apex of the scape and can be missed (resulting in a count of 12 antennal segments when there are 13). Make sure also to count tergal segments, as females have six exposed, while males have seven. SIMILAR GENERA: No other bee genus exhibits the striking red-and-yellow markings seen on the body of Nomada. They are more likely to be mistaken for wasps than for other bee genera. Brachynomada (not included in this book), which are very rare, may appear similar but lack any yellow markings, and they are entirely black or black and red. The mandibles of Brachynomada are about the same width as the compound eye.

— Nomada edwardsii SIZE: Medium;

10–11 mm. through May. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: California east to Colorado, some few records as far north as southern British Columbia. South to Arizona. Uncommon in the Great Basin. NESTING: Ground nester, in nests most likely built by Andrena and Halictus females. IDENTIFICATION: Larger yellow-and-black cleptoparasite. HEAD: The clypeus is yellow, as is the area between the clypeus and the inner margin of the compound eye, extending up past the antennal sockets (slightly lower in males). In females, the gena is yellow, and there is one yellow spot below the lowest ocelli. Mandibles are simple with rounded teeth, and yellow at the base, but fading to black. Antennae are light brown, to yellow on the underside. In males, the head is hairy, and the gena is mostly black, with yellow just on the lower half. Also in males, the antennae are yellow on the side that faces out from the body, but black on the side facing the head. THORAX: In females, the scutum is predominantly black, with yellow at the sides. The pronotal collar is yellow. The scutum PHENOLOGY: March

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Nomada  319 Nomada edwardsii (female)

Tegulae are yellow.

Black scutum, heavily pitted

Smoky is heavily pitted, and wings incredibly roughened. Tegulae are yellow. Scutellum is swollen, yellow sometimes with a black line at Scutellum its posterior margin. Axillae are yellow, small yellow, slightly and rounded. Metanotum is yellow. Propodeum swollen, often with a black line is yellow with a black propodeal triangle, and at posterior Anterior face margin slopes so dramatically that it appears to face up, of T1 black rather than back toward the thorax. In males, the scutum lacks yellow on the sides, though the scutellum, tegula, and pronotal collar are still yellow. Also in males, there are some sparse hairs on the sides of the thorax. WINGS: Slightly smoky. LEGS: Yellow on the outside, but the interior face (toward the bee) is black. In females there are no scopal hairs. Nomada edwardsii (male) ABDOMEN: Predominantly yellow, with a rough integument but few pits. In females, the anterior face of T1 is black. A thin black line runs across the apex of T2 and T3. On T4, the apex is translucent, and the black stripe on the base of the segment below shows through. In males, the pattern is similar, though the black bands are thicker on T1–T4. SIMILAR SPECIES: There are several Nomada species in the West with this general appearance; because published descriptions and keys for Nomada do not exist yet, specimens should be compared with reference collections for verification.

— Nomada hemphilli SIZE: Small to medium; 9–11 mm. PHENOLOGY: April through June. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: California east to Colorado, south to Arizona, north to Idaho. NESTING: Ground nester, in nests most likely built by Andrena and Halictus females. IDENTIFICATION: Medium-sized mostly red wasplike bee. HEAD: Antennae are red. The frons is black, but all areas surrounding the compound eyes (gena, clypeus, paraocular area, and, in fact, most of the mandible) are red. In males, there is a red spot below the lowest ocelli. Mandible is simple and rounded. THORAX: Sparse hairs and heavily pitted surface, with pits so close together that they appear to push up on each other.

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The tegulae are orange. The scutum is equal parts red and black, with red outlining the dorsal surface and two red stripes running longitudinally the length of the scutum, just off center. The axilla, and the scutum, which is slightly swollen, are red. The metanotum is black. The propodeum is black but the sides each have a red spot, and it faces the abdomen, rather than being so slanted as to face up. In males, patterning is similar to females, but with slightly more red. WINGS: Slightly smoky. LEGS: All red. The apex of the mid and hind femur flares out. In females, no scopal hairs. ABDOMEN: All red. The integument is roughened with shallow pits that extend all the way to the apical rim of each segment. In males, there are darker red-brown stripes on the apex of T1–T3. SIMILAR SPECIES: There are several Nomada species in the West with this general appearance; because published descriptions and keys for Nomada do not exist yet, specimens should be compared with reference collections for verification.

Nomada hemphilli (male)

Nomada hemphilli (female)

Like all cleptoparasites, there are no scopal hairs in females.

TOWNSENDIELLA — SUBFAMILY: Nomadinae — TRIBE: Townsendiellini OVERVIEW: Petite red-and-yellow bees seen rarely in the Southwest. Cleptoparasites of Hesperapis. With no need to collect pollen, this group has no floral preferences. With their diminutive size and cleptoparasitic habit, it is rare to see these bees.

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IN THE WORLD: There are four species of Townsendiella in the world; all are found in the southwestern U.S. HOSTS: Hesperapis. IDENTIFYING FEATURES: Small parasitic bee with short appressed pale hairs. THORAX: With appressed hairs, especially laterally. Lines of hair may run from the anterior margin of the scutum back. WINGS: Two submarginal cells, the first longer than the second. Relatively long marginal cell, longer than the stigma. ABDOMEN: In both sexes, the pygidial plate is clearly evident. SIMILAR GENERA: Few bees appear similar to Townsendiella. Neolarra come closest in size and general body shape. However, the marginal cell is much longer in Townsendiella, exceeding the stigma in length, and the second submarginal cell in Townsendiella is not as reduced as it is in Neolarra.

— Townsendiella ensifera SIZE: Petite; 3–4 mm. PHENOLOGY: Early May to late August. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: Currently known only from Pinnacles National Park, in California. NESTING: Ground nester, presumably in Hesperapis nests. IDENTIFICATION: Tiny bee covered with dense white hair. HEAD: Though difficult to see, the maxillary palp has five palpomeres. THORAX: Metanotum smooth, with no projections along the dorsal margin. WINGS: Marginal cell Second long, the same length as distance from tip of marginal cell to submarginal cell wing tip. Second submarginal cell distinctly curved along its not reduced inner margin (toward wing base). ABDOMEN: Apical hair bands interrupted or reduced at the center. In females, pygidial plate is flat and smooth, with punctures distinct. SIMILAR SPECIES: Townsendiella species are fairly easy to distinguish. This species has no knob at the end of the metanotum, and the marginal cell is elongated. It is most similar to T. pulchra, but the number of palpomeres and the elongated shape of the last one are unique. Also, in males, Townsendiella ensifera the pygidial plate is (female) narrower and Marginal cell relatively long pointier at the tip in T. ensifera compared with T. pulchra. Townsendiella ensifera (male)

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EPEOLUS — SUBFAMILY: Nomadinae — TRIBE: Epeolini OVERVIEW: Epeolus are boldly marked black-and-white chunky bees. They are small to medium in size, and not often seen. The hair is white, appressed, and scalelike on a matte-black body. As cleptoparasites of Colletes, their emergence coincides with that bee; most are seen in mid-spring, but some species emerge in the fall with fall Colletes. They have no floral preferences and can be seen nectaring on a wide array of flowering plants. IN THE WORLD: There are more than 100 species of Epeolus around the world, widely distributed on all continents except Australia. Around 32 species can be found in North America, and around 20 of these occur in the western states and provinces. HOSTS: Colletes. IDENTIFYING FEATURES: Modest-sized black-and-white or red/black-and-white bee with appressed lines and patches of hair on the head, thorax, and abdomen. Not fuzzy at all. HEAD: Though difficult to see, Epeolus are characterized by the maxillary palpus being three-segmented (occasionally two). THORAX: The scutum appears arched instead of flat, as in most bees. The axillae are drawn into long points that hang over the scutellum. Usually with two lines of appressed hairs, starting at the anterior edge of the scutum and extending halfway back. WINGS: The marginal cell is rounded at the tip, ending just off the wing margin. There are three submarginal cells. LEGS: Arolia are present. ABDOMEN: Appressed hairs create white lines running across each tergal segment. In females, on T6 the pygidial plate is wide and short. Just anterior to the pygidial plate is a pseudopygidial area, usually covered with a patch of differently colored, silvery, appressed hairs. The hairs on the edges of S6 in females are cone-shaped. SIMILAR GENERA: Triepeolus can look very similar to Epeolus, and distinguishing the two without close inspection may not be possible. Overall, Epeolus are smaller than Triepeolus. Small male species of Triepeolus may be distinguished from Epeolus only by looking at characters on the genitalia. For females, the pygidial plate is key: in Epeolus it is wider than it is long, with a pseudopygidial area that is shaped like a half-moon. In Triepeolus the pygidial plate is longer than it is wide, with the pseudopygidial area equally elongated.

— Epeolus compactus SIZE: Small; 7–9 mm. PHENOLOGY: Most common from April through July; a few individuals fly in the fall. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: Widespread and relatively common; central Canada (Saskatchewan), south through central Mexico (Durango). California east to Iowa. NESTING: Cleptoparasite of Colletes, which nest in the ground. IDENTIFICATION: Striking black-and-white bee. HEAD: The mandible is rusty red. The antennae are dark, though the first flagellar segment is rusty red. THORAX: The side of the thorax, below the wings, has dense punctures at the top half (ventrally), but sparser punctation toward the lower half. At the center of the scutum, there are two patches of white hair that converge to form a V shape. The axillae are small, extending only half the

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Epeolus  323 T1 is white, but with a rectangular black patch at the center (other species have triangular or oval patterns instead).

The axilla are very small.

Epeolus compactus (female) Legs are mostly red.

Two patches of white hair on the scutum, sometimes V-shaped

distance of the scutellum, and mostly black. The scutellum is also black. The metanotum is entirely covered with short white hairs. LEGS: The legs are partly red, especially toward the lower leg segments. ABDOMEN:  The first White bands run across T2–T4; they are not Epeolus compactus tergal segment is covered in white, interrupted in the (male) center. flattened hair except for a rectangular patch at the center, where the anterior face rolls up to the dorsal face. In addition, at the apical margin of T1, there is a hairless patch at the center. Tergal segments two through four have broad hair bands that continue entirely across the apex of the segment; if they are interrupted at the center, it is only slightly. SIMILAR SPECIES: This species is most similar to E. canadensis and E. ferrarii. These are the species of Epeolus that have a V-shaped patch of white hair on the scutum. Between E. canadensis and E. compactus, the square black patch on T1 is distinctive: in E. canadensis it is semicircular or triangular, instead of square. With E. ferrarii, T2–T4 have white hair bands that are entirely interrupted at the center.

— Epeolus mesillae SIZE: Small; 6–7 mm. PHENOLOGY: March through May. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: Most common in the hot deserts of the southwestern U.S., occurring as far north as west-central Nevada and central Colorado. Does not occur east of West Texas. NESTING: Cleptoparasite of Colletes, which nest in the ground. IDENTIFICATION: Smaller black-and-white Epeolus. HEAD: The mandible is orange, with a brown base. The first flagellar segment is orange. THORAX: The axillae are small, not

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324  Apidae

This species has only two submarginal cells, instead of three! Epeolus mesillae (male)

past the middle of the scutellum. Both the axillae and the scutellum are black. WINGS: There are two submarginal cells. LEGS: Legs are a mix of rust red and dark brown. ABDOMEN: Tergal segments 1–4 all have complete white hair bands running across them, not interrupted at the center. Epeolus mesillae SIMILAR SPECIES: There are only two other (female) Epeolus that have two submarginal cells instead of three: E. americanus and E. asperatus. In both species, however, T1 and T2 are narrowed, or completely interrupted at the center.

The hair on T1 is not interrupted at the center.

— Epeolus minimus SIZE: Small; 7–8 mm. PHENOLOGY: May through July; a few individuals fly in the fall. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: Widespread throughout North America; Yukon southeast to Toronto and Illinois, west to California. NESTING: Cleptoparasite of Colletes, which nest in the ground. IDENTIFICATION: Medium-sized black-and-white bee. HEAD: Dark, though the mandible is orange. The antennae are dark, though the first flagellar segment is slightly lighter in color. In females,

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Triepeolus  325 There are white the second flagellar segment is longer than it patches on the is wide. THORAX: On the scutum, there are sides of T2. distinct white hairs that outline the scutum (both anteriorly and posteriorly), as well as the scutellum. The axillae are small, barely extending to the middle of the The antennae are dark in this scutellum. The axillae species. and scutellum are both black. LEGS: The legs are light White hair rims each section orange. ABDOMEN: The center of of the thorax. T1 has a rectangular black area, T1 and T2 are Epeolus minimus and the apical white hair band interrupted at (female) the center. on T1 is interrupted at the center. The second through fourth tergal segments also have white apical hair bands that are slightly interrupted at the center, and T2 also has white round patches of hair on the sides. SIMILAR SPECIES: Epeolus minimus is similar to E. olympiellus and E. banksi. Epeolus olympiellus has a smaller range, Epeolus minimus occurring only in the Pacific Northwest. (male) Epeolus banksi is only on the East Coast, and the hair is more gray than ivory or white, as in E. minimus. The hair bands on T3 and T4 in E. olympiellus are much more interrupted at the center than those in E. minimus.

TRIEPEOLUS — SUBFAMILY: Nomadinae — TRIBE: Epeolini OVERVIEW: Medium-sized bees; matte-black bodies with bold white stripes made of matted hair. Cleptoparasites on Melissodes and other fall-flying Eucerini. No floral preferences, as they do not collect pollen; frequently seen hovering near the ground where their hosts may be nesting. In the evening and early morning may be found grasping plant stems with their mandibles, legs tucked up beneath the body. IN THE WORLD: There are more than 140 species of Triepeolus around the world. Absent from Africa, central Asia, India, and Australia, but found in South America, Europe, northern Asia, and North America. There are more than 100 species north of the Mexican border. More than 80 of these occur in the western U.S. and Canada.

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326  Apidae

HOSTS: Melissodes, other Eucerini. IDENTIFYING FEATURES: Matte-black bee with striking white patches of appressed

hairs running across the abdomen and thorax. HEAD: Face is wider than it is long and covered with thick or thin very matted hairs. Antennae are stout, and flagellar segments are black, but in some species the scape and pedestal are red. On the mouthparts, if they can be seen, the maxillary palpi consist of three segments. THORAX: Axillae at the posterior end of the scutum are sharply pointed and protrude posteriorly over the scutellum almost to the propodeum. Hair patterns on the scutum are bold, and many species appear as though they have a “smiley face” stamped on them. WINGS: Marginal cell is long and narrow. LEGS: Often red, or with reddish areas. ABDOMEN: Variously striped with stark white flattened hairs. Pseudopygidial area is long; often longer than it is wide. SIMILAR GENERA: Looks very similar to Epeolus and may be indistinguishable without viewing the genitalia. Overall, Epeolus are smaller, and there are differences in the pygidial plates that can help (see Epeolus for more information). On the wings, the marginal cell of Triepeolus is narrower and longer than that of Epeolus; both genera would need to be on hand to see the difference.

— Triepeolus subnitens SIZE: Medium; 11–15 mm. PHENOLOGY: May through early October. FLORAL HOSTS: Generalist when visiting flowers for nectar; does not collect pollen. RANGE: Across the West; rare in the Great Basin and Columbia River Basin. HOST: Has been observed entering nests of Svastra. IDENTIFICATION: Black-and-white to pale yellow bee with red legs. HEAD: The mandible is red at the base, as are the scape and pedicel. The clypeus is polished, with large and distinctive punctures, and no central line evident in the sculpturing. THORAX: The thorax is shiny. Each plate is outlined by thin flat white hairs, and two thin lines of white hair extend onto the anterior half of the scutum. The scutellum has two small crescents at the posterior end, and the axillae have triangular spines, gently rounded and narrow.

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Triepeolus subnitens (female)

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Triepeolus  327 LEGS: Legs are a rusty red. ABDOMEN: The first tergal segment has a patch in the center, almost rectangular, surrounded by flattened white to off-white hairs. Second tergal segment is dark at the base, with an enlarged black area centrally. The third through fifth tergal segments are dark at the base, and white at the apex. In females, the pseudopygidial area is short and wide, and covered Triepeolus subnitens (male) in long fine flattened hairs. In males, the pygidial plate is wide. SIMILAR SPECIES: Very similar to T. penicilliferus, and the two species share similar ranges, though T. penicilliferus is more common in Texas, while T. subnitens is more common further west. Triepeolus penicilliferus females have a narrower pseudopygidial area. Males are especially difficult to distinguish; often, T. subnitens has a brown pronotal lobe in males, while it is red in T. penicilliferus.

— Triepeolus remigatus SIZE: Medium;

10–14 mm. Late May through September. HOSTS: Eucera pruinosa, Eucera strenua, and Dieunomia heteropoda. RANGE: Coast to coast; absent from the Great Basin and northern Plains, but common throughout the Southwest. IDENTIFICATION: Matte-black bee with considerable white appressed hairs over entire body. HEAD: Face wider than long, shinier than other Triepeolus. The bases of the antennae may be reddish. THORAX: Pronotal collar is covered in thick, dense, ivory to white hair. The edges of the scutum are lined in a wide rim of appressed hair. Two lateral lines run down from the pronotal collar, which they touch, to either side of center. The posterior edge of the scutum is also lined with white hair, creating a central black area that looks like a head of broccoli, when viewed with the head aimed down. The tegulae are black. ABDOMEN: The first tergal segment is almost completely coated in yellow appressed hair, with a rhombus of black at the center, and a smaller triangle of black at the apex of the segment. In females, T2 has a wide semicircle of black at the base. Also in females, T3 and T4 have very wide hair bands that narrow only slightly in the center. The fifth tergal segment has two areas of light-colored appressed hair, laterally, and one brown area at the middle, along the apex; this hair is thicker and denser than the lighter-colored hair. In males, T2 is mostly black, surrounded by white hairs laterally and basally. PHENOLOGY:

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328  Apidae Distinct pattern on the thorax, often described as an anchor or like a head of broccoli.

SIMILAR SPECIES: Several Triepeolus species may look somewhat similar to T. remigatus, but this is the only species with its unique hair pattern on the scutum. Triepeolus concavus has yellow hair at the anterior half of the scutum, but this hair does not extend into two parallel lines. In addition, it does not have a triangle of black at the apex of the first tergal segment.

Two areas of black on T1

Triepeolus remigatus (female)

Triepeolus remigatus (male)

ERICROCIS — SUBFAMILY: Apinae — TRIBE: Epeolini OVERVIEW: Striking larger bees, usually with black-and-white patterning on the abdomen and often the thorax. Though rarely seen, they are hard to miss when they occur. Ericrocis are cleptoparasites of the also striking Centris. Little is known about Ericrocis. They nest in the ground, because their hosts do, and are common on summer plants with copious nectar. IN THE WORLD: Only four species of Ericrocis have been described, though a few undescribed species likely exist. In the U.S. there are two species, both restricted to the southwestern U.S. (occasional Kansas and Florida records). HOSTS: Centris. IDENTIFICATION: Striking, rather large, black-and-white bee. HEAD: Large eyes, with parallel sides. Face may be white beneath light hairs on middle of face. Antennae

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Ericrocis  329

relatively thick and shortened. THORAX: Often with patches of white appressed hair on scutum, scutellum, and metanotum. WINGS: Dark, long. The second and first recurrent veins meet the ends of the second and third submarginal cells almost exactly on. The marginal cell extends well beyond the end of the third submarginal cell. LEGS: The midtibial spur is forked, or with multiple teeth. There are no scopal hairs in females. ABDOMEN: The anterior and dorsal faces of T1 round gently from one to the other, with no distinct carina, though hair may make the delineation between the two appear ridgelike. Black and white flattened hairs occur in various patterns across the tergal segments. In females, the pygidial plate is well defined only right at its apex. SIMILAR GENERA: Few bees in North America have a similar appearance to Ericrocis, with its striking hair patterns and larger size. At first glance, Brachymelecta and Melecta may appear similar, but both those genera have a marginal cell that is short, ending just behind the apex of the third submarginal cell.

— Ericrocis lata SIZE: Medium; 11–14 mm. PHENOLOGY: May through October. FLORAL HOSTS: This bee is a cleptoparasite; it collects no pollen but will visit any number of flowering plants for nectar. RANGE: Southwestern U.S., north to Kansas, Utah, and Nevada. NESTING: Lays eggs in Centris nests. IDENTIFICATION: Conspicuous black-and-white to light red bee seen infrequently in the summer. HEAD: Wide, dark, with stout dark brown antennae. The scape is considerably wider at its apex than at its base. Clypeus flat, when viewed from the side, covered in minute pits, close and fine, beneath dense white hair. Vertex shining and bare. THORAX:  There is a little groove down There is a groove down the center the center of the thorax. of the scutum, splitting the minute and very densely crowded pits. WINGS: Smoky, darker toward the wing tips.

Ericrocis lata (female)

Wings are darker, and seem long relative to body.

Appressed white hair on thorax Patches of hair on the sides of each segment

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330  Apidae LEGS: Largely

covered in black hair. on tergal segments is small and very crowded. In females, Ericrocis lata (male) the pygidium is indefinite, so that only the apex is clearly visible. Apical areas of T2–T5 covered with white to yellowish appressed hair on each side. SIMILAR SPECIES: There is one additional species of Ericrocis in the U.S. They overlap in New Mexico and Arizona. The first flagellar segment is shorter, relative to the second, in E. pintada, while it is closer to the same length in E. lata. The propodeal area of E. pintada is roughened, while it is smooth in E. lata. ABDOMEN: Punctation

HOLCOPASITES — SUBFAMILY: Nomadinae — TRIBE: Ammobatoidini OVERVIEW: Small parasitic bees seen in the summer. They are relatively rare and seldom seen unless in the vicinity of a nesting site for their host. No floral preferences, and as often seen hovering above the ground looking for nest entrances as seen on flowers. IN THE WORLD: Nineteen species are currently recognized; all occur in North America. Most are found in the western U.S. HOSTS: Andrenidae (Calliopsis, Pseudopanurgus, Protandrena, other Panurginae). IDENTIFYING FEATURES: These are small pointy-ended bees covered in tiny rough punctures. HEAD: Antennae are located low on the face, just above the clypeus and clearly on the lower half of the face. THORAX: With white flattened hairs often in patches that look like spots. WINGS: Two submarginal cells. ABDOMEN: Red, or red and black, often with patches of flattened white hair. Males have a large pygidial plate, while females do not. SIMILAR GENERA: Sphecodes have similar coloration between the thorax and the abdomen, but have three submarginal cells. Ashmeadiella can also be similarly colored, with white patterning on a red abdomen, and also have two submarginal cells. Female Ashmeadiella collect pollen on their abdomen, so scopal hair should be visible on those individuals. In both males and females of Ashmeadiella, the head is much thicker, with a strong preoccipital carina, and the hair is not appressed as in Holcopasites.

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Holcopasites  331

— Holcopasites arizonicus SIZE: Small; 4–8 mm. PHENOLOGY: July– September. FLORAL HOSTS: Cleptoparasite. Visits flowers for nectar, but not pollen. RANGE: Southeast California east to New Mexico, north to Idaho. Most common in the Rocky Mountains. NESTING: Nests are in ground, in Calliopsis nests. IDENTIFICATION: Small ghostly gray bee with a reddish abdomen. HEAD: Black, with white closely appressed hair. Above the antennae, dense and closely punctate, not polished or shining. Ocelli close together, separated by Very rough scutum with dense pits less than twice their diameters. Antennae and mandibles reddish. Patches of white flattened hairs around antennal sockets. Eyes covered in short dense hair. In males, the first flagellar segment at least as long as second and third segments combined. THORAX: Black, Holcopasites arizonensis with white flattened hair. (female) Tegulae are red. Scutum coarsely White hair patches on T2–T4, pitted. LEGS: Reddish to brown. Spur but no complete bands on any of the tergal segments on midleg about half as long as basitarsus. ABDOMEN: Metasoma reddish, sometimes dark in the center. The second through fourth tergal segments with white band of hair on either side of the center. On the fourth tergal segment the band of hair is shortened, a dot to either side of center. Pygidial plate shortened. SIMILAR SPECIES: There are only a few Holcopasites arizonensis species of Holcopasites that have dense (male) hair on their compound eyes. Holcopasites arizonicus appears similar to H. rozeni, and they may overlap at the very southern end of the range of H. arizonicus. Holcopasistes rozeni has a complete band of white hair running across the fourth tergal segment, not interrupted or appearing as two spots, as in H. arizonicus. It also appears similar to H. insoletus, but that species is polished and lacking pits above the antennae.

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332  Apidae

MELECTA — SUBFAMILY: Apinae — TRIBE: Melectini OVERVIEW: Often brightly colored cleptoparasites, usually associated with nests of Anthophora. Not frequently seen. No floral preferences for these bees, which visit flowers only for nectar. Occasionally seen near ground-nesting sites of gregarious Anthophora. IN THE WORLD: Melecta occur in the Northern Hemisphere. There are 60 species in all, split into 5 subgenera. Only two of the subgenera occur in North America, and one has just one species (Melectomimus). Six species occur in Canada and the U.S. HOSTS: Anthophora and Habropoda. IDENTIFICATION: Large bee with contrasting hair patterns on thorax and abdomen. HEAD: There are either five or six segments to the maxillary palpi. Clypeus hangs down below a line drawn between the bottoms of the compound eyes. The compound eyes bulge slightly, sticking up above the line of the vertex, and appearing to aim forward more than other bees. THORAX: Thickly covered in gray, red, or tawny hair. The anterior half of the scutum appears raised, giving the bee the look of being hunched over, and making the head appear much lower in relation to the thorax than other bees. The scutellum is strongly arced, rather than sloping gently toward the propodeum. WINGS: Three submarginal cells. Marginal cell is short, ending where the submarginal cells do, and is gently rounded at the margin of the wing. Wings have small hairs outside of cells, as in Anthophora. LEGS: Arolium present. The tarsal claws are forked, with the inner portion long and slender. ABDOMEN: Typically dark colored; some species have gray, brown, or orange hair on T1, and a few species have small white patches of hair laterally on T2–T4, but overall the abdomen appears dark. The abdomen appears heavily tapered. In males, there is no pygidial plate. SIMILAR GENERA: Melecta look similar to their hosts, the Anthophorini. Females can be distinguished from both by the lack of scopal hairs. Few Anthophorini are solid black on T2–T4, usually sporting bands of white hair. Male Anthophorini have yellow on the clypeus, which is lacking in Melecta species. Other large Apidae may appear superficially similar (Eucerini, Bombus). Bombus always have some yellow on the abdomen, which isn’t found in Melecta. And Eucerini have hairs in the wing cells, which are lacking in this genus. Melecta also appear very similar to Brachymelecta, to which they are closely related. The inner tarsal claws are not inflated in Melecta, as they are in Brachymelecta. And the maxillary palpi have five or six segments. In addition, in males, the antennae are roughly as long as they are wide in Melecta, while in Brachymelecta they are significantly thicker.

— Melecta edwardsii SIZE: Medium; 11–14 mm. PHENOLOGY: Early March through April. FLORAL HOSTS: No floral hosts; the bee is a cleptoparasite. RANGE: Nevada and California. NESTING: Females lay eggs in ground nests of Anthophora.

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Melecta  333

Two large spines on scutellum

Melecta edwardsii (male)

Melecta edwardsii (female)

IDENTIFICATION: Robust bee with black abdomen and tawny hairy thorax. HEAD: Hair is mostly black, though some light-colored hairs can be seen on the vertex. Though hard to see, the maxillary palpi are six-segmented, and the fifth and sixth are about the same length. THORAX: There are two very long spines on the sides of the scutellum that can be seen through the hair. Hair on scutum and scutellum is light tan. Hair on the side of the body, beneath the wings, is black. ABDOMEN: There is no hair of the same color as that on the thorax on T1. In females, the pygidial plate is broad, so that it covers the whole surface of T6. SIMILAR SPECIES: The spines on the scutellum of M. edwardsii are unique among all the Melecta species in North America. This character can distinguish the bee from all other species.

— Melecta pacifica SIZE: Medium; 12–13 mm. PHENOLOGY: April through July. FLORAL HOSTS: No floral hosts; the bee is a cleptoparasite. RANGE: Occurs across North America, with several subspecies. More common in the West, where it ranges from the Rocky Mountains west to the California coast, north to southern Alberta, and south to the Mexican border. NESTING: Females lay eggs in ground nests of Anthophora. IDENTIFICATION: Striking large bee with a dark abdomen, and often brightly colored thorax. HEAD: In males, the clypeus is covered with black hair. In males, the flagellar

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334  Apidae

segments are smooth, with no deep pits on the side that faces the head. In females, the first and second flagellar segments are about the same length. In both sexes, the vertex of the head is roughened, and not shiny. THORAX:  Covered in thick orange to red hairs (in M. pacifica fulvida and M. p. atlantica), or gray hairs (in M. p. pacifica). LEGS: The outer surface of the mid and hind tibiae are covered with black hair. ABDOMEN: The hair on T1 is the same color as that on the thorax of the bee. The other tergal segments are all entirely black. In females, the pygidial plate is narrow and parallel-sided, very narrowly rounding at its apex. In males, T7 has a deep notch in it, right at its apex. SIMILAR SPECIES: There are several Melecta pacifica subspecies in M. pacifica, which differ (female) primarily in the coloration of the dense hair on the thorax. Few species There are several subspecies of this bee, and they differ primarily in the color of the hairs on the thorax. M. p. pacifica is gray, instead of red, as in this M. p. fulvida. Melecta pacifica atalantica is also red. T1 is all red.

Melecta pacifica (female) pygidial plate is narrow parallel-sided

Melecta pacifica (male)

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Zacosmia  335

lack white patches on the abdomen and have hair on T1 that is the same as the hair on the thorax. Altogether, M. pacifica most closely resembles M. thoracica. Males can be distinguished because of the absence of deep pits on the side of the antennae that faces the head, and the shape of T7, which is truncated in M. thoracica. With females, M. thoracica has a smooth triangular area on the vertex that is highly polished; this is not present in M. pacifica. Also, the pygidial plate of M. thoracica is triangular, rather than parallel-sided.

ZACOSMIA — SUBFAMILY: Apinae — TRIBE: Melectini OVERVIEW: Striking black-and-white bee with very thick antennae. This bee is short and stocky; it stands out when seen, but it is relatively uncommon. It is a cleptoparasite on smaller species of Anthophora. IN THE WORLD: Zacosmia occurs only in the Northern Hemisphere from southern Canada through Mexico. There is one known species. HOSTS: Anthophora, especially those in the subgenus (Heliophila), which are smaller species. IDENTIFYING FEATURES: White and black (or brown bee) of smaller size. HEAD: Though hard to see, the maxillary palps are extremely short, and only one- to three-segmented. In males, the antennae are very thick, with each segment more than twice as wide as long; overall, male antennae appear to taper at both ends. THORAX: Hair is appressed, patterned as dark spots and bands on a pale background. LEGS: There are no arolia. WINGS: Three submarginal cells. The marginal cell is barely longer than the stigma. There is some variability in the wing venation so that the number of submarginal cells can vary, even between the two wings on the same bee. ABDOMEN: In males, the pygidial plate is present. SIMILAR GENERA: The abnormal antennae on males of this bee are quite distinctive and make them easy to distinguish. For females, the short marginal cell and the appressed black-and-white hair patterns are also unique.

— Zacosmia maculata SIZE: Small; 5–9 mm. PHENOLOGY: May through August. FLORAL HOSTS: No floral hosts; the bee is a cleptoparasite. RANGE: Occurs all across western North America, from southern Alberta to the tip of Baja, and into Durango and Chihuahua, Mexico; east as far as Wyoming. NESTING: Females lay eggs in ground nests of Anthophora (Heliophila). IDENTIFICATION: Striking, but small, black and white bee. There is only one species of Zacosmia

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336  Apidae Zacosmia maculata in the world; see (female) the genus description for most characters. ABDOMEN: The hair on the abdomen is all appressed, with wavy white bands running across each segment. Each band dips at its center, looking like a drip of white paint. SIMILAR SPECIES: There are two subspecies of Z. maculata; they differ in the coloring of the legs, scape, tegulae, and pygidial Antennae are very thick. area, which are redder in Z. m. desertorum, but tend to be brown or black in Z. m. maculata.

Appressed black and white hair pattern is unique.

Short marginal cell

Zacosmia maculata (male)

BRACHYMELECTA — SUBFAMILY: Apinae — TRIBE: Melectini OVERVIEW: Striking, slender, black-and-white bees. Rarely seen cleptoparasites of bees in the Anthophorini, including Anthophora and Habropoda. IN THE WORLD: There are fewer than 10 species of Brachymelecta in the world, all restricted to North America and the West Indies (three species in Panama, Cuba, and Hispaniola). Three species are found in the xeric Southwest, with two of them having ranges that extend as far north and east as Minnesota. HOSTS: Anthophora and Habropoda. IDENTIFYING FEATURES: Black body with short hairs on the abdomen, but with the thorax bare. HEAD: Though hard to see except in pinned specimens, there are four or five short maxillary palpi. Antennae thin in both males and females. Clypeus sticks out strongly. THORAX: With thick fluffy hair, not appressed as in many cleptoparasites. May be brightly colored. WINGS: Three submarginal cells. Long marginal cell—longer than stigma—but rounded at its apex. Cells lack hairs, but hairs are present between the cells and the outer edge of the wing. LEGS: Arolia present. Tarsal claws modified, so

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Brachymelecta  337

that the inner tooth looks inflated. In males, the hind legs are simple, with no modifications. No scopae on hind legs in female. ABDOMEN: Tergal segments black with patches of white hair. In males, the sterna lack any brushes of black bristles. Pygidial plate absent in males. SIMILAR GENERA: Few bees look like Brachymelecta; other cleptoparasites of similar size and coloration have two submarginal cells. The exception is Melecta, which is closely related. In Melecta the marginal cell is significantly shorter. The hind legs of male Melecta are often modified, and there are black bristles on the sterna in males. NOTE: For many years, Brachymelecta was considered the rarest bee in North America. Only one specimen had ever been collected, by H. K. Morrison in 1878, somewhere in Nevada. In a 2021 paper, scientists describe how they figured out that this Brachymelecta specimen is actually an uncommon variant of Xeromelecta californica, a much more common species in a common genus. However, since the name Brachymelecta is the older name for this group, rather than just renaming the one rare specimen, the entire genus was rechristened with the older name for bees with these characteristics. Thus, all Xeromelecta are now Brachymelecta.

— Brachymelecta californica SIZE: Small

to medium; 8–14 mm. through July. FLORAL HOSTS: No floral hosts; this species does not collect pollen. It is a cleptoparasite of Anthophora, with specific records on A. abrupta. RANGE: The Mexican border north to British Columbia, Iowa, and Virginia. IDENTIFICATION: Striking bee with black-andwhite patches on the abdomen. HEAD: Dark, with little hair. The clypeus sticks out notably from the head. THORAX: On the scutellum, there are two short, barely projecting spines. The upper part of the thorax is covered in Brachymelecta californica (female) pale hair. Some of the pits at the center of the scutum are very large, larger than any seen on the rest of the scutum or the scutellum. LEGS: Dark to light rust colored, with thick appressed hairs on some segments. ABDOMEN: In females, on T1 and T2, there are thick bands of white woolly hair running the width of the segment, thin at the center and thicker to the sides. On T4 there are white rounded circles of white PHENOLOGY: May

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338  Apidae Brachymelecta californica

hair on the sides. In males, T1–T5 (male) have broad thick bands of appressed white hair, slightly thinner at the center. SIMILAR SPECIES: There are three species of Brachymelecta in the U.S. Brachymelecta larreae, which is found only in the hot deserts of the Southwest, has thick red hair on thorax and a black abdomen. The wings are long, and very dark. Brachymelecta interrupta is found primarily in the Midwest, west as far as the White Mountains in Arizona, and east to Indiana. In this species the pits on the scutellum and the scutum are all the same size.

NEOLARRA — SUBFAMILY: Nomadinae — TRIBE: Neolarrini OVERVIEW: Diminutive bees with frosty coating of appressed hairs. Cleptoparasites of Perdita species. Very rare, and usually restricted to arid sandy regions. Usually seen as they fly erratically over the Earth’s surface. IN THE WORLD: There are 14 species of Neolarra, all concentrated in North and Central America. The species occur north of the Mexican border, concentrated in the desert Southwest. HOSTS: Perdita. IDENTIFYING FEATURES: Small discreet bees. HEAD: Oval head, wider than long, with thick, short, dense hair coat. The gena is thick, almost as thick as the compound eye. Antennae are short and stocky. In males, there are 10 flagellar segments, as in females. This is the only bee genus with this characteristic in males. THORAX: Axillae may be produced into sharp angles, or short and rounded. Scutum is wider than the scutellum, which narrows from the anterior to posterior end in some species. WINGS: The wing venation is unique, not extending beyond the middle of the forewing. The marginal cell is incredibly shortened, barely longer than the stigma. There are only two submarginal cells, and the second one is very short, or even absent. ABDOMEN: The abdomen is often red and may have short appressed bands of hair running across it. There is no pygidial plate in males or females, but females may have a notch at the center of the apex. In males, T7 has a short protrusion at the center. SIMILAR GENERA: There are few genera that look anything like Neolarra, anywhere in the world. The appressed hairs, tiny size, and unique wing venation are all telling.

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— Neolarra californica SIZE: Petite; 3–4 mm. PHENOLOGY: August and September. FLORAL HOSTS: Cleptoparasitic bee; visits flowers for nectar but not pollen. RANGE: Nevada to Texas, north to central Utah. NESTING: Parasitizes Perdita, so likely nests in the ground. IDENTIFICATION: Very tiny, very rare bee, a cleptoparasitic bee. HEAD: The top ocellus is pushed slightly forward. In males, the first flagellar segment is shorter than the pedicel; about as broad as long. THORAX: Axillae are not narrowed, but broadly arcuate. ABDOMEN: In females, abdomen is light red, clearly visible through the white appressed hairs. In males, abdomen is black. In males, T7 is slender. In females, apical margin of T5 has a deep central notch. SIMILAR SPECIES: The female appears similar to Neolarra alba, which also has a deep notch on T5. The notch is much bigger on N. alba than Neolarra californica on N. californica. In males, the (male) protrusion on T7 is much narrower in N. californica. In addition, the hind tibial spurs of N. californica are about half as long as the tarsi, while in N. alba they are about two-thirds the length of the tarsi.

Neolarra californica (female)

OREOPASITES — SUBFAMILY: Nomadinae — TRIBE: Ammobatini OVERVIEW: Petite bees with red abdomens, seldom-seen cleptoparasites of bees in the genera Perdita and Calliopsis but may parasitize other panurgines as well. This is the only representative of the tribe Ammobatini that is found in the Western Hemisphere. Nest in the ground, where their host bees are found; while rarely seen, they have been seen in abundance near nesting sites of their hosts, where they fly low over the nest entrances.

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IN THE WORLD: Oreopasites are found only in western North America. There are 11 species in all, with 10 occurring north of the U.S.-Mexico border. All 10 are found in the western U.S. HOSTS: Calliopsis and Perdita. IDENTIFYING FEATURES: Very small bees with dark brown or black head and thorax, and red abdomen. HEAD: Dark head, long antennae. THORAX: Some sparse hair occurs on thorax, may be white, but it is not appressed or flattened as in other cleptoparasites. WINGS: Two submarginal cells. Marginal cell is rounded or truncated at its apex. Beyond the cells of the wing, there are hairs. LEGS: Arolia present. There are no scopae on the legs. ABDOMEN: There are no scopae on the abdomen. In females, there is no pygidial plate. In males, there is a pygidial plate. SIMILAR GENERA: With the red abdomen and dark head and thorax, Oreopasites may look similar to Sphecodes. Sphecodes have three submarginal cells, and the marginal cell is long and thin, rather than round, as in Oreopasites.

— Oreopasites vanduzeei SIZE: Petite to small, though size varies significantly; 3.5–6.6 mm. PHENOLOGY: May through August. FLORAL HOSTS: No floral hosts; this species does not collect pollen. RANGE: Oregon east to Wyoming, south to New Mexico and Baja. Absent from the Colorado Plateau; most common Oreopasites in California. NESTING: Ground nester, in nests of Calliopsis. IDENTIFICATION: Extremely small red-and-black bee. HEAD: The clypeus is long and slightly protuberant, extending slightly below the lower margins of the compound eyes. Though not visible without a microscope, the maxillary palpi have six segments, with the most basal one extremely small. THORAX: The scutum is covered with even pits of moderate density, which do not become denser in the center. ABDOMEN: In females, the fifth sternal segment has a band of hair that is interrupted at the center.

Two submarginal cells Oreopasites vanduzeei (female)

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Oreopasites vanduzeei (female)

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SIMILAR SPECIES: This is the most widespread of the Oreopasites species that are found in the U.S. The clypeus is longer in O. vanduzeei compared with other species in the genus, it is smaller than some other species, and tends to be covered in more plumose hair; that aside, Oreopasites species can be difficult to distinguish, especially in California.

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Oreopasites vanduzeei (male)

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342  Apidae

A KEY TO BEE GENERA IN WESTERN NORTH AMERICA

What follows is a dichotomous key to the bee genera of western North America. Before you use this key to identify the genus of your insect, make sure that you are looking at a bee specimen. Look for four wings (two on each side) to rule out flies. Look for three unique and separate body parts (in this book referred to as head, thorax, abdomen). Make sure there are no metallic silver-colored hairs on the face, and that the first segment of the abdomen is not elongated and thin. And look for the presence of branched hairs; these are usually present in multiple areas of the bee’s body, but if in doubt, make sure to look near the pronotal lobe and on the propodeum. A few notes on how to use a dichotomous key. First, information is presented in a series of couplets, as either/or statements. Read both parts of a couplet completely before making a decision. Remember that a bee must match all the information in a couplet, and not just some of it, unless explicitly stated as an either/or. Information is presented in a couplet in order from most important, and easiest to see, to least important, or most difficult to see. If, after reading both parts of a couplet, you are not sure which is more appropriate, try both. Run the bee through both parts. As the characters in other couplets are presented, it may become clear that the bee at hand does not fit the chosen path, and you can go back and try the other side of the couplet. Note also that characters presented in a couplet are not exclusive, in the sense that they apply only to the bees that will resolve in that couplet, and not to any that were broken out before that point. For example, if a couplet identifies Anthidium from other Anthidiini on the basis of its arolium, this does not exclude other bees that are not mentioned in the couplet from also having an arolium. 1 a. Scopae No scopal hairs evident on either the abdomen or the legs ..............................................................................parasitic bees, males, and Hylaeus ▸ Go to 2

b. Scopae Evident on either the hind tibiae and/or hind femurs, or the ventral surface of the abdomen. Scopal hairs may be difficult to discern from other hairs that are long; look for pollen grains embedded in hairs.

If unsure, go to 2....................................................................... nonparasitic bees / ▸ Go to 3

2 a. Head 13 antennal segments, many of which may be elongated. Abdomen  Consists of 7 exposed tergal segments. No apparent sting

(be careful not to mistake the mid-apical projection that sometimes occurs on T7 as a sting!)................................................................................ males ▸ Go to 58

b. Head  12 antennal segments.

Abdomen  Consists of 6 exposed tergal segments. Possesses a sting; this

may not be visible if it is retracted.......................... parasitic bees and Hylaeus / ▸ Go to 130

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3 a. Hind leg  Hind tibia possesses a corbicula. It is polished, flattened, and hairless, but surrounded by a fringe of hairs that curl toward its center. Depending on the genus, may be greatly enlarged (Figure 1). ....................................... corbiculate bees (but not Bombus subgenus Psithyrus) / ▸ Go to 4

b. Hind leg  Hind tibia does not form a corbicula. It is variously shaped, but not flattened, hairless, or with a fringe of hairs curling in.............................................. ▸ Go to 5 Corbicula

Figure 1 No tibial spur

4 a. Hair Tan, amber, or dark hairs, but no yellow hairs on body. Head  Hairs protrude from the compound eyes (Figure 2). Wing  Marginal cell is long, extending almost to the apex of the wing. There is a pronounced jugal lobe on the hind wing (Figure 3). Hind leg  Tibial spurs are absent (Figure 1).................................................... Apis mellifera /

Figure 2



Figure 3

b. Hair Some combination of yellow and black hair; may also include red or white stripes.

Head  Compound eyes are not hairy. Wing  Marginal cell is slightly long, but on the hind wing, there is no jugal lobe (Figure 4). Hind Leg  Tibial spurs are evident (Figure 5)................................. pollen-collecting Bombus /

Figure 4

Figure 5

Corbicula

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Tibial spur

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344  A KEY TO BEE GENERA IN WESTERN NORTH AMERICA

5 a. Scopal hairs  Present on the underside of the abdomen, but not on the hind legs. Wing  Two submarginal cells...................................... nonparasitic Megachilidae / ▸ Go to 6

b. Scopal hairs  Present on the hind leg; may be simple with few branches, or dense and heavily branched. The abdomen may have a few scopal hairs laterally on T1, but overall lacks scopal hairs.

Wing  May have two or three submarginal cells...................................................... ▸ Go to 18

6 a. Head Large knobs protrude from between the antennal sockets (Figure 6). Mandible  Has three teeth, with the middle one longer than the others (Figure 6). Leg  Numerous bumps (tubercles) on the outer surfaces of the hind tibiae, similar to crab legs on your dinner plate (Figure 7). Arolia absent between front claws. Abdomen  Pygidial plate reduced to small apical spine.................................... Lithurgopsis /

Figure 6

Figure 7

Three teeth, middle one longer



b. Head No large knobs are evident between the antennal sockets.

Mandible  May have any number of teeth, but the middle tooth is not significantly longer than the others. Leg  No tubercles on surface of the hind tibiae. An arolium may be present or absent. Abdomen  Pygidial plate present or absent, but not reduced to a small apical

spine........................................................................................................................... ▸ Go to 7

7 a. Integument Body with at least some yellow, ivory, and/or red markings, especially on the abdomen. In most species these markings are abundant and evident, but in a few species, the yellow or ivory maculations are restricted to the abdomen. Leg  Tarsal claws are split or cleft. Wings  Stigma is longer; this character is hard to judge without two bees side

by side.............................................................................. nonparasitic Anthidiini / ▸ Go to 8

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b. Integment Body matte black, or metallic blue or green, but never with yellow, ivory, or red maculations; however, hair may be colored yellow and red.

Leg  Tarsal claws are whole. Wings  Stigma is elongated..................................................................................... ▸ Go to 12

8 a. Leg No arolium between the claws (Figure 8). Head  Mandible has at least five teeth, usually six or more; many are small

(Figure 9).............................................................................................................. Anthidium /

b. Leg Arolium between the tarsal claws.

Head  Mandible has fewer than five teeth. ............................................................... ▸ Go to 9

Figure 8

3 2 1

4

5

Figure 9

9 a. Thorax On the side of the thorax, the face that wraps from the side of the body around to the front (called the mesopleuron) is sharply angled, so that it looks like the edge of a box (strong omaular carina) (Figure 10). .................................................................................................................................. ▸ Go to 10 Note: One Dianthidium species (D. texanum) that is rarely seen in the Midwest and Southwest and not included in this book does not have a strong omaular carina.

b. Thorax On the side of the thorax, the mesopleuron is not sharply angled, but rounds gently from the lateral to the anterior face (Figure 11). .............................. ▸ Go to 11

10 a. Head Subantennal suture curves strongly outward before connecting to clypeus. Strong preoccipital carina (Figure 12). Thorax  Scutellum extends posteriorly (backward) over the metanotum and pronotum as

a broad shelf. Pronotal lobe may have a small carina, but it is not extended anteriorly as a nearly see-through plate (Figure 13)................................................................. Anthidiellum /

Figure 10

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Figure 11

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346  A KEY TO BEE GENERA IN WESTERN NORTH AMERICA

Figure 12

Figure 14 Figure 13

b. Face: Subantennal suture is a straight line between the antennal socket and the top of the clypeus (Figure 14). No strong preoccipital carina.

Thorax  Scutellum ends before the metanotum and does not overhang the

pronotum. Pronotal lobe very thin, almost see-through, and extending out toward the head (Figure 14). ........................................................................... Dianthidium /

11 a. Thorax Pronotal lobe very thin and see-through, but also short. Leg  Hind tibia is not covered with small, simple bristles. ........................... Paranthidium /

b. Thorax Pronotal lobe rounded, and not thin and see-through.

Leg  Hind tibia and basitarsus wide; both are covered in short stout hairs (Figure 15). ............................................................................................................... Trachusa /

12 a. Leg Arolia absent, always from hind legs, usually from all legs (Figure 16). ................................................................................................................................ Megachile /

b. Leg Arolia present (Figure 17)............................................................... Osmiini / ▸ Go to 13 Figure 15

Figure 16

Figure 17

Bristles on tibia

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13 a. Thorax Dorsal portion of propodeum lined with a series of large, deep pits, the posterior edge of which flips up as a carina, right before the posterior face (Figure 18). Abdomen  Anterior surface (forward facing) of T1 widely concave, with a strong

carina outlining the edge. Abdomen tends to curl strongly under in dead specimens. Each tergal segment appears to constrict apically, giving the sides of the abdomen a wavy look when viewed from above (Figure 19). ..................... Heriades /

Figure 18



Figure 19

b. Thorax No carina with deep pits at the margin of the dorsal and posterior faces of the propodeum.

Abdomen  Anterior surface of T1 is not concave, and the abdomen does not tend to curl strongly under in dead specimens. ..................................................... ▸ Go to 14

14 a. Thorax Parapsidal line is reduced to a small dot (Figure 20). Integument  Usually metallic, but some northern species may be black. ............... Osmia /

b. Thorax Parapsidal line is long, more than 3 times as long as it is wide (Figure 21).

Integument  Seldom metallic. ................................................................................. Figure 20

Figure 21

▸ Go to 15

Figure 22

15 a. Head Clypeus has a long spoonlike projection hanging down the center (Figure 22). ............................................................................................................. Protosmia /

b. Head Clypeus variously formed, but never with an elongate spoonlike projection hanging down in the center. .................................................................. ▸ Go to 16

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16 a. Thorax Narrow and very elongated, so that the portion of the scutum anterior to the tegulae is as long as the portion posterior to them (Figure 23). .......................................................................................................... Chelostoma /

b. Thorax Not elongated, the length of portion of the scutum anterior to the tegulae much less than the portion posterior to them. .........................................

▸ Go to 17

Figure 24

Figure 23

17 a. Thorax On the side of the thorax, the face that wraps from the side of the body around to the front (called the mesopleuron) is sharply angled, so that it looks like the edge of a box (strong omaular carina) (Figure 24). The anterior (forward-facing) portion of this plate is shiny and polished, while the lateral (side-facing) portion is punctate. ........................................ Ashmeadiella /

b. Thorax The mesepisternum rounds gently from the anterior to the lateral faces, and both are punctate to the same degree (Figure 25). ................................ Hoplitis / Note: The bee genus Xeroheriades, which is not featured in this book, will also key out here. It can be distinguished by the fact that T1–T3 curve in at the middle, along their apical margin.

18 a. Head Two subantennal sutures run from each of the antennal sockets to the top of the clypeus (Figure 26).................................................... Andrenidae / ▸ Go to 19 Note: This may be hard to see in females of the subfamily Andreninae; verify by also looking for facial foveae and scopal hairs running up to the trochanters (see couplet 19).

b. Head One subantennal suture runs from each of the antennal sockets to the top of the clypeus. ................................................................................................... ▸ Go to 27

Figure 25

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Figure 26

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19 a. Head First antennal segment the same length, or longer than, the scape (Figure 27). No facial fovea. Wing  Stigma nearly absent. Marginal cell of forewing extraordinarily long (Figure 28).............................................................................................................. Protoxaea /

Figure 27



Figure 28

b. Head First antennal segment shorter than the scape, only occasionally the same length. Never longer. Facial fovea present. Depressions found beside compound eyes, usually filled with velvety hair (Figure 29).

Wing  Stigma present and obvious. Marginal cell of forewing much shorter, about half as wide as it is long (Figure 30).............................................................

Figure 29

▸ Go to 20

Figure 30

20 a. Wing Marginal cell is pointed, or very softly blunted. Its tip ends right at the wing margin (Figure 30). Leg  Scopal hairs are found on basitarsus, tibia, and femur, and longer curled hairs on trochanter; hairs can also be found on thorax on the propodeum. .............................................................................................................. Andreninae / Go to 21

b. Wing Marginal cell is not pointed or gently rounded; often abruptly cut off; if pointed, the point (apex of the cell) is away from the wing margin (Figures 31, 35, 36, 38, 39, 41).

Leg  Scopal hairs found primarily on tibia and basitarsus. ................................... ▸ Go to 23

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21 a. Abdomen The anterior surface of T1 is broadly concave (Figure 31). .......... Ancylandrena /

b. Abdomen The anterior surface of T1 has a tiny concavity, but it does not occupy the majority of the face (Figure 32). ........................................................... Figure 31

▸ Go to 22

Figure 32

22 a. Leg Hind basitarsus more than half as long as hind tibia (Figure 33). .............................................................................................................. Andrena /

b. Leg Hind basitarsus half or less than half as long as the hind tibia (Figure 34). ........................................................................................................ Megandrena /

23 a. Wing Marginal cell is often so truncate as to appear as a square. The stigma is enlarged, almost as big as the marginal cell (Figure 35). Two submarginal cells. Note: Some Panurginus have cells that look like this; see integument character for distinction. Integument  Metallic, often with yellow or red markings on the abdomen (may be extensive). Mandibles often yellow or white. Size  Minute: 4–8 mm. ........................................................................ Perditini / ▸ Go to 24

Figure 33

Figure 35

Figure 34

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Figure 36

Figure 37

Figure 38

b. Wing Marginal cell is variable, but never so truncate as to appear as a square, and with an enlarged stigma. There may be 2 or 3 submarginal cells. If the submarginal cell appears truncated, see integument character.

Integument  Dark areas of bee are matte; not metallic. If the submarginal cell is truncated, as in couplet 23a, this matte-black character is especially useful. Bee may have yellow on abdomen, and on tegula, leg joints, and pronotal collar, but black is the primary color. Size  Variable, but generally larger than 6 mm. ......................... other Panurginae ▸ Go to 25

24 a. Wing Stigma slender, not much (if any) wider than the prestigma (Figure 36). ............................................................................................................ Macrotera /

b. Wing Stigma large (Figure 35). ................................................................................. Perdita /

25 a. Head Anterior tentorial pit is along the outer subantennal suture and not at the junction of the epistomal suture (Figure 37). Eyes, especially of live specimens, appear a light blue. Wing  Stigma is small and often narrow, about the same size as the prestigma (Figure 38). Abdomen  S6 with tufts of dense, curving hairs at the apex. T6 usually covered with thick hair that obscures the integument. Other tergal segments may be lined apically with thin bands of sparse hair. ........................................... Calliopsis /

b. Head Anterior tentorial pit is at the junction of the epistomal and outer subantennal sutures.

Wing  Stigma is larger than prestigma. Abdomen  S6 without tufts of dense, curving hairs at the apex. T6 with only sparse hair; integument clearly visible beneath, especially basally. Tergal segments never have apical hair bands (may have basal hair bands, or hair bands across the middle of a segment). ...............................................................

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▸ Go to 26

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26 a. Wing First recurrent vein exactly meets the first transverse cubital (the vein separating the 2 submarginal cells) (Figure 39). Two submarginal cells. Thorax  On side of body, episternal groove is missing (Figure 40). ..................Panurginus /

b. Wing First recurrent vein meets the middle of the second submarginal cell, not exactly meeting the first transverse cubital (Figure 41). Two or three submarginal cells.

Thorax  On side of body, episternal groove is visible (Figure 42).....................Protandrena / Note: Pseudopanurgus also key out to Protandrena based on these characters; this is a group that is in flux, and some species of Pseudopanurgus have been reclassified as Protandrena. Also in this couplet would fall the rare genus Anthemurgus, which is found some in the Midwest and in the East. It looks like Protandrena except for very short mouthparts.

Figure 39

Figure 40

Figure 41

Figure 42

Figure 43

Figure 44

27 a. Wing Second recurrent vein is strongly curved, like an S (Figure 43). Abdomen  No pygidial plate (Figure 44).................................................................... Colletes /

b. Wing Second recurrent vein runs almost completely straight.

Abdomen  May or may not have a pygidial plate.................................................... ▸ Go to 28

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Figure 45

28 a. Wing Basal vein is strongly arced, rather than running as a straight line to the first submarginal cell (Figure 45)..................................................................................... ▸ Go to 29

b. Wing Basal vein is straight, not strongly arcing in toward the wing base before meeting the first submarginal cell................................................................ ▸ Go to 34

29 a. Head Usually a dot or line of yellow on clypeus. Tongue is long (Figure 46). Wing  Second submarginal cell is triangular, distinctly narrowing at the end nearest the wing margin. Abdomen  Pygidial plate absent, though the tip of T6 may taper to a point. Each tergal segment is slightly constricted, so that the abdomen appears to have wavy edges (Figure 47).................................................................................... Ceratina /

b. Head Never with yellow on the clypeus. Tongue is short, tapering to a point.

Wing  Second submarginal cell is more or less square. Abdomen  Often with hair bands running across the abdomen. Pygidial plate present. ................................................................... pollen-collecting Halictinae / ▸ Go to 30

Figure 46

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Figure 47

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30 a. Thorax Bright polished green (Figure 48). Abdomen  May be green, black, or yellow and brown............................................

▸ Go to 31

b. Thorax May be lightly metallic green or coppery, but not brilliantly so.

Abdomen  Brown, red, or black............................................................................... Figure 48

▸ Go to 33

Figure 49

31 a. Thorax The posterior surface of the propodeum is completely outlined by a strong carina (Figure 48). Head  Inner margin of compound eye without distinct notch near the level of the antennal sockets, runs smoothly from bottom of face to the top (Figure 49). ....................................................................................................... Agapostemon /

b. Thorax The propodeum gently curves to its lateral and dorsal surfaces, with no clear carina completely encircling the posterior surface (Figure 50).

Head  Inner margin of compound eye with distinct notch, usually just above the level of the antennal sockets (Figure 51). ..................................... Augochlorini ▸ Go to 32

Figure 50

Figure 51

32 a. Thorax Tegula is dented in on the interior side, forming a C shape; not symmetric (Figure 52). Leg  Basitibial plate is very short, to the point of being barely visible. Hind tibial spurs are shaped like a little comb, with wide teeth. Abdomen  Apex of T1 and T2 are lined with a row of short, stout, unbranched bristles (Figure 53)..................................................................... Augochloropsis /

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Figure 52

Figure 53

Figure 54

b. Thorax Tegula is oval in shape, with no indentations on the interior side.

Leg  Basitibial plate is rounded, and clearly visible. Hind tibial spurs are simple, or finely serrated (Figure 54). Abdomen  There is no row of stout bristles on either T1 or T2...................... Augochlorella / Note: Augochlora will also key out here based on these characters; it is a common genus in the East, but very rare in the West. It can be distinguished from Augochlorella by the presence of a strong lobe on the paraocular area that extends down over the clypeus, and the marginal cell, which is cut off at its apex in Augochlora.

33 a. Abdomen T1–T4 with strong, clearly evident bands of hair running across the apex of each. In worn specimens, this may be most visible on the sides of each tergal segment (Figure 55). Wing  The veins separating the first, second, and third submarginal cells from each other are always dark and strongly presented. ..................................... Halictus /

b. Abdomen T1–T4 either without any hair bands at all or if hair bands are present, they are at the base of each tergal segment, emerging from under the apical margin of the tergal segment before (Figure 56).

Wing  The veins separating the first, second, and third submarginal cells from each other may be weak (Figure 57)........................................................ Lasioglossum / Note: A few Lasioglossum have 2 submarginal cells. In those cases, the veins near the apex of the wing are the weaker. Figure 55

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Figure 56

Figure 57

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34 a. Head The antennal sockets are on the lower half of the face, below the midpoint of the inner margin of the compound eyes, and only about the width of one antennal socket above the top (base) of the clypeus (Figures 58, 59). ....................................................... pollen-collecting Rophitinae / ▸ Go to 35

b. Head The antennal sockets are higher on the face, occurring above or at the midpoint of the inner margin of the compound eyes, and appearing well above the top of the clypeus. ......................................................... ▸ Go to 39

Figure 58

Figure 59

35 a. Wing Two submarginal cells................................................................................... ▸ Go to 36

b. Wing Three submarginal cells................................................................................

▸ Go to 37

36 a. Head Clypeus protrudes notably from face, when viewed in profile. Wing  The distance from the end of the stigma to the end of the marginal cell is usually the same as the distance from the end of the marginal cell to the tip of the wing (Figure 60). ................................................................................... Dufourea /

b. Head Clypeus does not protrude from head notably when viewed in profile.

Wing  The distance from the end of the stigma to the end of the marginal cell is less than distance from the apex of marginal cell to the wing tip (Figure 61). ..................................................................................................... Micralictoides / Note: The rare Sphecodosoma beameri will also key out here; it is not described in this book. In that species the head and thorax are heavily pitted; Micralictoides has weaker punctation.

Figure 60

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Figure 61

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37 a. Leg Outer hind tibial spur and mid tibial spur with coarse teeth (Figure 62). ............................................................................................................. Xeralictus /

b. Leg Outer hind tibial spur with minute teeth. ....................................................... ▸ Go to 38

Figure 62

38 a. Thorax The dorsal portion of the propodeum is short, about 2/3 as long as the scutellum (Figure 63). .......................................................................... Protodufourea /

b. Thorax The dorsal portion of the propodeum is longer, about the same length as the scutellum (Figure 64). ............................................................. Conanthalictus / Note: The rare Sphecodosoma dicksoni will also key out here; it is not described in this book. In that species the thorax is smooth and shining between pits; Conanthalictus has a duller surface.

Figure 63

Figure 64

Figure 65

39 a. Abdomen Integument of tergal segments with iridescent, often pearlescent apical margin that is completely lacking in punctation or hairs (Figure 65). ........... Nomia /

b. Abdomen Tergal segments not iridescent or pearlescent, though there may be ivory or cream integumental markings. ............................................................

▸ Go to 40

40 a. Wing Two submarginal cells. ................................................................................. ▸ Go to 41

b. Wing Three submarginal cells...............................................................................

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▸ Go to 44

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41 a. Wing Marginal cell tapering to a rounded point (Figures 66, 67)........................ ▸ Go to 42

b. Wing Marginal cell not short, but ending abruptly with a downward angle (Figure 68)......................................................................................... Exomalopsini ▸ Go to 43 Note: The Exomalopsini key out in two different areas; some species have two submarginal cells, and some have three. Figure 66

Figure 67

Figure 68

42 a. Abdomen Very flat, and softer than in other bees. Leg  Hind basitarsus is thinner than the hind tibia, and also nearly as long as it (Figure 69). Wing  The second submarginal cell is shorter than the first. And the first submarginal crossvein makes a right angle with the bottom vein, and ends close to the first recurrent vein (Figure 67).......................................................... Hesperapis /

b. Abdomen More robust, rounded, and not so soft.

Leg  Hind basitarsus is the same width as the hind tibia, but shorter than it (Figure 70). Wing  The second submarginal cell is as long as or longer than the first. And the first submarginal crossvein is strongly angled, so that its junction is usually far away from the first recurrent vein (Figure 66). .................................... Macropis /

Figure 69

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Figure 70

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43 a. Leg Basitibial plate large, with a central area that is velvety (Figure 71). Abdomen  On T1 there is a carina that runs the length, separating the dorsal and anterior portions (Figure 72). ..................................................................... Exomalopsis /

b. Leg Basitibial plate small, without a central area that is velvety (Figure 73).

Abdomen  On T1 there is no carina that runs the length, separating the dorsal and anterior portions (Figure 74). .................................................................. Anthophorula /

Figure 71

Figure 72

Figure 73

Figure 74

Figure 75

Figure 76

44 a. Head Genal area is thickened, as is the vertex, so that the head appears thick (Figure 75). Abdomen  On the sternal segments, dense tufts of hair (scopa) occur laterally on S2–S5, and then continue up the sides of the tergites. First tergal segment is indented, so that its shape is V-like from above (Figure 76); this character is not always a strong one. ................................................................ Dieunomia /

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b. Head The head may be thick or thin.

Abdomen  First tergal segment is gently to strongly concave, but not deeply notched. No tufts of dense scopal hair laterally on S2–S5. ................................... ▸ Go to 45

45 a. Legs Arolia absent (Figure 77)............................................................................... ▸ Go to 46

b. Legs Arolia present (Figure 78). ............................................................................. ▸ Go to 47

Figure 77

Figure 78

46 a. Size Extremely large black bee with extensive and bristly scopal hairs, restricted to tibia (Figure 79). Wing  Smoky, and marginal cell long and thin, and extends to long point that curves gently from the wing margin. Base of marginal cell extends over top of prestigma; there is no stigma. Second submarginal cell notably narrows as it approaches the marginal cell. Abdomen  Few hairs are seen, so that the polished tergal segments are easily visible. No yellow hairs on females of this bee. .................................................... Xylocopa /

b. Size Small to large bee of various coloration.

Wing  On the wing, the marginal cell is not shaped as above, and a stigma is present (Figure 80). Abdomen  The abdomen is hairy, with either hair bands or hair all over. ............... Centris / Note: The rare Ptilothrix will also key out here; it is not found in western states, except parts of Texas.

Figure 79

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Figure 80

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47 a. Wing Outer vein of first submarginal cell exactly meets first recurrent vein (forming a +) (Figure 81)........................................................................................................... Caupolicana /

b. Wing Outer vein of first submarginal cell does not meet first recurrent vein...... ▸ Go to 48

1 1

Figure 81

Figure 82

2

3

2 4

4

3

Figure 83

48 a. Body shape: Petite, not bulky; andreniform with abdomen tapering at either end. Tongue: Short-tongued, with all labial palpi of the same length, and glossa pointed (Figure 82)..................................................................................................... Melitta /

b. Body shape  Bulky, chunky, robust, or hairy bee; anthophoriform or euceriform.

Tongue  Long-tongued, with first and second labial palpi much longer than the third and fourth (Figure 83)............................................................................... ▸ Go to 49

49 a. Wing  Inside cells of wing are bare, with no erect hairs. Stigma shorter, not much different from the prestigma (Figure 84)........................... Anthophorini / ▸ Go to 50

b. Wing Inside cells of wing are covered with small erect hairs; these are best viewed across the plane of the wing, and the hair bases are often the most visible part. Stigma usually larger (less so in Eucera), significantly bigger than the prestigma (Figure 85). .......................................................................................

Figure 84

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▸ Go to 51

Figure 85

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50 a. Wing The submarginal cells cover more than half its length. The first recurrent vein ends very near middle of the second submarginal cell (Figure 84)............................................................................................................ Anthophora /

b. Wing The first recurrent vein ends near the junction of the second and third submarginal cells (Figure 86).............................................................................. Habropoda /

Figure 86 Figure 87

Figure 88

51 a. Head When viewed from front, the vertex rounds gently, so that the ocelli are all below the margin that is the top of the head (Figure 87)............ Emphorini / ▸ Go to 52

b. Head When viewed from front, the vertex is concave to flat, so that the ocelli, and even the compound eyes, stand out from the margin that is the top of the head (Figure 88).................................................................................................. ▸ Go to 53

52 a. Head No carina next to inner eye margin (Figure 89)...........................................Diadasia / b. Wing A carina runs the length of the inner eye margin (Figure 90)..................Ancyloscelis / Note: Ancyloscelis has a rounded head (see couplet 51), but it is not as well developed as in Diadasia and may not be as distinctive. See the genus description for other characteristics.

Figure 89

Figure 90

53 a. Wing  Marginal cell not short, but ending abruptly with a downward angle (Figure 68)..........................................................................................Exomalopsini ▸ Go to 54

b. Wing Marginal cell tapering to a rounded point..................................................... ▸ Go to 55

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54 a. Leg Basitibial plate large, with a central area that is velvety (Figure 71). Abdomen  On T1 there is a carina that runs the length, separating the dorsal and anterior portions (Figure 72)........................................................................Exomalopsis /

b. Leg Basitibial plate small, without a central area that is velvety (Figure 73).

Abdomen  On T1 there is no carina that runs the length, separating the dorsal and anterior portions (Figure 74)..................................................................... Anthophorula /

55 a. Thorax Tegula narrowed at the front end (anterior) to a point (Figure 91). The hair may need to be scraped from tegula for this to be clearly seen.............. ▸ Go to 56

b. Thorax Tegula round, not narrowed at all at the anterior end................................ ▸ Go to 57 Figure 92

Figure 91

Figure 93

56 a. Head Mandible ends in a simple point. Last antennal segment much less than twice as long as wide (Figure 92).................................................................. Melissodes /

b. Head Mandible deeply notched, so that it appears bidentate. Last antennal segment about twice as long as it is wide (Figure 93)........................................ Martinapis /

57 a. Head Clypeus more or less flat, protruding only slightly from face. Abdomen  On T2, at least some of the hairs are branched at the base, and spoon-shaped at the tip (Figure 94)...........................................................................Svastra /

b. Head Clypeus protrudes significantly from face (Figure 95).

Abdomen  Notable hair bands, but with hairs shaped as those described above ........ Eucera / Note: There are several genera not included in this book in the Eucerini that will key to this place, including Gaesischia, Melissoptila, Simanthedon, and Syntrichalonia. All are rare and occur primarily in Mexico, and just across the border in the U.S. See the Apidae chapter for more details.

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Figure 94

Figure 95

Figure 96

58 a. Wing One submarginal cell. Marginal cell is a tiny circle (Figure 96). Size  Minuscule, covered in appressed ghostly white hairs................................... Neolarra ?

b. Wing Two or 3 submarginal cells. Marginal cell is elongated, even slightly.

Size  Minuscule to large. ......................................................................................... ▸ Go to 59

59 a. Head The antennal sockets are on the lower half of the face; below the midpoint of the inner margin of the compound eyes, and only about the width of one antennal socket above the top (base) of the clypeus (Figure 58). ................................................................... Rophitinae ? ▸ Go to 60

b. Head The antennal sockets are higher on the face, occurring above or at the midpoint of the inner margin of the compound eyes, and appearing well above the top of the clypeus. .................................................................................

▸ Go to 64

60 a. Wing Two submarginal cells....................................................................................▸ Go to 61

b. Wing Three submarginal cells...............................................................................

▸ Go to 62

61 a. Head Clypeus protrudes notably from face, when viewed in profile. Wing  The distance from the end of the stigma to the end of the marginal cell is usually the same as the distance from the end of the marginal cell to the tip of the wing (Figure 60). .................................................................................... Dufourea ?

b. Head Clypeus does not protrude from head notably when viewed in profile.

Wing  The distance from the end of the stigma to the end of the marginal cell is less than distance from the apex of marginal cell to the wing tip (Figure 61). ....................................................................................................... Micralictoides ? Note: The rare Sphecodosoma beameri will also key out here; it is not described in this book. In that species the head and thorax are heavily pitted; Micralictoides has weaker punctation.

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A KEY TO BEE GENERA IN WESTERN NORTH AMERICA  365

62 a. Leg Outer hind tibial spur and mid tibial spur with coarse teeth (Figure 62). .................................................................................................................................Xeralictus ?

b. Leg Outer hind tibial spur with minute teeth......................................................... ▸ Go to 63

63 a. Thorax The dorsal portion of the propodeum is short, about 2/3 as long as the scutellum (Figure 63).............................................................................Protodufourea ?

b. Thorax The dorsal portion of the propodeum is longer, about the same length as the scutellum (Figure 64)............................................................... Conanthalictus ? Note: The rare Sphecodosoma dicksoni will also key out here; it is not described in this book. In that species the thorax is smooth and shining between pits; Conanthalictus has a duller surface.

64 a. Wing Three submarginal cells................................................................................ ▸ Go to 65

b. Wing Two submarginal cells................................................................................. ▸ Go to 102

65 a. Wing Basal vein strongly arced, rather than running as a straight line to the first submarginal cell (Figure 45)..................................................................................... ▸ Go to 66

b. Wing Basal vein straight, not strongly arcing in toward the wing base before meeting the first submarginal cell. ......................................................................... ▸ Go to 72

66 a. Head Usually with a yellow spot on the clypeus, often shaped like a top hat. Tongue is long (Figure 97). Wing  Second submarginal cell is triangular, distinctly narrowing at the end nearest the wing margin. Abdomen  Each tergal segment is slightly constricted, so that the abdomen appears to have wavy edges (Figure 47).................................................................. Ceratina ?

b. Head Never with yellow on the clypeus. Tongue is short, tapering to a point.

Wing  Second submarginal cell is more or less square. Abdomen  Tergal segments not constricted at apices, so each segment appears to flow smoothly into the next one............................................................ ▸ Go to 67

Figure 97

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67 a. Thorax Bright polished green. Abdomen  Green, or yellow-and-brown striped (Figure 98)..................................

▸ Go to 68

b. Thorax May be lightly metallic green or coppery, but not brilliantly so; more commonly brown or black.

Abdomen  Brown, red, metallic green, or black. ...................................................

▸ Go to 70

Figure 98

68 a. Head Inner margin of compound eye without distinct notch, runs smoothly from bottom of face to the top. Clypeus with yellow stripe at apex (Figure 99). Thorax  The posterior surface of the propodeum is completely outlined by a strong carina (Figure 48). Abdomen  Yellow-and-brown striped. ............................................................. Agapostemon ?

b. Head Inner margin of compound eye with distinct notch, usually just above level of antennal sockets. Clypeus completely green (Figure 100).

Thorax  The propodeum gently curves to its lateral and dorsal surfaces, with no clear carina completely encircling the posterior surface (Figure 43). Abdomen  Green........................................................................... Augochlorini ? ▸ Go to 69

Figure 99

Figure 100

69 a. Thorax Tegula dented in on the interior side, so that the overall shape of the tegula is a C shape; not symmetric. Tegula metallic green, at least in part (Figure 52). Legs  Hind tibia all green (Figure 101). Abdomen  Apex of T1 and T2 lined with a row of short, stout, unbranched bristles (Figure 53).......................................................................................... Augochloropsis ?

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b. Thorax Tegula oval in shape, with no indentations on the interior side. Tegula brown.

Legs  Hind tibia yellow, black, or red brown, but not all green (Figure 102). Abdomen  There is no row of stout bristles on either T1 or T2...................... Augochlorella ? Note: Augochlora will also key out here based on these characters; it is a common genus in the East, but very rare in the West. It can be distinguished from Augochlorella by the presence of a strong lobe or flap on the paraocular area that extends down over the lateral edges of the clypeus, and the marginal cell, which is cut off at its apex in Augochlora.

Figure 101

Figure 102

70 a. Head Much wider than long. Abdomen  Usually deep blood red. Thorax  Pits are wide and deep, so that the integument appears thickened (Figure 103)............................................................................................................. Sphecodes ? Note: A few Sphecodes have 2 submarginal cells. Male Sphecodes thus comes out twice in the key.

b. Head As wide as, or longer than wide.

Abdomen  Occasionally red, but usually black, brown, or lightly metallic green. Thorax  Pitted, but not so that the integument appears substantially thickened................................................................................................................... ▸ Go to 71

Figure 103

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Figure 104

71 a. Head The lower half of the clypeus is frequently yellow (Figure 104). Abdomen  T1–T4 with strong, clearly evident bands of hair running across the apex of each. In worn specimens, this may be most visible laterally on each tergal segment (Figure 55). Wing  The veins separating the first, second, and third submarginal cells from each other are always dark and strongly presented........................................Halictus ?

b. Head The lower half of the clypeus is not yellow.

Abdomen  T1–T4 either without any hair bands at all or if hair bands are present, they are at the base of each tergal segment, emerging from under the apical margin of the tergal segment before. This is best viewed at the lateral margins, rather than in the center (Figure 56). Wing  The veins separating the first, second, and third submarginal cells from each other may be weak (Figure 57).........................................................Lasioglossum ? Note: A few Lasioglossum have 2 submarginal cells. Male Lasioglossum thus comes out twice in the key.

72 a. Head Two subantennal sutures run from each of the antennal sockets to the top of the clypeus (this may be hard to see through thick hair, especially in larger species) (Figure 26)............................................ Andrenidae ? ▸ Go to 73

b. Head One subantennal suture runs from each of the antennal sockets to the . top of the clypeus......................................................................................................▸ Go to 77

73 a. Wing Stigma nearly absent. Marginal cell nearly 7 times as long as it is wide (Figure 28)................................................................................................... Protoxaea ?

b. Wing Stigma clearly present. Marginal cell may be long, but not exceedingly narrow........................................................................................................................▸ Go to 74

74 a. Wing Apex of marginal cell truncate, so that the tip of the marginal cell ends abruptly, rather than tapering to a gentle point (Figure 41).............................. Protandrena ? Note: Also in this couplet would fall the rare genus Anthemurgus, which is found some in the Midwest and in the East. It looks like Protandrena except for very short mouthparts. Some Protandrena have 2 submarginal cells, so this genus comes out twice in the key.

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b. Wing Apex of marginal cell tapers to a narrowly rounded point at the edge of the wing margin......................................................................................................... ▸ Go to 75

75 a. Abdomen The anterior surface of T1 is broadly concave (Figure 31)............. Ancylandrena ?

b. Abdomen The anterior surface of T1 has a tiny concavity, but it does not occupy the majority of the face (Figure 32).............................................................. ▸ Go to 76

76 a. Leg Hind basitarsus more than half as long as hind tibia (Figure 33). ................. Andrena ? Note: A few Andrena have 2 submarginal cells. Male Andrena thus come out twice in the key.

b. Leg Hind basitarsus about the same length as the hind tibia (Figure 34)...... Megandrena ?

77 a. Head  Antennae extremely long, extending to the beginning of the abdomen (Figure 105).............................................................................Eucerini ? ▸ Go to 78

b. Head Antennae short to modest, never extending to the beginning of the abdomen.................................................................................................................... ▸ Go to 81

Figure 106 Figure 105

Figure 107

78 a. Thorax Tegula narrowed at the front end (anterior) to a point. The hair

may need to be scraped from tegula for this to be clearly seen (Figure 91).........

▸ Go to 79

b. Thorax Tegula round, not narrowed at all at the anterior end. ............................

▸ Go to 80

79 a. Abdomen T7 with a tooth or strong angle to either side of the center where the pygidial plate is (Figure 106)................................................................. Melissodes ?

b. Abdomen T7 without lateral teeth near the pygidial plate (Figure 107)............. Martinapis ?

80 a. Head With four maxillary palpi (Figure 108). One group of Svastra has five maxillary palpi; this group also has hairs on T2 that are plumose at the base, and spatulate at the ends (Figure 94)...........................Svastra ? (mostly summer)

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1 2 3 4

Figure 108



b. Head With three, five, or six maxillary palpi, but not four. No flattened hairs on T2. ...................................................................................... Eucera ? (mostly spring) Note: There are several genera not included in this book in the Eucerini that will key to this place, including Gaesischia, Melissoptila, Simanthedon, and Syntrichalonia. All are rare and occur primarily in Mexico and just across the border in the U.S. See the Apidae chapter for more details.

81 a. Hair Hair across entire body is flattened, and appressed. In some cases almost scalelike. .....................................................................................................

▸ Go to 82

b. Hair Erect, fluffy hair can be found widely across all parts of the body, especially the thorax. Flattened hairs may occur on the abdomen.........................▸ Go to 85

82 a. Leg Arolia absent (Figure 77). ............................................................................... Zacosmia ?

b. Leg Arolia present (Figure 78). ................................................................................... Go to 83

83 a. Leg The apex of the mid tibial spur is notched or has multiple points, like prongs on a salad fork, on its tip. This is in addition to the fine serrations down the side (Figure 109. ...................................................................................... Ericrocis ? Leg  The apex of the mid tibial spur is pointed, not notched or with more than one point. ................................................................................................................ Note: Hexepeolus, which is not covered in this book, will key out to here. There is only one species in the West (H. rhodogyne), found only in the Southwest, and it is a parasite of Ancylandrena. Hexepeolus has a rust-red abdomen with appressed apical hair bands, unlike Epeolus and Triepeolus below.

▸ Go to 84

Figure 109

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84 a. Abdomen Pygidial plate is gently rounded, but flat when viewed from the side (Figure 110). ........................................................................................................ Epeolus ?

b. Abdomen Pygidial plate is constricted at the middle when viewed from above (Figure 111)................................................................................................... Triepeolus ?

Figure 110

Figure 111

85 a. Abdomen First tergal segment is divided by a deep notch, so that its shape is V-like from above (Figure 76). Tergal segments are brown or black, but not iridescent. Legs  Hind legs enlarged, with tibia and femur often flattened (Figure 112). Head  Genal area is thickened, as is the vertex, so that the head appears thick. The final antennal segment is flattened, and much broader than it is long (Figure 113).................................................................................................... Dieunomia ?

Figure 112 Figure 113

b. Abdomen First tergal segment is gently curved, or strongly concave, but not deeply notched.

Legs  Hind legs not notably enlarged with femur or tibia flattened. Head  Genal area is not greatly thickened, and the final antennal segment is not modified in any way. .........................................................................................

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▸ Go to 86

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86 a. Abdomen Tergal segments are strongly iridescent, almost pearlescent, and often with a margin of ivory as well, and completely lacking punctation or hairs (Figure 65).......................................................................................................... Nomia ?

b. Abdomen Tergal segments black, brown, or hairy, but not strongly iridescent as described above. ..................................................................................................▸ Go to 87

87 a. Wing First recurrent vein meets end of first submarginal cell exactly on, forming a + (Figure 81)........................................................................................................... Caupolicana ?

b. Wing First recurrent vein meets row of submarginal cells somewhere between second and third cell, not at the junction of first submarginal crossvein. ................................................................................................................. ▸ Go to 88

88 a. Leg Arolia absent (Figure 77)................................................................................. ▸ Go to 89

b. Leg Arolia present (Figure 78). ............................................................................... ▸ Go to 90

89 a. Wing Marginal cell long and skinny, at least 6 times as long as it is wide. Stigma missing (Figure 79). Wings are smoky. ................................................................................ Xylocopa ?

b. Wing Marginal cell elongated, but not so that it is 6 times as long as wide. Stigma may be small, but is definitely present. Wings are clear (Figure 80)............Centris ?

90 a. Wing The inner portions of the wing, inside the cells, are bare of all hair, appearing shiny. Outside the wing cells near the wing apex, numerous hair follicles are evident (Figure 84). ...............................................................................▸ Go to 91

b. Wing The inner and outer portions of the wing are equally hairy or covered in follicles; there is no clear distinction (Figure 85)...................................................

▸ Go to 94

91 a. Wing Marginal cell longer than the end of the last submarginal cell (Figure 84). ................................................................................... Anthophorini ? ▸ Go to 92

b. Wing Marginal cell short; ending about where the last submarginal cell ends (Figure 114). ......................................................................................... Melectini ? ▸ Go to 93

Figure 114

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92 a. Wing The submarginal cells cover more than half its length. The first recurrent vein ends very near middle of the second submarginal cell (Figure 84). .......................................................................................................... Anthophora ?

b. Wing The first recurrent vein ends near the junction of the second and third submarginal cells (Figure 86). ............................................................................ Habropoda ?

93 a. Leg Inner fork of tarsal claw on hind leg is pointed, and about the same length as the outer fork—not inflated at its base (Figure 115). ............................... Melecta ?

b. Leg Inner fork of tarsal claw on hind leg (and often mid) is inflated at its base, and pointed at the end (Figure 116)................................................................ Brachymelecta ?

Figure 115

Figure 116

94 a. Wing Second recurrent vein strongly curved at its center, so that it appears sigmoidal (Figure 43).................................................................................................. Colletes ?

b. Wing Second recurrent vein very straight. ...........................................................

▸ Go to 95

95 a. Hair Typically bright yellow hair on head, thorax, and abdomen, with some black, red, or white stripes present on abdomen. Head  Malar space long, usually at least as wide as width of compound eye. Wing  Hind wing missing jugal lobe (Figure 5)........................................................ Bombus ?

b. Hair May be hairy, but hair is not bright yellow, or otherwise as above.

Head  Malar space not as long as the width of the compound eye. Wing  Hind wing with perfectly normal jugal lobe. ................................................ ▸ Go to 96

96 a. Head Compound eyes hairy (Figure 2)......................................................................... Apis ?

b. Head Compound eyes not hairy. ...........................................................................

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▸ Go to 97

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97 a. Leg Hind femur swollen, at least twice as thick as middle femur (Figure 117). ......................................................................................................... Ancyloscelis ?

b. Leg Hind femur may be long or short but is not swollen as described above. ......................................................................................................................

▸ Go to 98

Figure 117

98 a. Integument Body has large patches of deep red, or yellow, mixed with black on the head, thorax, and abdomen. Hair is minimal. ............................................ Nomada ? Note: This is where most Nomada key to; they have 3 submarginal cells. A few have lost the second submarginal crossvein so they appear to have 2 subequal submarginal cells. Those individuals will key out below. Brachynomada will also key to this couplet; this genus is not covered in this book and is very rare.

b. Integument Body may have yellow or red on head or on abdomen but is not predominantly colored so. There is significant hair either in bands, or broadly across the body. ....................................................................................................... ▸ Go to 99

99 a. Wing Marginal cell is long, with rounded tip that ends right on wing margin (Figure 118). ................................................................................................................ Melitta ?

b. Wing Marginal cell is not as above.......................................................................... Go to 100

100 a. Wing Marginal cell rounds to a point that is just off the wing margin

(Figure 119).............................................................................................................. Diadasia ?



b. Wing Marginal cell angles abruptly away from wing margin, with a point well off the edge (Figure 120). ........................................................ Exomalopsini ▸ Go to 101

Figure 118

Figure 119

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Figure 120

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A KEY TO BEE GENERA IN WESTERN NORTH AMERICA  375

101 a. Leg Basitibial plate large, with a central area that is velvety (Figure 71). Abdomen  On T1 there is a carina that runs the length, separating the dorsal and anterior portions (Figure 72). ..................................................................... Exomalopsis ?

b. Leg Basitibial plate small, without a central area that is velvety (Figure 73).

Abdomen  On T1 there is no carina that runs the length, separating the dorsal and anterior portions (Figure 74). .................................................................. Anthophorula ?

102 a. Head Two subantennal sutures run from the clypeus to the antennal

socket (Figure 26)............................................................................Panurginae ? ▸ Go to 103



b. Head Just one subantennal suture runs from the clypeus to the antennal socket....................................................................................................................... ▸ Go to 107

103 a. Wing The marginal cell is often so truncate as to appear as a square. The stigma is enlarged, almost as big as the marginal cell (Figure 35).

Size  Minute: 4–8 mm. ...................................................................... Perditini ? ▸ Go to 104

b. Wing The marginal cell is slightly truncated but is much longer than wide. Cell is angled off wing margin (Figures 38, 39, 41).

Size  Small to medium: 6–10 mm. ......................................................................... ▸ Go to 105

104 a. Wing Stigma slender, not much (if at all) wider than the prestigma

(Figure 36). ............................................................................................................ Macrotera ?



b. Wing Stigma large (Figure 35). ................................................................................. Perdita ?

105 a. Head Anterior tentorial pit is along the outer subantennal suture (Figure 37).

Extensive yellow or ivory markings that include the scape and other antennal segments, and areas next to each compound eye (Figure 121). Eyes, especially of live specimens, appear a light blue.

Wing  Marginal cell rounds gently off wing margin. Not immediately truncated. Stigma is small and often narrow, about the same size as the prestigma (Figure 38).............................................................................................. Calliopsis ?

Figure 121

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376  A KEY TO BEE GENERA IN WESTERN NORTH AMERICA



b. Head Anterior tentorial pit is along the epistomal suture, usually at the junction of the epistomal suture and the outer subantennal suture. There may be some yellow, but markings are not extensive. Eyes are dark gray to black.

Wing  Marginal cell is sharply truncated, as a straight line. Stigma is variable. .................................................................................................................

▸ Go to 106

106 a. Thorax On side of body, pre-episternal groove is missing (Figure 40). Wing  First recurrent vein exactly meets the first transverse cubital (the vein separating the 2 submarginal cells) (Figure 39). Abdomen  T2–T5 are hairy along the margins. .................................................. Panurginus ?

b. Thorax On side of body, pre-episternal groove is visible (Figure 42).

Wing  First recurrent vein meets the middle of the second submarginal cell, not exactly meeting the first transverse cubital (Figure 41). Abdomen  T2–T5 are not hairy along the margins............................................ Protandrena ? Note: This is mostly Protandrena in the subgenus Pseudopanurgus.

107 a. Thorax Metanotum has a central spine that projects out over the propodeum.

May be hidden by hair. Scutum is covered in deep coarse pits (Figure 122)............. Dioxys ?



b. Thorax Metanotum without a central spine. Scutum is variously pitted............ ▸ Go to 108

Figure 122 Figure 123

108 a. Thorax The axillae are developed into spines; they may be long and pointed, or shorter and blunted, but the axillae are never rounded off (Figure 123).

Abdomen  T6 with 4 teeth (Figure 124). ................................................................. Coelioxys ?

b. Thorax The axillae are rounded and in line with the metanotum.

Abdomen  T6 without teeth..................................................................................

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▸ Go to 109

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A KEY TO BEE GENERA IN WESTERN NORTH AMERICA  377

109 a. Hair Hair on thorax is flattened, scalelike appressed hairs. ............................... ▸ Go to 110

b. Hair Hair on thorax may be abundant, or sparse, but it is not flattened appressed hairs....................................................................................................... ▸ Go to 113

110 a. Head Labrum much longer than it is wide (Figure 124). ...................................... ▸ Go to 111 b. Head Labrum much wider than long (Figure 125). ............................................... ▸ Go to 112



Figure 124

Figure 125

Figure 126

Figure 127 Figure 128

111 a. Hair Body with isolated patches of flattened scalelike hairs. Wing  Each of the 2 submarginal cells receives one of the recurrent veins (Figure 126)......................................................................................................... Holcopasites ?

b. Hair Body without isolated patches of flattened scalelike hairs; the flattened hairs are distributed across the body.

Wing  Both of the 2 recurrent veins end at the second submarginal cell (Figure 127)........................................................................................................... Oreopasites ?

112 a. Wing Second submarginal cell, though shorter than first, not reduced to

a sliver (Figure 128). ........................................................................................ Townsendiella ?



b. Wing Second submarginal cell significantly shorter than first; either a tiny sliver of a cell or completely absent (Figure 96). .................................................. Neolarra ?

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378  A KEY TO BEE GENERA IN WESTERN NORTH AMERICA

113 a. Integument Predominantly yellow and red, or yellow and black on head,

thorax, and abdomen (all 3, not just the abdomen, or around the clypeus).

Hair  Minimal.......................................................................................................... ▸ Go to 114

b. Integument May have some yellow, black, or red coloring, but body is mostly dark, and coloring is mostly restricted to clypeus and areas around it, or to leg joints, or to head and abdomen, but not thorax............................................. ▸ Go to 120

114 a. Wing Marginal cell is long and ends in an acute point on the wing margin

(Figure 129)............................................................................................................... Nomada ?



b. Wing Marginal cell is rounded or squared off, not ending as an acute point on the wing margin (Figure 130)....................................................... Anthidiini ? ▸ Go to 115 Figure 129

Figure 130

115 a. Abdomen T7 has teeth, spines, projections, or other modifications along its

apex, or just above......................................................................................................... Stelis ?



b. Abdomen There are no spines or other modifications on T7. ...................................................................................... nonparasitic Anthidiini ? ▸ Go to 116

116 a. Legs No arolium between the claws (Figure 8). Head  Mandible has at least five teeth, usually six or more; many are small (Figure 9).............................................................................................................. Anthidium ?

b. Legs Arolium between the tarsal claws.

Head  Mandible has fewer than five teeth. ............................................................ ▸ Go to 117

117 a. Head On the face, subantennal suture curves strongly outward before connecting to clypeus (Figure 12).

Thorax  Scutellum extends back (posteriorly) over the metanotum and pronotum as a broad shelf (Figure 13)............................................................. Anthidiellum ?

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A KEY TO BEE GENERA IN WESTERN NORTH AMERICA  379



b. Head On the face, the subantennal suture is a straight line between the antennal socket and the top of the clypeus.

Thorax  Scutellum ends before the metanotum and does not overhang the pronotum.......................................................................................................... ▸ Go to 118

118 a. Abdomen T7 has 3 lobes, with the middle lobe larger and longer than those

on the sides (Figure 131)...................................................................................Paranthidium ?



b. Abdomen T7 has no lobes..................................................................................... ▸ Go to 119

Figure 131

Figure 132

Figure 133

119 a. Head Preoccipital carina that separates its vertex and its posterior face is strong, so that the back of the head is not rounded.

Thorax  On the side of the body, the face that wraps from the side of the body around to the front (called the mesopleuron) is sharply angled, so that it looks like the outside corner of a cube (Figure 10). The front (anterior) margin of the scutum drops off quickly, and it bulges up significantly above the pronotal collar (Figure 132)................................................................................ Dianthidium ?

b. Head Preoccipital carina is not strongly carinate, but rounds gently from the vertex to the back of the head.

Thorax  On the side of the body, the mesopleuron is not sharply angled, but rounds gently. The anterior margin of the scutum tapers gently, not sloping steeply at its front (Figure 133)................................................................................ Trachusa ?

120 a. Wings Basal vein slightly arcuate. First submarginal cell about twice as long as second.

Body  Slender and elongated, often very small (5–12 mm)..................................... Hylaeus ?

b. Wings Basal vein straight. First and second submarginal cells about the same length.

Body  More robust and typically larger (9–16 mm)............................................... ▸ Go to 121

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380  A KEY TO BEE GENERA IN WESTERN NORTH AMERICA

121 a. Tongue: Short, with pointed glossa. First two segments of labial palpus short,

about same length as others (Figure 82)........................... Melittidae (in part) ? ▸ Go to 122



b. Tongue Long, with glossa long and tapering. First 2 segments of labial palpus longer than other palpi (Figure 83)........................ Megachilini and Lithurgini ? ▸ Go to 123

122 a. Abdomen Very flat, and softer than in other bees. Leg  Hind basitarsus is thinner than the hind tibia, and also nearly as long as it (Figure 134)..................................................................................................... Hesperapis ?

b. Abdomen More robust, rounded, and not so soft.

Leg  On the leg, the hind basitarsus is the same width as the hind tibia, but shorter than it (Figure 135)...................................................................................... Macropis ?

Figure 134

Figure 135

123 a. Abdomen Pygidial plate present (Figure 136).................................................... Lithurgopsis ?

b. Abdomen Pygidial plate absent.............................................................................▸ Go to 124

Figure 136

124 a. Legs Arolia absent (Figure 16).............................................................................. Megachile ?

b. Legs Arolia present (Figure 17).............................................................Osmiini ? ▸ Go to 125

125 a. Head Clypeus has a long spoonlike projection hanging down the center

(Figure 22)............................................................................................................... Protosmia /



b. Head Clypeus variously formed, but never with an elongate spoonlike projection hanging down in the center...................................................................▸ Go to 126

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A KEY TO BEE GENERA IN WESTERN NORTH AMERICA  381

126 a. Thorax Propodeum is outlined by a carina that is made of a series of large deep pits (Figure 18).

Abdomen  Anterior surface (forward facing) of T1 widely concave, with a strong carina lining the edge (Figure 19)................................................................. Heriades ?

b. Thorax Propodeum does not have a carina made of deep pits outlining it.

Abdomen  Anterior surface of T1 is not concave.................................................... ▸ Go to 127

127 a. Thorax Parapsidal line is reduced to a small dot (Figure 20). Integument  The body is usually metallic....................................................................Osmia ?

b. Thorax Parapsidal line is long, more than three times as long as it is wide (Figure 21).

Integument  The body is seldom metallic.............................................................. ▸ Go to 128

128 a. Thorax Very elongated, so that the portion of the scutum anterior to the

tegulae is as long as the portion posterior to them (Figure 23)..........................Chelostoma ?



b. Thorax Not elongated, the portion of the scutum anterior to the tegula much . less than the portion posterior to the tegula..........................................................▸ Go to 129

129 a. Thorax The plate that makes up the side of the body (the mesepisternum) is

split into 2 faces divided by a carina (Figure 24). The anterior (forward-facing) portion of this plate is shiny and polished, while the lateral (side-facing) portion is punctate............................................................................................ Ashmeadiella ?



b. Thorax The mesepisternum rounds gently from the anterior to the lateral faces, and both are punctate to the same degree (Figure 25)...................................Hoplitis ?

130 a. Wing One submarginal cell; occasionally 2, but if so, then second one

reduced to a sliver.................................................................................................... Neolarra /



b. Wing Two or 3 submarginal cells............................................................................▸ Go to 131

131 a. Wings Three submarginal cells.............................................................................. ▸ Go to 132

b. Wings Two submarginal cells................................................................................ ▸ Go to 138

132 a. Wings Basal vein strongly arcuate (as in Figure 45)............................................. Sphecodes /

b. Wings Basal vein straight, not strongly curved..................................................... ▸ Go to 133

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382  A KEY TO BEE GENERA IN WESTERN NORTH AMERICA

133 a. Leg The apex of the mid tibial spur is notched with maybe two or

more prongs (this is separate from the fine serrations down the side).................Ericrocis /



b. Leg The apex of the mid tibial spur is pointed, not notched or with more than one point......................................................................................................... ▸ Go to 134

134 a. Wing The inner portions of the wing, inside the cells, are bare of all hair,

appearing shiny. Outside the wing cells near the wing apex, numerous hair follicles are evident...................................................................... Melectini / ▸ Go to 135



b. Wing The inner and outer portions of the wing are equally hairy or covered in follicles; there is no clear distinction...................................................................... ▸ Go to 136

135 a. Leg Outer fork of tarsal claw pointed, not inflated at its base (Figure 115)............. Melecta /

b. Leg Outer fork of tarsal claw on hind leg (and often mid) is inflated at its base, like a balloon, and pointed at the end (Figure 116).............................. Brachymelecta /

136 a. Wing Marginal cell sharply pointed, and ending very near the apex of

the wing (Figure 128)................................................................................................ Nomada /



b. Wing Marginal cell rounded, and not ending very near the apex of the wing................................................................................................................... ▸ Go to 137

137 a. Abdomen Pygidial plate is gently rounded, but flat when viewed from the

side. Pseudopygidial area at the tip of the abdomen covered with a short wide band of silvery hairs that obscure the integument (Figure 96)....................... Epeolus /



b. Abdomen Pygidial plate is constricted at the middle when viewed from above. Pseudopygidial area narrower and longer, in most species, covered in thin gold hairs, through which the integument can be seen (Figure 97)............. Triepeolus /

138 a. Thorax Metanotum has a central spine that projects out over the propodeum

(Figure 122). May be hidden by hair. Scutum is covered in deep coarse pits. .......... Dioxys /



b. Thorax Metanotum without a central spine. Scutum is variously pitted............

▸ Go to 139

139 a. Wing Stigma long. Abdomen  Tapering to a very fine point (Figure 137). ............................................ Coelioxys /

b. Wing Stigma short to medium.

Abdomen  Abdomen rounding evenly at its apex................................................. ▸ Go to 140

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A KEY TO BEE GENERA IN WESTERN NORTH AMERICA  383

Figure 137

140 a. Hair Hair on body is flattened, scalelike appressed hairs.................................... ▸ Go to 141

b. Hair Hair on body may be abundant, or sparse, but it is not flattened appressed hairs......................................................................................................

▸ Go to 143

141 a. Head Labrum much longer than it is wide (Figure 124). ..................................... ▸ Go to 142

b. Head Labrum much wider than long (Figure 125). ........................................ Townsendiella /

142 a. Thorax Deeply pitted, with dense large punctations covering entire surface. Wing  Each of the 2 submarginal cells receives one of the recurrent veins (Figure 126)......................................................................................................... Holcopasites /

b. Thorax Pitted, but pits small and shallow, widely separated by smooth integument.

Wing  Both of the 2 recurrent veins end at the second submarginal cell (Figure 127)........................................................................................................... Oreopasites /

143 a. Body Black, slender. Yellow usually appearing on leg joints, pronotal collar,

clypeus and/or areas near inner margin of compound eyes. No yellow on the abdomen. ........................................................................................................... Hylaeus /



b. Body Black, red, or yellow; yellow or red markings appear on the abdomen, and, usually, broadly across the whole body. ....................................................... ▸ Go to 144

144 a. Wing Marginal cell sharply pointed, and ending very near the apex of the

wing (Figure 128)...................................................................................................... Nomada /



b. Wing Marginal cell rounded, and not ending very near the apex of the wing. .......... Stelis /

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384  Apidae

GLOSSARY

ABDOMEN: The last, most posterior, section of a bee. While it actually begins at the

posterior end of the thorax in bees, for identification purposes here, it refers to the bee’s last large body segment. See metasoma. ANDRENIFORM: Having the general body form of an Andrena, with a thin head, round

thorax, and slender oval-shaped abdomen. ANTENNA (ANTENNAE): The two many-segmented appendages that extend outward

from the center of a bee’s face. Used for touch, taste, and smell. ANTENNAL SOCKETS: The holes from which the antennae emerge. ANTERIOR: Situated near the front of the body, or head. ANTERIOR TENTORIAL PIT: A small pit located along the epistomal suture, one on

either side of center. The location of this pit differs between genera. ANTHOPHORIFORM: Having the general body form and habits of an Anthophora, with

a larger head with large eyes, robust thorax, and thick abdomen. Fast-flying. APICAL: Refers to the apex, or end, of a segment—farthest from where the segment

begins. ARCUATE: Curved, as opposed to straight. AROLIUM (AROLIA): On the leg, padlike structure between the tarsal claws. Often

easiest to see on the forelegs. AXILLA (AXILLAE): On the thorax, a rounded or triangular point just posterior and

lateral of the scutum, behind the tegula. May project out from the body and hang over the metanotum. There is one on either side of the scutum. BASAL: Refers to the beginning of a segment. May be written as basad to mean “just

before.” BASAL VEIN: On the forewing, the vein that forms the end of the radial cell and the

beginning of the first marginal cell. BASITARSUS (BASITARSI): On the leg, the enlarged or elongated segment between the

tibia and the tarsal segments; the segment of the tarsal segments nearest the bee’s body. In bees, the basitarsi are often larger than other tarsal segments; in wasps this is usually not the case. Depending on the leg, may be the fore basitarsus, mid basitarsus, or hind basitarsus. BASITIBIAL PLATE: A small plate at the base of the hind tibia; analogous to a human

knee cap. CARINA (CARINAE): A clearly defined, usually very thin, ridge, like the keel on a boat.

Can be as simple as a raised line, and may be more or less strong depending on the bee and the structure.

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GLOSSARY  385

CARINATE: Having a carina. CLEPTOPARASITE: A bee in which the female lays eggs inside the provisioned nest cell

of another bee; in essence the cleptoparasitic larva “steals” pollen that was left for the host bee’s own offspring. Female cleptoparasitic bees do not have scopae. CLYPEUS (CLYPEI): The section of the face below the antennae, outlined by the

epistomal sutures. May be extremely convex or protruding, or relatively flat. The apical margin may be straight, concave when looking straight on, lobed, or convex depending on the species. In males, often colored. COMPOUND EYE: The large eyes on either side of a bee’s head, made up of many

hexagonal facets. CONCAVE: Curving inward; forming a broad indentation. CONVEX: Curved outward; roundly protruding. CORBICULA (CORBICULAE): A large hairless patch on the hind tibiae of bumble bees,

honey bees, and a few other species, and on the sides of the propodeum in Andrena. The hairless patch is surrounded by curved stiff hairs. The structure is used for carrying pollen. COXA (COXAE): The basal-most segment of a bee’s leg, between the thorax and the

trochanter. Depending on the leg, may be the forecoxa, midcoxa, or hind coxa. DISTAL: Relating to the outermost part; away from the center of the body. DORSAL: Relating to the upper side or “back” of an animal. EPISTERNAL GROOVE: On the thorax, a groove on the side (on the mesepisternum)

that runs vertically, originating below the wing bases. The length of the episternal groove varies in many genera and is absent in some. EPISTOMAL SUTURE: On the head, the groove that outlines the edge of clypeus,

running from the edge of the mandible, around the top of the clypeus, and intersected by one or two subantennal sutures. EUCERIFORM: Having the general body form and habits of a Eucerini, often

with longer antennae, a robust thorax, and a thick abdomen. Slimmer than anthophoriform bees, but also fast-flying. FEMUR: On the leg, the third segment of the leg, between the trochanter and the tibia. FIMBRIA (FIMBRIAE): A fringe of hairlike or comblike projections. FIRST RECURRENT VEIN: On the wing, the vein that runs usually just behind the first or

second submarginal cell. It is on the same “row” as the second recurrent vein and the basal vein. Where it meets with the submarginal cells can aid in identification.

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386  GLOSSARY

FLAGELLOMERE: On the head, any segment of the antennae beyond (distal to) the

scape and pedicel. FLAGELLUM (FLAGELLA): The collection of all flagellomeres on the antennae. FORELEG:  The leg closest to the head. FOREWING:  The wing, one on either side of a bee’s body, that is closest to its head,

when the wings are laid flat so that they are parallel to the ground. FOVEA (FOVEAE): A depressed area; in bees this most commonly refers to the

depression beside each compound eye, which may be filled with hair. FRONS: The central area above the antennal sockets and below the ocelli on a bee’s

head. GALEA: On the mouthparts, the bladelike structure, usually elongated. There is one on

each side of the central proboscis. GENA: On the head, the region between the back of the compound eye and the back of

the head. GENERALIST: See polylectic. GENITALIA: On the abdomen, the collective term for the genital structures of a bee.

Usually refers to male structures. GLOSSA (GLOSSAE): The portion of the tongue nestled between the galea, and nearest

the labial palpi. Analogous to the human tongue. In long-tongued bees, the glossa tends to be long and slender. HEAD: The first, most anterior section of a bee’s body, containing the antennae,

mouthparts, and eyes. HIND LEG:  The leg farthest from the head. HIND WING:  The wing, one on each side of a bee’s body, that is closest to its abdomen,

when the wings are laid flat so that they are parallel to the ground. IMPUNCTATE: A region of the integument with no pits, often shiny. INNER ORBITAL MARGINS: On the head, the inner margin of the compound eyes. May

converge, be parallel, be notched, or be raised depending on the genus. INTEGUMENT:  The hardened external layer of a bee; analogous to human skin. May be

roughened, pitted, hairy, or with ridges. JUGAL LOBE: On the wing, the posterior-most lobe of the hind wing, demarcated by a

notch in the distal margin. May be missing in some genera.

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GLOSSARY  387

LABIAL PALPUS (PALPI): On the mouthparts, the jointed, segmented structures adjacent

to the glossa. The number, and relative length, of the palpi may differ between genera, and even families. LABRUM: On the head, the hinged plate that hangs below the clypeus; can fold up or

down in front of the mouthparts. LAMELLATE: Referring to a structure that is thin, platelike, and often translucent. LATERAL: Relating to the sides. LEGS: The three pairs of appendages that hang below a bee’s body; all are attached to

the thorax. LOBE: A rounded protuberance on the body of a bee that seems separated from the

other body parts. MACULATION: A spot of lighter color on an otherwise dark integument. MALAR SPACE: On the head, the area between the basal edge of the compound eye

and the beginning of the mandible. When measuring, it is the shortest distance between the two. MANDIBLE: On the head, large, hardened appendages (paired, one on either side) that

hinge below each compound eye and cross or meet below the center of the clypeus. May contain points at the apical margin that are called “teeth.” The whole structure is analogous to a human jaw. MARGINAL CELL: On the wing, the distal-most cell, past the stigma. It rests on the

anterior margin of the wing. MAXILLARY PALPUS (PALPI): On the mouthparts, the jointed segmented structures

attached to the base of the galea. MEGACHILIFORM: Having the general body form and habits of Megachilidae: head,

thorax, and abdomen all robust, and rounded—not elongate. Abdomen often as wide as thorax. Tendency to hover in front of flowers. MESEPISTERNUM: On the thorax, the segment posterior to the pronotum, making up

the majority of the side of the thorax, with the mesepisternum beginning posterior to it. The midcoxae attach to it ventrally. METANOTUM: On the thorax, the last dorsal segment. Just posterior to the scutellum. METASOMA: The posterior portion of a bee’s body, including the tergal and sternal

segments, and the propodeum. In this book, the word abdomen is used instead of metasoma, and the propodeum is included as part of the thorax. MIDLEGS: The middle set of legs on a bee, between the fore and hind legs. MOUTHPARTS: The mandibles and proboscis of a bee.

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388  GLOSSARY

OCELLUS (OCELLI): Small, simple, round eye used for light detection; bees have three

on top of their head. OLIGOLECTIC: A bee that gathers pollen from a small suite of usually closely related

flowers. Also known as a specialist bee. OMAULUS: On the side of the thorax, the angle separating the forward face and lateral

face of the mesepisternum. OVIPOSITOR: The egg-laying structure on a female bee, modified to sting. PARAOCULAR AREA: On the head, the area between the compound eye and the clypeus. PARAPSIDAL LINE: On the thorax, a line (there are two, one to either side of center) on

the scutum. PEDICEL: On the head, the segment of the antenna between the scape and the

flagellum. PITS: Indentations on the integument of a bee. May be close together or widely spaced,

and of various sizes. The integument between the pits may be shiny or dull, completely separate from the pits. PLUMOSE: Feathered hairs on a bee’s body. POLYLECTIC: A bee that collects pollen from any number of flowering plants, not

appearing to limit itself to some subset of what’s available. Also known as a generalist. POSTERIOR: Toward the hind or rear portion of a bee’s body. PREOCCIPITAL REGION: On the head, the area posterior to the preoccipital ridge that

makes up the back of the head. PREOCCIPITAL RIDGE: On the head, a carina that separates the vertex from the posterior

portion. PREPYGIDIAL FIMBRIA (FIMBRIAE): A brush of dense hairs on the apex margin of T5 in

females. Not present in all females. PRESTIGMA: On the wing, the dark, usually very small area adjacent to the stigma, on

the side closest to the body. Its size varies between genera. PRONOTAL LOBE: On the thorax, a lobe on the posterior edge of the pronotum, toward

the dorsal end. PRONOTUM: The anterior-most segment of the thorax, just behind the head. It is

collarlike and extends from the dorsal surface down each side toward the forelegs. PROPODEAL ENCLOSURE: On the thorax, the posterior face of the propodeum that is

often concave; it might be surrounded by a carina, or modified hairs.

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GLOSSARY  389

PROPODEAL PIT: On the thorax, at the center of the propodeal enclosure, ventral to

where the abdomen joins the thorax, there is a deep pit that may be rounded or elongated depending on the species. PROPODEUM: On the thorax, the last segment; includes both a dorsal and posterior

face. This segment is technically the first segment of the abdomen. PUBESCENCE: Hair on a bee’s body. May be short or long, fine or thick. PUNCTATION: The small pits often seen on a bee’s body. PYGIDIAL FIMBRIA: On the thorax, dense hairs on each side of the pygidial plate on T6;

only in species that have a pygidial plate. PYGIDIAL PLATE: On the abdomen, the flat plate found centrally on T6 of females and

T7 on males. May be surrounded by a ridge and may extend beyond the end of the tergal segment on which it occurs. Not present in all bees. SCAPE: The elongated very first segment of the antennae, emerging from the antennal

socket. SCOPA (SCOPAE): The long, thick, often plumose hairs on female bees used for

collecting pollen. Usually on the hind legs, or on the ventral side of the abdomen. SCROBAL GROOVE: On the thorax, a horizontal groove on the mesepisternum that

intersects the episternal groove, below the tegula. SCUTELLUM: On the thorax, the segment (plate) directly posterior to the scutum. SCUTUM: On the thorax, the large dorsal plate between the wings and behind the head. SECOND RECURRENT VEIN: On the forewing, the vein that delineates the outer edge of

the second medial cell; occurs just below the outermost submarginal cell. SPATULOPLUMOSE: Hairs that are branched, with the ends of each branch flattened. SPECIALIST: See oligolectic. STERNUM (STERNITES, STERNAL SEGMENTS, STERNA): The plates composing the

underside of the abdomen. Numbered from anterior to posterior as S1 to S8. Sternal segments may have protrusions or tufts of hair running across them. STIGMA: On the forewing, a dark-colored spot on the forewing, just before the

marginal cell. STING: On the abdomen, the modified ovipositor of female bees; used as a defense

mechanism. SUBANTENNAL SUTURE: On the head, a groove (or grooves) that runs from the

antennal socket to the epistomal suture around the clypeus.

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SUBMARGINAL CELLS: On the forewing, the two or three cells that make up the row of

cells below the marginal cell. SUPRACLYPEAL AREA: On the head, the area between and below the antennal sockets

and above the clypeus; below the frons, which occurs above the antennal sockets. TARSAL CLAWS: Two fine points (“claws”) at the apex of the leg in bees, may be cleft or

simple. Used for clasping rough surfaces. TARSUS (TARSI): On the leg, the segments distal to the tibia and basitarsus, usually

small and more or less square. There are usually four segments. TEGULA (TEGULAE): On the thorax, small plates that cover the bases of the forewings.

Shape and color differ depending on species. TERGUM (TERGA, TERGITES, TERGAL SEGMENTS): On the abdomen, the plates

composing the dorsal surface of the abdomen, numbered from anterior to posterior as T1 to T7. The first tergal segment, T1, has both an anterior face and a dorsal face, and it may have a carinate ridge separating the two. Tergal segments may have protrusions or bands of hair running across them. THORAX: The middle body part of a bee, sandwiched between the head and the

abdomen. TIBIA: On the leg, the segment between the femur and the basitarsus. TIBIAL SPINE: On the hind leg, the pointed projection that occurs on the apex of the

tibia. It is not hinged and cannot move. Not all bees possess tibial spines, and they can be very small or blunted. TIBIAL SPUR: On the hind leg, the spine or spines that extend from the distal end of the

tibia. Tibial spurs are hinged and moveable. On the foreleg and midleg there is one tibial spur, and in most bees the hind leg has two tibial spurs. TROCHANTER: On the leg, the segment between the coxa and the femur. TRUNCATE: Describing something that is cut off at the tip, rather than drawn out to a

point. TUBERCLES: Small round or knoblike projections in the integument; can hang from

the apex of the clypeus, or can be pimplelike bumps on the surface of the legs. VANNAL LOBE: On the wing, the lobe of the hind wing, just before the jugal lobe. VENTRAL: Relating to the underneath or bottom of the bee. VERTEX: On the head, the topmost portion of the head. Ocelli are located on the vertex. WINGS:  Structures on the side of an organism’s body responsible for flight. In bees

they are thin, membranous, and translucent. There are two wings on each side of a bee’s body: the forewing and the hind wing.

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GENERAL REFERENCES Bohart, G. E. 1970. The evolution of parasitism among bees. USU Faculty Honor Lectures, Paper 18. 30 pp. Cane, J. H., and Sipes, S. 2006. Floral specialization by bees: analytical methods and a revised lexicon for oligolecty. In N. M. Waser and J. Ollerton (eds.), Plant-pollinator interactions: from specialization to generalization. University of Chicago Press. 99–122. Danforth, B. N., Minckley, R. L., Neff, J. J., and Fawcett, F. 2019. The solitary bees. Princeton University Press. Hurd, P. D., Jr. and Linsley, E. G. 1975. The principal Larrea bees of the southwestern United States (Hymenoptera: Apoidea). Smithsonian Contributions to Zoology 193: 1–74. Krombein, K. V. 1967. Trap-nesting wasps and bees: life histories, nests, and associates. Smithsonian Press, Washington, D.C. 570 pp. Linsley, E. G. 1958. The ecology of solitary bees. Hilgardia 27(19): 543–599. Michener, C. D. 2000. The bees of the world. Johns Hopkins University Press. Michener, C. D., McGinley, R. J., and Danforth, B. N. 1994. The bee genera of North and Central America. Smithsonian Institution Press, Washington, D.C. 209 pp. Mitchell, T. B. 1960. Bees of the eastern United States, 2 vols. North Carolina Agricultural Experiment Station, Raleigh. 557 pp. Stephen, W. P., Bohart, G. E., and Torchio, P. F. 1969. The biology and external morphology of bees with a synopsis of the genera of north-western America. Northwestern Agricultural Experimental Station. Oregon State University, Corvallis. 140 pp. Wilson, J. S., and Carril, O.J.M. 2015. The bees in your backyard: a guide to North America’s bees. Princeton University Press.

HALICTIDAE Blair, B. H., and Cockerell, T.D.A. 1935. The bees of the group Dieunomia. Journal of the New York Entomological Society 43: 201–214. Bohart, G. E. 1947. New North American bees of the genus Dufourea (Apoidea—Halictidae) part I. Annals of the Entomological Society of America 40: 692–704. Bohart, G. E. 1948. New North American bees of the genus Dufourea (Apoidea—Halictidae) part II. Annals of the Entomological Society of America 41: 119–136. Bohart, G. E. 1949. New North American bees of the genus Dufourea (Apoidea—Halictidae) part III. Annals of the Entomological Society of America 42: 55–62. Bohart, G. E., and Griswold, T. L. 1987. A revision of the dufoureine genus Micralictoides Timberlake (Hymenoptera: Halictidae). Pan-Pacific Entomologist 63: 178–193. Cockerell, T.D.A. 1910. The North American bees of the genus Nomia. Proceedings of the United States National Museum 38 (1745): 289–298. Dumesh, S., and Sheffield, C. S. 2012. Bees of the genus Dufourea Lepeletier (Hymenoptera: Halictidae: Rophitinae) of Canada. Canadian Journal of Arthropod Identification 20: 1–36. Gardner, J., and Gibbs, J. 2020. The ‘red-tailed’ Lasioglossum (Dialictus) (Hymenoptera: Halictidae) of the western Nearctic. European Journal of Taxonomy 725: 1–242. Gibbs, J. 2010. Revision of the metallic species of Lasioglossum (Dialictus) in Canada (Hymenoptera, Halictidae, Halictini). Zootaxa 2591: 1–382.

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Gibbs, J. 2011. Revision of the metallic Lasioglossum (Dialictus) of eastern North America (Hymenoptera: Halictidae: Halictini). Zootaxa 3073: 1–216. Ginsberg, H. S. 1984. Foraging behavior of the bees Halictus ligatus (Hymenoptera: Halictidae) and Ceratina calcarata (Hymenoptera: Anthophoridae): foraging speed on early summer composite flowers. Journal of the New York Entomological Society 92: 162–168. Kerfoot, W. B. 1967. The lunar periodicity of Sphecodogastra texana, a nocturnal bee (Hymenoptera: Halictidae). Animal Behavior 15(4): 479–486. McGinley, R. J. 2003. Studies of Halictinae (Apoidea: Halictidae) II: revision of Sphecodogastra, floral specialists of Onagraceae. Smithsonian Contributions to Zoology 168: 221–425. McGinley, R. J. 1986. Studies of Halictinae (Apoidea: Halictidae) I: revision of New World Lasioglossum Curtis. Smithsonian Contributions to Zoology 429: 1–294. Roberts, R. B. 1973. Bees of northwestern America: Agapostemon. Corvallis Agricultural Experiment Station, Oregon State University. 23 pp. Roberts, R. B. 1973. Bees of northwestern America: Halictus (Hymenoptera: Halictidae). Corvallis Agricultural Experiment Station, Oregon State University. 23 pp. Snelling, R. R., and Stage, G. I. 1995. Systematics and biology of the bee genus Xeralictus (Hymenoptera: Halictidae: Rophitinae). Contributions in Science, Natural History Museum of Los Angeles County 451: 1–17.

COLLETIDAE Almeida, E.A.B. 2008. Colletidae nesting biology (Hymenoptera: Apoidea). Apidologie 39: 16–29. Almeida, E.A.B., and Danforth, B. N. 2009. Phylogeny of colletid bees (Hymenoptera: Colletidae) inferred from four nuclear genes. Molecular Phylogenetics and Evolution 50: 290–309. Michener, C. D., and Deyrup, M. 2004. Caupolicana from Florida (Hymenoptera: Colletidae). Journal of the Kansas Entomological Society 77(4): 774–782. Michener, C. D. 1966. The classification of the Diphaglossinae and North American species of the genus Caupolicana (Hymenoptera, Colletidae). University of Kansas Science Bulletin 46(20): 717–751. Rozen, J. G., Danforth, B. N., Smith, C. S., Decker, B. L., Dorian, N. N., Dority, D., Kilpatrick, S. K., Krichilsky, E., Laws, A. N., and Urban-Mead, K. R. 2019. Early nesting biology of the bee Caupolicana yarrowi (Cresson) (Colletidae: Diphaglossinae) and its cleptoparasite Triepeolus grandis (Friese) (Apidae: Nomadinae). American Museum Novitates 3931: 1–20. Snelling, R. R. 1966. Studies on North American bees of the genus Hylaeus. 1. Distribution of the western species of the subgenus Prosopis with descriptions of new forms (Hymenoptera: Colletidae). Contributions in Science, Los Angeles County Museum 98: 1–18. Snelling, R. R. 1966. Studies on North American bees of the genus Hylaeus. 2. Description of a new subgenus and species (Hymenoptera: Colletidae). Contributions in Science, Los Angeles County Museum 76: 139–144. Snelling, R. R. 1966. Studies on North American bees of the genus Hylaeus. 3. The Nearctic subgenera (Hymenoptera: Colletidae). Bulletin of the Southern California Academy of Sciences 65: 164–175. Snelling, R. R. 1968. Studies on North American bees of the genus Hylaeus. 4. The subgenera Cephalylaeus, Metziella and Hylaeana. Contributions in Science, Los Angeles County Museum 144: 1–6.

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Snelling, R. R. 1970. Studies on North American bees of the genus Hylaeus. 5. The subgenera Hylaeus, s. str. and Paraprosopis (Hymenoptera: Colletidae). Contributions in Science, Los Angeles County Museum 180: 1–59. Stephen, W. 1954. A revision of the bee genus Colletes in America north of Mexico (Hymenoptera, Colletidae). University of Kansas Science Bulletin 36: 149–527.

ANDRENIDAE Barrows, E. M. 1978. Male behavior in Andrena erigeniae (Hymenoptera: Andrenidae) with comparative notes. Journal of the Kansas Entomological Society 51: 798–806. Bouseman, J. K., and LaBerge, W. E. 1978. A revision of the bees of the genus Andrena of the Western Hemisphere. Part IX. Subgenus Melandrena. Transactions of the American Entomological Society 104: 275–389. Cane, J. H., and Buchmann, S. L. 1989. Novel pollen-harvesting behavior by the bee Protandrena mexicanorum (Hymenoptera: Andrenidae). Journal of Insect Behavior 2: 431–436. Danforth, B. N. 1994. Taxonomic review of Calliopsis subgenus Hypomacotera (Hymenoptera: Andrenidae), with special emphasis on the distributions and host plant associations. PanPacific Entomologist 70: 283–300. Danforth, B. N. 1996. Phylogenetic analysis and taxonomic revision of the Perdita subgenera Macrotera, Macroteropsis, Macroterella and Cockerellula (Hymenoptera: Andrenidae). University of Kansas Science Bulletin 55(16): 635–692. Danforth, B. N. 1999. Emergence dynamics and bet hedging in a desert bee Perdita portalis. Proceedings of the Royal Society of London 266: 1985–1994. Davis, L. W., and LaBerge, W. E. 1975. The nest biology of the bee Andrena (Ptilandrena) erigeniae Robertson (Hymenoptera: Andrenidae). Illinois Natural History Survey Biological Notes 95: 1–16. Donovan, B. J. 1977. A revision of North American bees of the subgenus Cnemidandrena (Hymenoptera: Andrenidae). University of California Publications in Entomology. 107 pp. Griswold, T. L., and Parker, F. D. 1988. New Perdita (Perdita) oligoleges on Mentzelia, with notes on related species of the ventralis group (Hymenoptera: Andrenidae). Pan-Pacific Entomologist 64: 43–52. Hurd, P. D., Jr. and Linsley, E. G. 1976. The bee family Oxaeidae with a revision of the North American species (Hymenoptera: Apoidea). Smithsonian Contributions to Zoology 220: 1–75. LaBerge, W. E. 1967. A revision of the bees of the genus Andrena of the Western Hemisphere. Part I. Callandrena (Hymenoptera: Andrenidae). Bulletin of the University of Nebraska State Museum 7: 1–318. LaBerge, W. E. 1969. A revision of the bees of the genus Andrena of the Western Hemisphere. Part II. Plastandrena, Aporandrena, Charitandrena. Transactions of the American Entomological Society 95: 1–47. LaBerge, W. E. 1971. A revision of the bees of the genus Andrena of the Western Hemisphere. Part IV: Scrapteropsis, Xiphandrena, and Rhaphandrena. Transactions of the American Entomological Society 97: 441–520. LaBerge W. E. 1973. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VI. Subgenus Trachandrena. Transactions of the American Entomological Society 99: 235–371. LaBerge W. E. 1977. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VIII. Subgenera Thysandrena, Dasyandrena, Psammandrena, Rhacandrena, Euandrena, Oxyandrena. Transactions of the American Entomological Society 103: 1–143.

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LaBerge, W. E. 1980. A revision of the bees of the genus Andrena of the Western Hemisphere. Part X. Subgenus Andrena. Transactions of the American Entomological Society 106: 395–525. LaBerge, W. E. 1985. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XI. Minor subgenera and subgeneric key. Transactions of the American Entomological Society 111: 441–567. LaBerge, W. E. 1987. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XII. Subgenera Leucandrena, Ptilandrena, Scoliandrena, and Melandrena. Transactions of the American Entomological Society 112: 191–248. LaBerge, W. E. 1989. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XIII. Subgenera Simandrena and Taeniandrena. Transactions of the American Entomological Society 115: 1–56. LaBerge, W. E., and Bouseman, J. K. 1970. A revision of the bees of the genus Andrena of the Western Hemisphere. Part III. Tylandrena. Transactions of the American Entomological Society 96: 543–605. LaBerge, W. E., and Ribble, D. W. 1972. A revision of the bees of the genus Andrena of the Western Hemisphere. Part V. Gonandrena, Geissandrena, Parandrena, Pelicandrena. Transactions of the American Entomological Society 89: 271–358. LaBerge, W. E., and Ribble, D. W. 1975. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VII. Subgenus Euandrena. Transactions of the American Entomological Society 101: 371–446. LaBerge, W. E., and Thorp, R. W. 2005. A revision of the bees of the genus Andrena of the Western Hemisphere. Part VII. Subgenus Onagandrena. Illinois Natural History Survey Bulletin 37: 1–63. LaPlaca Reese, C. S., and Barrows, E. M. 1980. Co-evolution of Claytonia virginica (Portulacaceae) and its main native pollinator, Andrena erigeniae (Andrenidae). Proceedings of the Entomological Society of Ontario 82: 685–694. Linsley, E. G. 1972. Diurnal and seasonal behavior patterns among adults of Protoxaea gloriosa (Hymenoptera, Oxaeidae). American Museum Novitates 2509: 1–26. Michener, C. D. 1935. Some Pacific coast Panurginus (Hymenoptera, Apoidea). Canadian Entomologist 64(12): 275–278. Michener, C. D. 1935. Bees from coastal northern California. Pan-Pacific Entomologist 11(4): 178–184. Norden, B. B., and Scarbrough, A. G. 1979. Nesting biology of Andrena (Larandrena) miserabilis Cresson and description of the prepupa (Hymenoptera: Andrenidae). Brimleyana 2: 141–146. Osgood, E. A. 1989. Biology of Andrena crataegi Robertson (Hymenoptera: Andrenidae), a communally nesting bee. Journal of the New York Entomological Society 97: 56–64. Ribble, D. W. 1967. The monotypic North American subgenus Larandrena of Andrena (Hymenoptera: Apoidea). Bulletin of the University of Nebraska State Museum 6: 27–42. Ribble, D. W. 1968a. Revisions of two subgenera of Andrena: Micrandrena Ashmead and Derandrena, new subgenus (Hymenoptera: Apoidea). Bulletin of the University of Nebraska State Museum 8: 237–394. Ribble, D. W. 1968b. A new subgenus, Belandrena, of the genus Andrena (Hymenoptera: Apoidea). Journal of the Kansas Entomological Society 41: 220–236. Ribble, D. W. 1974. A revision of the bees of the genus Andrena of the Western Hemisphere, subgenus Scaphandrena. Transactions of the American Entomological Society 100: 101–189. Rozen, J. G., Jr. 1967. Review of the biology of panurgine bees, with observations on North American forms (Hymenoptera, Andrenidae). American Museum Novitates 2297: 1–44. Rozen, J. G., Jr. 1989. Life history studies of the “primitive” panurgine bees (Hymenoptera: Andrenidae: Panurginae). American Museum Novitates 2962: 1–27.

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Rozen J. G. 1994. Biologies of the bee genera Ancylandrena (Andrenidae: Andreninae) and Hexepeolus (Apidae: Nomadinae) and phylogenetic relationships of Ancylandrena based on its mature larva (Hymenoptera: Apoidea). American Museum Novitates 3108: 1–19. Thorp, R. W. 1969. Systematics and ecology of bees of the subgenus Diandrena (Hymenoptera: Andrenidae). University of California Publications in Entomology 52: 1–146. Thorp, R. W., and LaBerge, W. E. 2005. A revision of the bees of the genus Andrena of the Western Hemisphere. Part XV. Subgenus Hesperandrena. Illinois Natural History Survey Bulletin 37: 64–93. Timberlake, P. H. 1954. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part I. University of California Publications in Entomology 9: 345–432. Timberlake, P. H. 1956. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part II. University of California Publications in Entomology 11: 247–350. Timberlake, P. H. 1958. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part III. University of California Publications in Entomology 14: 303–410. Timberlake, P. H. 1960. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part IV. University of California Publications in Entomology 17: 1–156. Timberlake, P. H. 1962. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part V. University of California Publications in Entomology 28: 1–124. Timberlake, P. H. 1964. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part VI. University of California Publications in Entomology 28: 125–388. Timberlake, P. H. 1968. A revisional study of the bees of the genus Perdita F. Smith, with special reference to the fauna of the Pacific coast (Hymenoptera, Apoidea). Part VII. University of California Publications in Entomology 49: 1–196. Timberlake, P. H. 1971. Supplementary studies on the systematics of the genus Perdita (Hymenoptera, Andrenidae). University of California Publications in Entomology 66: 1–63. Timberlake, P. H. 1973. Revision of the genus Pseudopanurgus of North America (Hymenoptera, Apoidea). University of California Publications in Entomology 72: 1–58. Timberlake, P. H. 1975. The North American species of Heterosarus Robertson (Hymenoptera, Apoidea). University of California Publications in Entomology 77: 1–56. Timberlake, P. H. 1976. Revision of the North American bees of the genus Protandrena Cockerell (Hymenoptera: Apoidea). Transactions of the American Entomological Society 102: 133–227. Zavortink, T. J. 1972. A new subgenus and species of Megandrena from Nevada, with notes on its foraging and mating behavior. Proceedings of the Entomological Society of Washington 74: 61–75.

MELITTIDAE Cane, J. H., Snelling, R. R., and Kervin, L. J. 1996. A new monolectic coastal bee, Hesperapis oraria Snelling and Stage (Hymenoptera: Melittidae), with a review of desert and Neotropical disjunctives in the southeastern US. Journal of the Kansas Entomological Society 69(4): 38–247.

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MEGACHILIDAE Bosch, J., and Kemp, W. P. 2002. How to manage the blue orchard bee. Sustainable Agriculture Network. 87 pp. Brach, V. 1979. Notes on the biology of Lithurgus gibbosus Smith in Florida (Hymenoptera: Megachilidae). Bulletin of the Southern California Academy of Sciences 77: 144–147. Brooks, R. W., and Griswold, T. L. 1988. A key to the species of Trachusa subgenus Heteranthidium with descriptions of new species from Mexico (Hymenoptera: Megachilidae: Anthidiini). Journal of the Kansas Entomological Society 61(3): 332–346. Bzdyk, E. L. 2012. A revision of the Megachile subgenus Litomegachile Mitchell with an illustrated key and description of a new species (Hymenoptera, Megachilidae, Megachilini). ZooKeys. 221: 31–61. Cane, J. H. 1996. Nesting resins obtained from Larrea pollen host by an oligolectic bee, Trachusa larreae (Cockerell) (Hymenoptera: Megachilidae). Journal of the Kansas Entomological Society 69(1): 99–102. Cane, J. H., Griswold, T., and Parker, F. D. 2007. Substrates and materials used for nesting by North American Osmia bees (Hymenoptera: Apiformes: Megachilidae). Annals of the Entomological Society of America 100(3): 350–358. Cane, J. H., Rust, R. W., and Bohart, G. W. 2009. Resurrecting the bee Osmia aglaia Sandhouse from synonymy (Hymenoptera: Apiformes: Megachilidae). Journal of the Kansas Entomological Society 82(1): 43–45. Eickwort, G. C., Matthews, R. W., and Carpenter, J. 1981. Observations of the nesting behavior of Megachile rubi and M. texana with a discussion of the significance of soil nesting in the evolution of megachilid bees (Hymenoptera: Megachilidae). Journal of the Kansas Entomological Society 54(3): 557–570. Eickwort, G. C. 1980. Two European species of Chelostoma established in New York State (Hymenoptera: Megachilidae). Psyche 87(3–4): 315–323. Evans, H. E. 1993. Observations on the nests of Paranthidium jugatorium perpictum (Cockerell) (Hymenoptera: Megachilidae: Anthidiini). Pan-Pacific Entomologist 69(4): 319–322. Gibbs, J., and Sheffield, S. 2009. Rapid range expansion of the wool-carder bee, Anthidium manicatum (Linnaeus) (Hymenoptera: Megachilidae), in North America. Journal of the Kansas Entomological Society 82(1): 21–29. Gonzalez, V. H., and Griswold, T. L. 2007. A review of the North and Central American Megachile subgenus Argyropile Mitchell (Hymenoptera: Megachilidae). Zootaxa 1461: 1–14.

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  403

INDEX The pages in bold indicate a full description.

argemonis: 106, 110 cerasifolii: 107–108

A

clarkella: 103

Acacia: 295

frigida: 103–104

Agapostemon: 15, 26, 35, 36, 38, 40–46

helianthi: 106–107

crataegi: 105–106, 110

Key couplets: male: 68a, female: 31a

impolita: 108

angelicus: 42, 43

lupinorum: 108–109

coloradensis: 46

milwaukeensis: 102–103

femoratus: 42–43

nasonii: 111

melliventris: 44–45

perarmata: 103, 104

texanus: 41–42

prunorum: 109–110

tyleri: 46

prunorum: 110

virescens: 45–46

sinaloa: 110

Agave: 228, 234 Alfalfa. See Medicago Alkali Bee. See Nomia melanderi Ailanthus: 240 Ambrosia: 195 Ammobatini: 232, 339 Ammobatoidini: 232, 330

vicina: 109 vulpicolor: 107 Andrenidae: 23, 82, 97–146, 147, 330 Key couplets: male: 72a, female: 18a Andreninae: 29, 98, 99, 101, 112 Key couplet: 20a

Anatomy. See Bee Biology

Anthemurgus: 99

Ancylandrena: 31, 98, 99–101, 112

Anthidiellum: 157, 209–211, 216

Key couplets: male: 75a, female: 21a

Key couplets: male 117a, female: 10a

atoposoma: 100

ehrhorni: 211

koebelei: 101

notatum: 210–211

larreae: 99–101 rozeni: 100 timberlakei: 100 Ancyloscelis: 249–251, 292

Anthidiini: 21, 25, 157, 209, 211, 216, 220, 222, 224, 342 Anthidium: 156, 157, 206, 210, 211–216, 225, 342

male: 97a, female: 52a

Key couplets: male: 116a, female: 8a

apiformis: 250

chamelense: 213

melanostoma: 250

maculosum: 212–213

sejunctus: 250–251

manicatum: 156, 213–214

Andrena: 15, 21, 23, 25–27, 31, 35, 40, 47, 66,

mormonum: 214–216

68, 76, 82, 86, 97–99, 101–111, 112, 116,

oblongatum: 213

148, 154, 155, 300, 317–319

parkeri: 213

Key couplets: male: 76a, female: 22a

rodriguezi: 213

angustitarsata: 111

utahense: 215

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404  INDEX

Anthophora: 21, 26, 33, 83, 231, 246, 275–283,

Ashmeadiella: 27, 66, 158, 159–164, 165, 194, 330

284, 292, 295, 303, 332, 333, 335, 336,

Key couplets: male: 129a, female: 17a

337 Key couplets: male: 92a, female: 50a

aridula: 163

(Heliophila): 335

bucconis: 160–161

(Micranthophora): 282, 283

californica: 161

abrupta: 277, 337

cubiceps: 161

affabilis: 281–282

foveata: 164

bomboides: 276–277

gillettei: 161–162

californica: 277–278

holtii: 162

curta: 282

meliloti: 162–163

marginata: 281

occipitalis: 161 opuntiae: 163–164

montana: 389 occidentalis: 277

Asteraceae: 68, 70, 87, 106, 117, 123, 125, 137,

pacifica: 283–284

141, 144, 145, 159, 160, 168, 177, 183–185,

porterae: 282

195, 201, 205, 216, 220, 243, 245, 251, 259, 263, 265, 266, 269, 271, 282

sodalis: 276 terminalis: 275, 278–279

Astragalus: 253

urbana: 279–280

Atoposmia: 158, 159

Anthophorini: 28, 231, 243, 275, 276, 284, 290, 292, 332, 339

Augochlora: 35, 367 Augochlorella: 35, 36–37 Key couplets: male: 69b, female: 32b

Key couplets: male: 91a, female: 49a Anthophorula: 232, 290–292

aurata: 37

Key couplets: male: 101b, female: 43a, 54a

bracteata: 37

compactula: 291–292

neglectula: 37 pomoniella: 37

Apache plume. See Fallugia Apiaceae: 93

Augochlorini: 35, 36–40

Apidae: 13, 31, 68, 83, 97, 152, 230–341

Augochloropsis: 18, 35, 38–40 Key couplets: male: 69a, female: 32a

Apinae: 231, 243, 249, 251, 262, 265, 272, 275, 284, 290, 292, 294, 299, 301, 328, 332,

metallica: 38–40

335, 336

sumptuosa: 40

Apini: 231, 299 Apis: 230, 231, 299–301 Key couplets: male: 96a, female: 4a mellifera: 300–301 cerana: 299

B Bee Biology: Anatomy: 14–21

Apocynum: 152

Cleptoparasites: 13

Arctostaphylos: 182, 283

Definition (what is a bee): 13–14

Argemone: 110, 112

Diet: 12

Asclepias: 271

Generalist: 12

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INDEX  405

Glossary: 384–391

Boraginaceae: 74, 124, 187

Key: 342–383

Brachymelecta: 232, 265, 275, 284, 329, 332, 336–338

Life Cycle: 11 Nesting: 11–12

Key couplets: male: 93b, female: 135b

References: 391–402

californica: 337–338

Sex: 21 Specialist: 12

interrupta: 338 Brachynomada: 233, 290, 292, 318, 374

Berberis: 182

Brachynomadini: 233

Biastini: 232

Buckthorn. See Rhamnus

Blanket flower. See Gaillardia

Buckwheat. See Eriogonum

Blazing star. See Mentzelia

Bumble Bee. See Bombus

Blood Bee. See Sphecodes Blue Orchard Bee. See Osmia lignaria Blueberry: 198

C

Bombini: 231, 301

Cactaceae: 163, 228, 243, 246

Bombus: 24, 25, 30, 33, 231, 234, 276, 284,

Cactus. See Cactaceae

301–317, 332, 343, 373

Cactus Bee. See Diadasia; Lithurgopsis

Key couplets: male: 95a, female: 4b

California poppy. See Eschscholzia

bifarius: 308, 309, 312

Calliopsini: 98, 115

caliginosus: 314, 315

Calliopsis: 25, 27, 32, 98, 115–118, 330, 331,

centralis: 309–311, 312

339–340

cryptarum: 304

Key couplets: male: 105a, female: 25a

fervidus: 314–316, 317

obscurella: 118

flavifrons: 310, 311–312

puellae: 117–118

griseocollis: 304–305, 307

subalpinus: 116–117

huntii: 24, 308, 309, 312–313

Caltrop. See Kallstroemia

mckayi: 304

Calystegia: 246

melanopygus: 308, 312, 313

Campanula: 76

morrisoni: 305, 306–307, 317

Carpenter Bee. See Xylocopa

nevadensis: 317

Cat’s eyes. See Cryptantha

occidentalis: 303–304

Caupolicanini: 83

pensylvanicus: 307, 316–317

Caupolicana: 26, 30, 31, 83–84, 114

(Psithyrus): 302

Key couplets: male: 87a, female: 47a

rufocinctus: 307–308

yarrowi: 84

sonorous. See Bombus pensylvanicus

ocellata: 84

sylvicola: 308, 312, 313

Ceanothus: 122, 139

terricola: 304

Cellophane Bee. See Colletes

vancouverensis: 308–309

Cemolobus. See Eucera

vandykei: 304, 314, 315

Centaurea: 227

vosnesenskii: 304, 313–314, 315

Centridini: 231, 294

02 CBoWNA pp230-416.indd 405

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406  INDEX

Centris: 26, 30, 231, 234, 294–299, 328, 329 Key couplets: male: 89b, female: 46a cockerelli: 295–296 pallida: 296–297 rhodopus: 296, 298–299 Ceratina: 15, 31, 32, 231, 238–242

novomexicanus: 192 octodentatus: 191–192 pratti: 192 rufitarsis: 192–193 Colletes: 29, 31, 47, 66, 71, 82, 85–90, 102, 148, 154, 300, 317, 322–324 Key couplets: male: 94a, female: 27a

Key couplets: male: 66a, female: 29a

birkmanni: 89

acantha: 240, 241

bryanti: 89

apacheorum: 241

daleae: 90

hurdi: 241

fulgidus: 88

nanula: 240, 241–242

lutzi: 86

neomexicana: 242

phaceliae: 86–87

pacifica: 242

salicicola: 89–90

punctigena: 242

simulans: 87–88

shinnersi: 242 Cercidium: 295 Chamaesarachae: 134 Chamaesyce: 133 Chelostoma: 17, 158, 159, 165–167, 168, 194 Key couplets: male: 128a, female: 16a

armatus: 88 nevadensis: 88 simulans: 88 slevini: 88–89 Colletidae: 82–96, 147 Colletinae: 82, 85 Conanthalictus: 31, 36, 74–75

bernardinum: 167

Key couplets: male: 63a, female 38a

californicum: 165–166

(Conanthalictus): 74

cockerelli: 167

(Phaceliapis): 74

minutum: 167

bakeri: 74–75

phaceliae: 167

wilmattae: 75

Chimney Bee. See Anthophora; Diadasia

Convolvulaceae: 243, 246, 247, 249

Cholla. See Cylindropuntia

Convolvulus: 246

Chrysothamnus: 125, 140, 286

Cornus: 103

Cirsium: 195

Cottonwood. See Populus

Clarkia: 150, 247

Creosote bush. See Larrea tridentata

Cleome: 130

Crownbeard. See Verbesina

Cleptoparasites. See Bee Biology

Cryptantha: 138, 288

Coelioxys: 29, 158, 168, 189–193, 194, 206,

Cuckoo Bee. See Brachymelecta; Coelioxys;

224, Key couplets: male: 108a, female: 139a alternatus: 193

Dioxys; Epeolini; Holcopasites; Melecta; Neolarra; Nomada; Oreopasites; Sphecodes; Stelis; Townsendiella; Zacosmia

bisoncornuus: 191

Cucurbita: 256, 257

edita: 190–191

Cylindropuntia: 228, 243

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INDEX  407

D

Diphaglossinae: 83

Dalea: 149

Dufourea: 34, 36, 74, 75–78, 79, 91

Dogwood. See Cornus

Dasypodainae: 147, 148

Key couplets: male: 61a, female 36a

Desert dandelion. See Malacothrix

dilatipes: 76

Diadasia: 13, 186, 231, 243–249, 292

marginata: 77

Key couplets: male 100a, female: 52a

maura: 76–77

angusticeps: 247

mulleri: 77

australis: 243–244

trochantera: 77, 78

bituberculata: 246–247 diminuta: 248–249 enavata: 245–246

E

lutzi: 249

Echinocactus: 228

opuntiae: 245, 246

Elderberry. See Sambucus

rinconis: 245, 246

Emphorini: 231, 243, 249, 275, 292

sphaeralcearum: 249 vallicola: 246 Dialictus: 47, 48, 55, 56–61, 79, 123, 239 Dianthidium: 157, 210, 216–220, 221, 225 Key couplets: male 119a, female: 10b

Key couplets: female: 51a Epeolini: 233, 322, 325, 328 Epeoloides: 152, 232 Epeolus: 85, 233, 265, 322–325, 326 Key couplets: male: 84a, female: 137a

curvatum: 216–217

americanus: 324

platyurum: 219

asperatus: 324

pudicum: 218–219 ulkei: 219 xerophilum: 218

banksi: 325 canadensis: 323 compactus: 322–323

Diascia: 147

ferrarii: 323

Diet. See Bee Biology

mesillae: 323–324

Dieunomia: 27, 30, 34, 35, 68–71, 327 Key couplets: male: 85a, female 44a heteropoda: 68–69. 327 nevadensis: 69–70 triangulifera: 70 Digger Bee. See Anthophorini Dioxyini: 158, 206 Dioxys: 27, 158, 170, 188, 190, 206–209, 211 Key couplets: male: 107a, female 138a pacificus: 207 pomonae: 207–208 productus: 208–209

02 CBoWNA pp230-416.indd 407

minimus: 324–325 olympiellus: 325 Ericameria: 57, 125, 140, 286 Ericaceae: 182 Ericrocidini: 231 Ericrocis: 231, 294, 328–330 Key couplets: male: 83a, female: 133a lata: 329–330 pintada: 330 Erigeron: 195 Eriogonum: 96, 135, 136 Eschscholzia: 79, 138

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408  INDEX

Eucera: 21, 30, 232, 251–261, 265, 272, 273,

solani: 293–294

285, 327, 361

solidaginis: 294

Key couplets: male: 80a, female: 57a (Cemolobus): 232, 251 (Peponapis): 232, 251, 252 (Synhalonia): 251, 252

F Fabaceae: 71, 73, 84, 89, 99, 108, 114, 156, 183,

(Syntrichalonia): 232, 251

187, 201, 205, 253, 263, 268, 269, 295,

(Tetraloniella): 232

296, 298

(Xenoglossa): 232, 251, 252

Fairy Bee. See Macrotera; Perdita

(Xenoglossodes): 232, 251, 252

Fallugia: 131

acerba: 256

Ferocactus: 272, 273

angustior: 253, 258–259

Figwort. See Plantaginaceae

atriventris: 254

Florilegus: 232

cordleyi: 253

Furrow Bees. See Halictinae

edwardsii: 252–253 eriocarpi: 259–260 frater: 253–254

G

fulvitarsis: 254–255

Gaillardia: 139

kansensis: 258

Gaesischia: 232, 363, 370

lippiae: 261

Geranium: 152

patricia: 259

Globe mallow. See Sphaeralcea

pruinosa: 256–257

Goldenrod. See Solidago

spissa: 261

Goldenweed. See Isocoma

strenua: 257–258

Green Metallic Sweat Bee. See Agapostemon

wilmattae: 260

Green Sweat Bees. See Augochlorini

Eucerini: 28, 83, 232, 243, 251, 252, 262, 265, 272, 276, 325, 326, 332, 363, 370, 385 Key couplets: male: 77a

Greenthread. See Thelesperma Grindelia: 125, 144 Gutierrezia: 125

Euglossa: 232 Euglossini: 232 Euphorbia: 133 European Honey Bee. See Apis mellifera European Wool-carder Bee. See Anthidium manicatum

H Habropoda: 26, 83, 231, 251, 275, 284–290, 332, 336 Key couplets: male: 92b, female: 50b

Evening Bee. See Hesperapis

Cineraria: 289

Evening Primrose. See Oenothera

dammersi: 286

Exomalopsini: 232

depressa: 285–286

Exomalopsis: 232, 250, 292–294

excellens: 284, 286–287

(Stilbomalopsis): 294

miserabilis: 286

auropilosa: 293

morrisoni: 288–289

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INDEX  409

pallida: 285, 289–290 Halictidae: 34–81, 91

rozeni: 331 Hoplitis: 20, 26, 158, 159, 165, 168, 170–176,

Halictus: 14, 16, 18, 19, 28, 35, 40, 41, 46–54, 66,

177 Key couplets: male: 129b, female: 17b

67, 76, 86, 91, 116, 148, 154, 317, 318, 319 Key couplets: male: 71a, female 33a

albifrons: 171–172

confusus: 47–49, 54

biscutellae: 172–173

farinosus: 49–50

fulgida: 173–174

ligatus: 50–52

hypocrita: 173

parallelus: 52, 53

paroselae: 173

rubicundus: 49, 52–53 tripartius: 49, 53–55 Helianthus: 68, 106, 125, 137, 144, 145, 160,

producta: 174–175 Hylaeinae: 82, 90 Hylaeus: 12, 31, 32, 82, 90–96, 121, 123, 142,

195, 202, 245, 266, 267, 272, 274

165, 239

Heriades: 158, 159, 165, 168–169, 170, 188, 194

Key couplets: male: 120a, female: 143a

Key couplets: male: 126a, female: 13a

annulatus: 94

cressoni: 168–169

asininus: 95

micheneri: 169

basalis: 95–96

variolosa: 169

bisinuatus: 92

Hesperapis: 29, 80, 147, 148–151, 152, 154,

coloradensis: 96 leptocephalus: 91–92

320–321 Key couplets: male: 122a, female: 42a

megalotis: 94–95

fuchsi:151

mesillae: 91, 93–94

larreae: 148–149

nunenmacheri: 96

laticeps: 149–150

polifolii: 96

laticeps: 150

rudbeckiae: 94

rufiventris: 150

saniculae: 94 wootoni: 96

nitidula: 151 pellucida: 151 regularis: 150–151 semirudis: 151

I

timberlakei: 149

Ipomoea: 249, 250

wilmattae: 151

Isocoma: 140

Heteroperdita: 124, 125 Heterosarus: 142. See also Pseudopanurgus Hexepeolini: 233 Hexepeolus: 99, 233

K Kallstroemia: 114, 142

Holcopasites: 27, 116, 121, 141, 232, 330–331 Key couplets: male: 111a, female: 142a arizonicus: 331 insoletus: 331

02 CBoWNA pp230-416.indd 409

L Lamiaceae: 156, 189

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410  INDEX

Larrea tridentata: 57, 73, 89, 99, 100, 112, 114, 148, 172, 225, 298, Lasioglossum: 26, 27, 28, 30, 32, 35, 47, 48, 55–66, 74, 79, 123, 239, 317,

Long-horned Bee. See Eucerini Loosestrife. See Lysimachia Lupinus: 100 Lysimachia: 151, 152

Key couplets: male: 71b, female 33b (Dialictus): 55, 56–61 (Lasioglossum): 55, 61–64 (Hemihalictus): 55, 65–66

M Macropis: 32, 147, 151–154, 155

(Sphecodogastra): 55, 64–65

Key couplets: male: 122b, female: 42b

albipenne: 57

ciliata: 153, 154

albohirtum: 58

nuda: 152–154

anhypops: 61–63

patellata: 153, 154

coriaceum: 62

steironematis: 153, 154

cressonii: 56–57

Macrotera: 27, 98, 118–121

hudsoniellum: 57

Key couplets: male: 104a, female: 24a

imitatum: 58

arcuata: 118–119

kunzei: 61

echinocacti: 119

microlepoides: 58

latior: 119–120

noctivaga: 65

portalis: 120–121

oceanicum: 57

Mahonia: 182

pruinosum: 59

Malacothrix: 117

pulveris: 65–66

Malus: 178

semicaeruleum: 60

Malvaceae: 243, 248, 249

semibrunneum: 61

Mallow Bee. See Diadasia

sisymbrii: 63

Martinapis: 26, 232, 262–264, 265,

spivakae: 57

Key couplets: male: 79b, female: 56b

succinipenne: 60

luteicornis: 262–263, 264

synthridis: 66

occidentalis: 263–264

texanum: 64–65

Masked Bee. See Hylaeus

trizonatum: 62

Mason Bee. See Osmia

zephyrum: 60–61

Medicago: 71

Leaf-cutter Bee. See Megachile

Megandrena: 31, 98, 99, 112–113

Leiopodus: 232

Key couplets: male: 76b, female: 22b

Lilac. See Ceanothus

enceliae: 112–113

Lithurginae: 157, 227 Lithurgopsis: 194, 227–230 apicalis: 228–229 littoralis: 228

mentzeliae: 113 Megachile: 12, 16, 21, 28, 31, 32, 156, 158, 168, 189–192, 194–206, 222, 228 Key couplets: male: 124a, female: 12a

Lithurgus chrysurus: 227

(Xanthosarus): 204

Loasaceae: 149

apicalis: 199

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INDEX  411

brevis: 195–196

agilis: 266–267

centuncularis: 197, 201

clarkiae: 272

coquilletti: 196

communis:

dentitarsus: 206

coreopsis: 268

fidelis: 202, 203

dagosus: 269–271

frigida: 203–204

grindeliae: 269

inermis: 196–197, 198, 201

lupinus: 270

lapponica: 197, 201

paroselae: 268–269

latimanus: 192, 206

perlusus: 267

melanophaea: 192

stearnsi: 271–272

mellitarsis: 203

submenuachus: 267

mendica: 199

tristis: 267–268

montivaga: 192, 197–198

Melissoptila: 232, 363, 370

onobrychidis: 196

Melitoma: 231

perihirta: 205–206

Melitta: 29, 147, 154–155, 317

pluto: 156

Key couplets: male: 99a, female: 48a

policaris: 201–202

californica: 154–155

pseudobrevis: 196

Melittidae: 147–155

pugnata: 202–203

Melittinae: 147, 151, 154

relativa: 197, 200–201

Mentzelia: 80, 81, 112, 149

rotundata: 156, 198–200

Mesoxaea: 99, 114

sculpturalis: 156

Mesquite. See Prosopis

texana: 192, 200

Mexalictus: 35

Megachilidae: 33, 156–229 Megachilinae: 157, 159, 165, 168, 170, 176, 188, 189, 194, 206, 209, 211, 216, 220, 222, 224

Micralictoides: 27, 36, 79–80 Key couplets: male: 61b, female: 36b linsleyi: 79 ruficaudus: 79, 80

Megachilini: 158, 189, 194

Milkvetch. See Astragalus

Meganomiinae: 147

Miner Bee. See Andrena

Melecta: 232, 265, 275, 284, 329, 332–335, 337

Mining Bee. See Andrena

Key couplets: male: 93a, female: 135a

Mint. See Lamiaceae

(Melectomimus): 332

Morning Glory. See Convovulacae

edwardsii: 332–333 pacifica: 333–335 Melectini: 232, 332, 335, 339, Key couplets: male: 91a, female: 134a Melilotus: 91, 268 Melissodes: 232, 251, 262, 265–277, 325, 326

N Neolarra: 27, 31, 123, 233, 321, 338–339 Key couplets: male: 58a and 112b, female: 130a

Key couplets: male: 79a, female: 56a

alba: 339

(Callimelissodes): 272

californica: 339

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412  INDEX

Neolarrini: 233, 338

laeta: 188

Neopasites: 75, 118, 232

laticeps: 183

Nightshade. See Solanum

lignaria: 156, 180–181, 187

Nomada: 25, 27, 40, 71, 101, 233, 290, 292,

margipennis: 186 montana: 183–184

317–320

nemoris: 186–187

Key couplets: male: 98a and 114a, female:

nigriventris: 178

136a and 144a edwardsii: 318–319

ribifloris: 182–183

hemphilli: 319–321

taurus: 180

Nomadinae: 231, 232, 233, 317, 321, 322, 325,

Osmiini: 28, 32, 158, 159, 165, 168, 170, 176, 188, 194, 222, 223

330, 338, 339 Nomadini: 233, 317

Oxaeinae: 99, 114

Nomia: 12, 14, 29, 35, 71–73 Key couplets: male: 86a, female: 39a foxii: 72 howardi: 72 melanderi: 35, 71–72 tetrazonata: 73 universitatis: 73 Nomiinae: 35

P Panurginae: 32, 97, 98–99, 115, 118, 121, 123, 141, 330 Key couplets: male: 102a, female: 23b Panurgini: 98, 118, 121, 123 Panurginus: 98, 121–123 Key couplets: male: 106a, female: 26a gracilis: 122–123

O

Panurgomia: 151

Oenothera: 64, 272 Onagraceae: 64 Opuntia: 228 Oreopasites: 232, 339–341 vanduzeei: 340–341

Paranthidium: 157, 210, 216, 220–221, 225 Key couplets: male: 118a, female: 11a Jugatorium: 220–221 Paranomada: 233, 290, 292 Parkinsonia: 295

Osirini: 232

Pea. See Fabaceae

Osmia: 26, 32, 33, 156, 158, 170, 174, 176–188,

Pearly-banded Bee. See Nomia

206, 207, 208, 222 Key couplets: male: 127a, female: 14a aglaia: 187–188 atrocyanea: 183

Perdita: 17, 25, 30, 97, 98, 116, 118, 121, 123–141, 338–340 Key couplets: male: 104b and 106b, female: 24b

bruneri: 188

affinis: 135

bucephala: 177–178

albipennis: 131, 137–138

californica: 185–186

albonotata: 129–129

corniforns: 178–179

aridella: 125–126

densa: 183

beatula: 126–127

indeprensa: 188

bellula: 124–125

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INDEX  413

biparticeps: 126

Prosopis: 127

chamaesarachae: 134

Protandrena: 98, 141–146, 330

coreopsidis: 138, 139–140

Key couplets: male: 74a, female: 26b

cowaniae: 132

aethiops: 145–146

crandalli: 133

cockerelli: 143

dasylirii: 130

innuptus: 143–144, 145

discors: 128

irregularis: 144–145 mexicanorum: 142–143

fallax: 136 fallugiae: 132–133

Protandrenini: 97, 98, 141

genalis: 128

Protepeolini: 232

interrupta: 138–139

Protodufourea: 36

lenis: 134

Protosmia: 158, 188–189

lepachidis: 140

Key couplets: male: 125a, female: 15a

micheneri: 139

(Chelostomopsis): 188

minima: 97, 133 moabensis: 129

rubifloris: 189–190 Protoxaea: 26, 30, 31, 99, 114–115

nasuta: 136–137

Key couplets: male: 73a, female: 19a

nevadensis: 135–136

gloriosa: 114–115

oregonensis: 141

Prunus: 103, 178

physalidis: 134

Pseudoanthidium: 157

proxima: 141

Pseudaugochlora: 35

punctosignata: 127–128

Pseudopanurgus: 98, 121, 123, 142, 330

rhois: 129–130

Pterosarus: 142. See also Protandrena

scopata: 138

Ptiloglossa: 83

similis: 140–141

Ptilothrix: 231, 360

stathamae: 128

Pumpkin. See Cucurbita

stephanomeriae: 129

Pure Gold-green Sweat Bee. See Augochlora

tricincta: 138 xanthodes: 127 xerophila: 137 zebrata: 130–131

R Raspberry: 187

Phacelia: 74, 77, 78, 86, 165, 167, 171,

Rediviva: 147

Plantaginaceae: 156, 187

Resin Bee. See Dianthidium

Plasterer Bee. See Colletes

Rhamnus: 139

Polemoniaceae: 271

Rhopalolemma: 232

Polyester Bee. See Colletes

Rophitinae: 35, 36, 74, 75, 79, 80

Poppy. See Argemone

Key couplets: male: 59a, female: 34a

Populus: 234

Rophitini: 35,36

Prairie clover. See Dalea

Rosa: 174

Prickly Pear. See Opuntia

Rosaceae: 91, 95, 105, 178

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414  INDEX

obliqua: 274–275

Rose. See Rosa Rubus: 152, 178, 187

Sweat Bee. See Halictinae

S

T

Salix: 103

Thelesperma: 144

Salvia: 189

Tiquilia: 124

Sambucus: 174, 238, 240

Townsendiella: 74, 148, 233, 320–321

Sandmat. See Chamaesyce

Key couplets: male: 112a, female: 141b

Sclerocactus: 228

ensifera: 321

Scorpion Weed. See Phacelia

pulchra: 321

Senna: 114

Townsendiellini: 233, 320–321

Simanthedon: 232, 363, 370

Trachusa: 29, 32, 157, 212, 216, 224–227

Small carpenter Bee. See Ceratina

Key couplets: male: 119b, female: 11b

Solanaceae: 114, 142, 263

gummifera: 227

Solanum: 114, 142

larreae: 225–226

Solidago: 96

perdita: 226–227

Sphaeralcea: 116, 118–120, 126, 154, 245, 248,

Triepeolus: 68, 83, 114, 233, 251, 262, 265, 272, 275, 322, 325–328

260, 261 Sphecodes: 27, 35, 36, 38, 40, 46, 55, 66–67,

Key couplets: male 84b, female: 137b

116, 123, 330, 340

concavus: 328

Key couplets: male: 70a, female: 132a

penicilliferus: 327

arvensiformis: 67

remigatus: 327–328 subnitens: 326–327

Sphecodosoma: 36 Spurge. See Euphorbia

Triopasites: 233, 290, 292

Squash. See Cucurbita Squash Bee. See Eucera Stelis: 26, 154, 157, 159, 165, 168, 170, 176, 209, 211, 216, 220, 222–224

V Vaccinium: 152

Key couplets: male: 115a, female: 144b

Verbesina: 145

laticincta: 222–223

Vernonia: 195

perpulchra: 223–224 Stephanomeria: 128 Sumac: 174, 238

W

Sunflower. See Helianthus

Willow. See Salix

Sunflower Bee. See Dieunomia; Svastra

Wirelettuce. See Stephanomeria

Svastra: 10, 30, 114, 232, 262, 265, 272–275,

Wool Carder Bee. See Anthidium

326

White-faced Bee. See Hylaeus

Key couplets: male: 80a, female: 57a duplocincta: 273–274

02 CBoWNA pp230-416.indd 414

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INDEX  415

X

Y

Xeralictoides: 80, 150

Yellow-faced Bee. See Hylaeus

Xeralictus: 27, 36, 80–81

Yucca: 234

Key couplets: male: 62a, female: 37a bicuspidariae: 81 timberlakei: 81 Xeroheriades: 158 Xeromelecta: 337 Xylocopa: 30, 32, 68, 180, 181, 194, 231, 233–238, 302

Z Zacosmia: 232, 275, 335–336 maculata: 335–336 Zikanapis: 83 Zygophyllaceae: 114, 263

Key couplets: male: 89a, female: 46a californica: 234–235 tabaniformis: 235–237 sonorina: 237–238 Xylocopinae: 231

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