Common Nymphs of Eastern North America: A Primer for Flyfishers and Flytiers 9780271058863

Citation preview

common nymphs of eastern north america

common nymphs of eastern north america

a primer for flyfishers and flytiers

Caleb J. Tzilkowski and Jay R. Stauffer Jr.

the pennsylvania state university press University Park, Pennsylvania

Library of Congress Cataloging-in-Publication Data

Tzilkowski, Caleb J., 1975– Common nymphs of eastern North America : a primer for flyfishers and flytiers / Caleb J. Tzilkowski and Jay R. Stauffer, Jr. p. cm. Includes bibliographical references and index. Summary: “A guide for identifying and imitating nymphs, with a focus on flyfishing. Also provides information useful to students, stream conservationists, and scientists concerned with monitoring the health of stream ecosystems”—Provided by publisher. isbn 978-0-271-20450-5 (pbk. : alk. paper) 1. Fly tying—East (U.S.). 2. Fly tying—Canada, Eastern. 3. Flies, Artificial—East (U.S.). 4. Flies, Artificial—Canada, Eastern. 5. Nymphs (Insects)—East (U.S.)—Identification. 6. Nymphs (Insects)—Canada, Eastern—Identification. I. Stauffer, Jay R. II. Title. SH451.T98 2011 799.12’40974—dc22 2010039069

Copyright © 2011 The Pennsylvania State University All rights reserved Printed in China by Asia Pacific Offset Published by The Pennsylvania State University Press, University Park, PA 16802–1003 It is the policy of The Pennsylvania State University Press to use acidfree paper. Publications on uncoated stock satisfy the minimum requirements of American National Standard for Information Sciences— Permanence of Paper for Printed Library Material, ansi z39.48–1992.

contents



List of Figures  vii Preface  ix

1 nymph ecology  1 2

caddisflies  9 Netspinner or Tan Caddisflies  13 Little Black or Fingernet Caddisflies  16 Green Caddisflies or Green Rock Worms  18 American Grannom and Apple Caddisflies  21 Case-Maker Caddisflies  23 Smokey Winged Sedges  25 Dark Blue Sedges  26 Autumn Mottled Sedges  27

3

mayflies  29 Little Blue-Winged Olives  32 Mahogany Duns or Blue and Black Quills  34 Flatheaded Mayflies  36 Quill Gordons, Pink Ladies, and Gray-Winged Summer Quills  37 March Browns or Gray Foxes  39 Cream and Light Cahills  40 Hendricksons, Red Quills, and Sulphurs  42 Green and Yellow Drakes  45 Slate Drakes or Great Leadwings  47

4

stoneflies  49 Green Stoneflies or Sallflies  53 Roachflies  55 Common Stoneflies or “the Stones”  56 Little Yellow Stoneflies  59 Eastern Giant Stoneflies  60

5

true flies  64 Midges  67 Black Flies  69 Crane Flies  72 Horse Flies and Deer Flies  73 Snipe Flies  75

6

hellgrammites and other arthropods  77 Hellgrammites  77 Sowbugs  79 Scuds  81 Crayfish  83

appendix a Caddisfly Attributes and Simple Fly Patterns  87 appendix b Mayfly Attributes and Simple Fly Patterns  90 appendix c Stonefly Attributes and Simple Fly Patterns  94 appendix d Dipteran Attributes and Simple Fly Patterns  96 appendix e Hellgrammite and Noninsect Arthropod Attributes and Simple Fly Patterns  98 appendix f Generalized Caddisfly and Mayfly/Stonefly Anatomy  100

References  102 Index  103

figures

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34

Giant stonefly egg mass  4 Recently molted chocolate dun nymph  4 Grannom caddisfly pupa and case  6 Chironomid midge pupa  6 Generalized caddisfly characteristics  10 Underwater photograph of netspinner caddisfly nets  10 Netspinner caddis  14 Tan caddis larva on scud hook  14 Netspinner caddis on top of its nets  15 Little black or fingernet caddis  17 Little black caddis larva on nymph hook  17 Green caddis or green rock worm  19 Green caddis larva on nymph hook  19 Ventral view of green caddis pupa  20 American grannom caddis or apple caddis  22 Grannom caddis on scud hook  22 Case-maker caddis  24 “Giant stick worm” on nymph hook  24 Smokey winged sedges  26 Gravel-cased nymph on hook  26 Dark blue sedge  27 Autumn mottled sedges  28 Generalized mayfly characteristics  30 Well-developed wing pads on a little blue-winged olive mayfly  31 Little blue-winged olive  33 Little blue-winged olive nymph on nymph hook  33 Mahogany dun, blue and black quill  35 Dark quill nymph on nymph hook  35 Flatheaded mayfly nymphs  36 Quill Gordon, pink lady, and gray-winged summer quill  38 Quill Gordon nymph on nymph hook  38 March brown or gray fox  40 March brown nymph on nymph hook  40 Cream light cahill  41

viii  |  figures

35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77

Emerging cahill on nymph hook  41 Hendricksons, red quills, and sulphurs  43 Hendrickson and red quill nymph pattern  45 Emergent sulphur nymph on nymph hook  45 Green yellow drake  46 Green drake nymph on nymph hook  46 Slate drake, great leadwings  47 Isonychia on nymph hook  48 Generalized stonefly characteristics  50 Dorsal view of predaceous stonefly mouth  52 Shed common stonefly exoskeletons  52 Sallfly or green stonefly  54 Green stonefly nymph on nymph hook  54 Roachfly  56 Roachfly on scud hook  56 Common stonefly  57 Common stonefly on nymph hook  57 Little yellow stonefly  59 Sally stonefly on nymph hook  60 Eastern giant stonefly  61 Giant stonefly on nymph hook  61 Crane fly larva  66 Midges  68 Assorted midge patterns on hooks  68 Black flies  70 Black fly on scud hook  70 Black fly larva labral fan  71 Crane fly (Antocha)  72 Mini cream crane fly on scud hook  72 Hexatoma sp. crane fly  73 Horse flies and deer flies  74 Horse fly on nymph hook  74 Water snipe flies  75 Snipe fly on nymph hook  76 Hellgrammite  78 Hellgrammite on nymph hook  78 Sowbug (ventral view)  80 Sowbug (dorsal view)  80 Gray sowbug on nymph hook  81 Scuds  82 Amber scud on scud hook  82 Crayfish  84 Crayfish on nymph hook  84

preface

The appeal of dry fly-fishing is undeniable, but if the only time you can go fishing does not coincide with rising trout, nymph fishing (nymphing) can be very productive, exciting, and rewarding. The purpose of this book is to help flyfishers and flytiers accurately imitate the most common nymphs and aquatic animals on which trout feed in eastern streams. Not only will this book help novice and seasoned anglers catch more trout, but it will also add to your understanding of and appreciation for the animals that we imitate with fly patterns.

There is certainly nothing wrong with the fact that

many flyfishers choose to fish exclusively with dry flies. It is undeniably gratifying to watch a cagy trout rise from the shadows to either sip a tiny midge pattern or explode into the air after a skittering caddis dry fly. On spring and summer nights on many trout streams, you can see people sitting and waiting for the hatch or for a trout to rise before they make a cast. Again, there is nothing wrong with taking in the splendor of a warm and peaceful spring or summer night and watching the water flow. Different flyfishers have different reasons for fishing only dry flies; nonetheless, some of us enjoy catching fish as frequently as possible and are not patient enough to wait for rising fish. Moreover, most of us must take advantage of the limited time to fish when we can get it, even if it does not coincide with good dry fly-fishing.

Some fly-fishing purists consider dry fly-fishing to

be the only worthy use of their fishing time—presumably because nymph or streamer fishing is not enough of a challenge or sport for them. The majority of anglers who are sitting and waiting for the hatch, however, are probably not purists. More likely, they have never had a lesson in matching the “nymph hatch.” As with most things, a

x  |  preface

little bit of knowledge goes a long way. This book offers that knowledge, along with detailed images and information about the nymphs that we most often encounter in eastern trout streams. This knowledge, in combination with a little bit of investigation, will help even beginning anglers choose the most appropriate nymphs to fish on their local streams throughout the year.

Experienced nymph anglers can usually catch at

least some fish on any trout stream under even the poorest conditions. They are able to consistently catch fish for three main reasons. First, good nymphers can “read the water” and identify where feeding fish are likely holding. Second, they can naturally drift a fly right along the stream bottom, usually with a “dead drift.” Those two things are probably most important in catching fish with nymphs and require some experience and practice. The third ingredient of nymph fishing is the subject of this book—matching the nymph. You are probably already familiar with two common nymph patterns: the hare’s ear and pheasant tail nymphs. Both patterns do a reasonable job at imitating a variety of mayfly nymphs. Unfortunately, these patterns do not always work well; on some occasions, they do not work at all. We know that an Adams dry fly pattern can perform well for several gray mayfly hatches, but they are obviously not as effective when fish are taking big green drakes at night or tiny morning midges from the water surface. The same idea applies when fish will not move to your size 10 tan caddis nymph but will readily gobble a size 16 green caddis nymph. This is the case because, in large part, trout are selective feeders. Exceptionally big trout become even more selective (particularly brown trout) and will nocturnally hunt larger prey, such as other fishes and large crayfish. What this means is that all but the biggest trout will consistently feed on the kinds of prey that are most available to them at any given time. Similar to masses of trout feeding at the surface on abundant and easily available dead or dying adult mayflies, trout will feed on certain nymphs when they are particularly available as prey. This guide will help you identify what kinds of nymphs are likely to be most effective at different times of the year and in different types of streams.

Preface  |  xi



We suggest patterns that do very well at imitat-

ing the various nymphs, but remember that creativity and innovation are a large part of fly-tying’s appeal. Thanks to microscopy and digital photography, this guide provides flytiers the ability to design their own nymph patterns based on high-resolution images. That, after all, is one of the most rewarding parts of fly-tying—fooling wary trout with something you have made with your own hands and imagination. An equally important objective of this guide is to give flyfishers and flytiers a better understanding of and appreciation for the animals that we imitate with nymph patterns. For most anglers, there is a lot more to fishing than catching fish. That seems to be particularly true for people who have “caught the bug” of fly-fishing. We hope that this guide makes your fishing trips more rewarding by helping you understand animals that we imitate and their importance to trout streams and adjacent ecosystems.

Successful nymph fishing can be viewed in the same

way that journalists approach reporting the news, which is the “five Ws and an H” (who, what, where, when, why, and how). Unfortunately, many flyfishers and flytiers overcomplicate nymph fishing due to a lack of knowledge about the nymphs that we imitate. In this guide, we hope to overcome that by adopting an approach to the five Ws that does not exist elsewhere in the fly-fishing and fly-tying literature. The “who” in our case are the organisms that nymph patterns imitate. As you are probably aware, many fishing and fly-tying books have drawings of nymphs or, more frequently, recipes and pictures of nymph patterns for the reader to imitate. What we have done in this book is provide detailed images of the real nymphs (the who), our suggested patterns to imitate them (the what), information about their habitat (the where), and their life histories and behavior (the when and why). We have also provided basic tips on the “how” of nymph fishing, but that is not the primary goal of our guide. Many books detail various nymph-fishing techniques, so we will not reinvent the wheel. Instead, we describe a few basic premises. The five Ws in our book will help you catch more trout and, perhaps more important, make nymph fishing a more interesting and rewarding experience.

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2

3

4

5

6

Nymph Ecology

The animals in this guide are aquatic arthropods—many of them are insects, and a few are crustaceans. “Aquatic” means that these organisms live underwater during at least part of their lives, and “arthropod” means that they have a hard exoskeleton and stiff, jointed appendages that in some cases are modified into legs, mouth parts, or antennae. Most of us learned somewhere along the way that insects are arthropods whose bodies consist of a head, thorax, abdomen, three pairs of legs, and typically one or two pairs of wings. That definition does not always apply to aquatic insect larvae, which look more like worms than insects at first glance. Insects in this guide are terrestrial as adults—in fact, only a few types of aquatic insects (mostly beetles) spend their entire lives underwater. Consequently, many artificial nymphs are designed to imitate immature, larval stages of aquatic insects. The adult stages of insects in this guide live (often very briefly) on land or in the air. The rest of their lives are spent in the stream. Noninsect arthropods in this guide are crayfish, scuds, and sowbugs. Collectively, these animals are termed crustaceans and spend their entire lives under water.

By no means is this a comprehensive account of

all nymphs found in eastern streams. At the end of this guide we provide a list of resources for readers who want more detailed information about nymphs and nymph fishing. Consider that nearly forty thousand known insect species spend part of their lives in freshwater habitats, in addition to thousands of other arthropod and molluscan (snails and clams) species throughout

2  |  common nymphs of eastern north america

the world. For most flyfishers and flytiers, identifying nymphs to the species level is generally unnecessary. Trout and other fish that feed opportunistically are not at all concerned with what humans name nymphs. Fish recognize preferred prey items and when they are most available in the stream. What we as anglers need to do is match or at least approach that level of knowledge. Specifically, we need to know which nymphs are most available when we are fishing and match their appearance in terms of size, color, silhouette, and, to a lesser degree, movement. That information is provided in this guide for most nymphs in eastern streams.

Eight major groups (orders) and selected families

within each order are discussed. For each family we have provided images of commonly encountered groups of species (genera), suggested imitations, emergence dates, and information regarding their behavior and ecological role in streams. Nymph presentation and size are admittedly more important than appearance for nymph fishing, but patterns in this guide work better than the standard patterns when fish are finicky. The patterns we present are intended for those who want inexpensive, simple, yet very effective flies. There are artistic flytiers who create gallery-worthy representations of the real nymphs, and there is no doubt that these flies would be very effective, but who wants to lose artwork to a rock or overhanging tree limb? A major benefit of this guide is that it provides detailed images of living nymphs so that you no longer have to rely on standard patterns like the hare’s ear, prince nymph, and pheasant tail. You can invent your own patterns—and how much detail your imitations will have is up to you.

Ranges of emergence times are presented in the ap-

pendixes for the various adults of the represented families. These tables give flyfishers time frames for when different patterns should be most effective. Many books and Web sites contain far more specific regional hatch charts than those contained in this book. Moreover, the best way to learn about local insect emergences if you are new to an area or stream is usually to go to a local fly shop and get advice. Most guides and shop owners are more than happy to share information, especially if you

Nymph Ecology  |  3

buy a few small items, such as flies or tippet material. By knowing which adult insects are most available, you will be able to use this guide to make better decisions about which kinds of nymphs to fish instead of relying on trial and error. For example, patterns that copy grannom caddis larvae and pupae tend to be largely unproductive after the grannom caddis have emerged.

Some of the most famous Pennsylvania trout

streams are mentioned in this guide, but you can easily apply the information to streams from Maine to Georgia. As you travel, carry this book and inspect rocks and logs in your favorite trout streams—you will find many of the same organisms. Habitat, water temperature, and water quality largely influence the types of nymphs that you will find. A general rule of thumb is that the better the water quality, the more types of organisms you will find. In this book, we refer to classic limestone streams (e.g., Spring Creek) and freestone streams (e.g., the Little Juniata River). These broad classifications of streams generally support somewhat different types of aquatic organisms, which we describe throughout this book. The more you know about your favorite streams, the better success you will have trying to match the “nymph hatch.”

The longevity of aquatic insects differs. For example,

dragonflies and hellgrammites can live for more than three years underwater, whereas other groups (e.g., some midges and mayflies) complete their entire life cycles from egg to adult in less than two weeks. As many as four life stages may be required to complete aquatic insect life cycles: egg, larva (pl., larvae), pupa (pl., pupae), and adult. Many aquatic insects have all four stages and are termed holometabolous, whereas other groups, such as stoneflies and mayflies, lack the pupal stage (i.e., are hemimetabolous) and transition directly from the nymph to the adult. Flyfishers and flytiers generally use the term “nymph” when referring to all kinds of subsurface fly patterns. We will continue that practice in this guide to avoid confusion. To be clear, though, the term “nymph” has specific meaning for entomologists. They define nymphs as the larval stage of insects that do not have a pupal stage (e.g., mayflies and stoneflies). These groups transform from larvae directly into adults.

4  |  common nymphs of eastern north america



Aquatic insect eggs that are laid in or near the

stream eventually hatch as larvae. Females deposit eggs in many ways, and their behaviors can often aid entomologists when identifying species. Some species fly relatively high over the stream and shower individual eggs or egg masses onto the water surface. Females of other species fly low and dip their abdomens into the water, which causes eggs to be released, and yet another

fig. 1 Giant stonefly (Pteronarcys sp.) egg mass

fig. 2 Recently molted chocolate dun (Eurylophella) nymph

Nymph Ecology  |  5

groups (e.g., many caddis) swim or crawl underwater to glue their egg masses to the substrate. After laying fertilized eggs, female adults die and become food for trout and a variety of other animals that live in or near the stream. These dying or dead adults sometimes stimulate the feeding frenzies that many flyfishers use to their advantage while fishing for trout or smallmouth bass. Sizes and colors of eggs vary widely from black to nearly fluorescent greens and oranges. Some egg masses greatly expand when in contact with water to form jellylike masses that appear similar to amphibian eggs. Different colors, shapes, and sizes of fly patterns imitate fish eggs, but we are unaware of any insect egg patterns. Many dry fly patterns imitate female adult mayflies, stoneflies, and caddis that have brightly colored egg masses on the tips of their abdomens. Although we have never tried it, a size 28 insect egg pattern would probably work well at times, too. On more than one occasion in several different streams, we have found brook trout and brown trout with dozens of stonefly egg masses (fig. 1) in their stomachs. Despite their small size, these abundant egg masses drifting by at the peak of an emergence would be an easy-to-catch and energy-rich meal. If the egg masses make it past trout and other predators, they sink to the stream bottom and often have a sticky coating that adheres them to stones, logs, and other submerged structures. When fishing dry flies, the term “hatch” often is used when adult aquatic insects are coming off the water. The most appropriate term for these events would be “emergence,” because the adults we see flying around already hatched as larvae weeks or months earlier. Eggs of some species develop very quickly, but others do not develop for many months. They do so by remaining in a dormant stage called diapause, which is an adaptation that allows eggs to avoid unfavorable conditions (e.g., water temperature extremes or lack of surface water flow). Once conditions become favorable, larvae hatch and begin to grow, often very rapidly.

The length of time that insects spend as larvae

depends on many factors, including the species and latitude where they live. Many species spend much of their life cycle in the egg stage due to diapause, but the

6  |  common nymphs of eastern north america

larval stage is usually the longest period aquatic insects are readily available as food for fish. All larvae mature by molting, which means that they shed their exoskeleton and then grow into their new “skin.” Nymphs that have recently molted are often very light in color, usually shades of yellow or cream (fig. 2). Time periods between molts are called instars and are often used to count larval growth stages. Most terrestrial animals grow primarily during the summer months, but this is not necessarily fig. 3 Grannom caddisfly (Brachycentridae) pupa and the case where it spent its larval and pupal stages

fig. 4 Chironomid midge pupa just prior to its emergence

Nymph Ecology  |  7

the case for many aquatic insects. Trout streams are cold environments, which you already know if you enjoy wetwading. Even though stream water is particularly cold during winter, often near 0°C (32°F), many aquatic insects put on most of their body mass during winter. Excellent examples of this are the winter stoneflies or snowflies (family Capniidae), which are very similar in size and appearance to the green stonefly (family Chloroperlidae) nymphs. These stoneflies emerge during some of the coldest winter months, usually beginning in February, to lay their eggs. After only three weeks, the eggs hatch and the microscopic nymphs grow and molt three times until April. From then until autumn (usually October), the nymphs are in a state called aestivation or quiescence, burrowed deep in the stream bottom with their heads tucked under their thoraxes. This condition is very similar to hibernation, but instead of avoiding winter, aestivation usually takes place to avoid the relatively hot and dry conditions of summer. Growth resumes in autumn and is rapid until adults emerge, often flying over snow to eat algae from the surface of terrestrial vegetation.

To transition from their aquatic to terrestrial stage,

many insects (except stoneflies and mayflies) pupate in a manner similar to that of moths and butterflies. Many pupae, particularly caddisflies, mature while inside the cases they used as larvae (fig. 3), whereas others build special cases just prior to entering the pupal stage. Although caddis may seem entirely safe from becoming prey while enclosed in their stone cases, we have found large trout with nearly one hundred pulverized cases in their stomachs. Pupae in other groups, such as midges, are presumably easily digested because their pupal cases are usually nothing more than toughened skin (fig. 4). Midge pupae and emergers are a favorite trout food. When you see trout “sipping” midges, they are probably feeding on midge pupae that are rising to or stuck in the surface film. Metamorphosis takes days or weeks, and pupae then shed their pupal skin and emerge as adults. Some organisms in this guide will have multiple generations per year, with an emergence of adults with each generation, whereas some large nymphs such as stoneflies and hellgrammites take two or three years to ma-

8  |  common nymphs of eastern north america

ture into adults. Generally speaking, nymphs that grow to larger maximum sizes have longer aquatic life stages.

To use this guide effectively, a general understanding

of nymph anatomy (see appendix F) will be very helpful. We use two very broad categories of nymphs in this guide—namely, insects and noninsects. Again, scientifically speaking, the term “nymph” is most appropriately used when referring to the larval stage of insects that do not have a pupal stage. Caddisfly, mayfly, and stonefly larvae have six legs and segmented bodies, whereas “true flies” (order Diptera), such as crane fly and horse fly larvae, are more cylindrical and do not have legs or readily distinguishable body segments. The thorax comprises the first three body segments behind the head to which the legs are (or would be) attached. Atop the thorax of mayfly and stonefly nymphs are wing pads that contain the developing adult wings. The remainder of the body behind the thorax is referred to as the abdomen. In the same way that fish need gills, gills help mayflies, most caddis, and some stoneflies obtain dissolved oxygen from water. At the opposite end from the head, many insects have long tail-like filaments called caudal filaments. Although not really tails, we often simplify descriptions by referring to these filaments as tails.

One of the most important parts of fly-tying is to reproduce a silhouette that most closely resembles that of the real nymph. To do so, use the pictures in this guide to replicate the relative width and length of the organisms’ body parts. Many aquatic insects have gills protruding from their abdomens that can be imitated with various materials, such as wrapped herl from a peacock or ostrich.

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6

Caddisflies (Trichoptera)

Caddisflies, or caddis, do not have the legendary status that mayflies have garnered from flyfishers, but as a group they can dominate stream insect communities, are an integral part of functioning stream ecosystems, and are a very important food for trout. Many of us know that caddis adults are a favorite for trout, but because caddis larvae are available to trout for much longer than adults, fly boxes should contain their imitations year-round (see appendix A). Caddis larvae share several common identifying characteristics among families (fig. 5) and appear somewhat similar to butterfly caterpillars. Caddisflyidentifying characteristics include (1) very short, almost invisible antennae, (2) no wing pads on the thorax like those on mayflies and stoneflies, (3) three pairs of legs on the thorax, (4) single or branched gills on abdominal segments, (5) two anal claws on the end of the abdomen, and (6) often, a portable or attached case made of stones, sand, and/or vegetation.

Caddisflies are similar to moths and butterflies (or-

der Lepidoptera) in appearance and several other ways, but a very noticeable difference between most of the Lepidoptera and caddis is that caddis larvae live underwater. We say most because quite a few moth species have aquatic larvae. Unlike true nymphs (e.g., mayflies and stoneflies), caddis are holometabolous, meaning they have a complete life cycle with four distinct stages (egg, larva, pupa, adult). Most caddisflies have one generation per year, but some caddis species spend two years as larvae before adulthood. To protect themselves from predation and a harsh and chaotic underwater environment, many caddis construct portable cases or retreats that they carry or attach to the stream bottom. As devel-

10  |  common nymphs of eastern north america

Portable case

No wing pads Soft abdomen

Anal claws

opment continues, larvae periodically have to leave their cases and build larger ones that accommodate their bigger bodies. Finally, caddis will build silk cocoons inside their cases to metamorphose into adults.

Scientists have organized caddisflies into three

groups, called suborders or superfamilies, according to their case-building behavior. Caddis larvae in the group Annulipalpia live in nets or retreats they make from silk, somewhat like those of spiders (fig. 6). They secrete silk fig. 5 Generalized caddisfly characteristics shown on an autumn mottled sedge (Uenoidae) larvan

fig. 6 Underwater photograph of a series of small and large netspinner caddisfly nets

Caddisflies  |  11

from glands in their mouths to build the nets, which filter algae, detritus, and macroinvertebrates. Again, like spiders, the larvae then collect and eat captured food items from the net. Another characteristic of this group is their silk cocoons with small openings at each end that allow water and oxygen to circulate. If you pay attention to areas with moderate to swift current, you will see these nets. Different caddis live in different microhabitats, but at least enough water needs to be flowing to carry suspended particles into the nets. If you look on the surface of the rocks, you can often see hundreds or thousands of caddis nets undulating in the current within a few square feet. It is truly amazing that each one of those nets has a predator lurking inside, picking dozens of other kinds of animals from its entanglement. Another caddis group (Spicipalpia) also makes silk cocoons, but the cocoons do not have openings in them. Instead of making a retreat, these caddis are free living and either do not have a case (e.g., green caddis) or make and carry cases made of mineral or organic materials (e.g., dark blue sedge). Members of the third group of caddis (Integripalpia) do not make silk cocoons; instead, they pupate in their final larval cases after attaching them to rocks or logs. Grannom caddis (Brachycentridae) are an example of caddis larvae that pupate in their larval cases.

Most caddis species have five larval instars and grow

incrementally larger between each molt. After their final molt, caddis larvae either make silk cocoons or seal the cases in which they are living to begin their metamorphosis into adults. During the prepupal stage inside the cocoons, which can last for two weeks, larvae become stouter and their skin takes on a leathery texture. Caddisflies continue to develop as pupae for another two to three weeks and then chew their way out of the enclosed cocoons or cases. The pupae swim and float their way to the water surface. As the pupal shuck splits and breaks the water surface, an air bubble is formed in which the caddis stays dry and then escapes. Some caddis use their shuck as a raft to dry their wings before flying away. During these brief moments, caddis are most vulnerable to trout and other predators. The next time you are on the water during a caddis emergence, try to determine

12  |  common nymphs of eastern north america

whether trout are feeding on adults or emergers that are just shedding their shucks. Given the chance, trout will most often take the emerger rather than the adult because emergers cannot fly and are much easier to catch. You can often see adult caddis skitter across the water to escape from rising trout, whereas emergers generally do not stand much of a chance to escape.

Caddis adults live for approximately one month and

spend much of their time feeding or resting on streamside vegetation. After mating, females lay from several to as many as eight hundred eggs, either individually or in jellylike masses. On adult caddis patterns, egg masses are often imitated with green, yellow, or orange dubbing on the end of dry fly abdomens. Many caddis fly along and drop their eggs at the water surface, while others crawl or swim underwater to deposit their eggs on the underside of rocks or submerged vegetation.

Thousands of small “hairs” can be seen on adult

caddis under magnification. These hairs help keep caddis emergers and adults dry by forming a silvery air bubble around them. For some caddis adults, that bubble allows them to stay under water for thirty minutes while they attach their eggs to the underside of rocks. In many instances, the adult egg-laying females do not return to the water surface, making them very vulnerable drifting prey for trout. The swimming behavior of many female adult caddis is why numerous traditional wet fly patterns (e.g., leadwing coachman) perform well during several caddis emergences. A good strategy during these times is to fish two flies—either a traditional dry fly or emerger on the surface, with a wet fly suspended as a dropper to imitate the swimming, dying, or dead adult.

Caddisflies, mayflies, and stoneflies usually indicate

good water quality; however, some caddis that are most familiar to flyfishers are rather tolerant to common types of water pollution or habitat degradation. For example, you can often overhear flyfishers discussing “how clean the stream is” because of all the tan caddis (Hydropsychidae), midges, or sowbugs that are on the rocks. The abundance of nymphs alone does not necessarily indicate a “healthy” stream. It is more important to consider the diversity, or variety, of organisms that you can find. Many

Caddisflies  |  13

streams have caddisflies crawling all over the stream bottom, but, unfortunately, many of these may be pollutiontolerant caddis species. In some instances, sensitive caddis species are now extirpated (locally extinct), and the tolerant ones use the food and space of the extirpated species. As you look around the rocks in your favorite trout streams, remember that it is not just the quantity of organisms you find, it is also the number of different kinds of nymphs that can help tell you the condition of the stream. The fact that many eastern streams support wild brown trout and/or rainbow trout does not necessarily mean that the streams are as healthy as they could be. Remember, the native trout throughout most of the Northeast is the brook trout, which is now absent from many of our biggest and famous trout streams where they historically occurred. A similar situation has happened to populations of many other less conspicuous aquatic species, including insects, crustaceans, and mussels.

Netspinner or Tan Caddisflies (Hydropsychidae) up to 30 mm (1.2 inches)

Netspinner caddis live only in flowing waters, but different species inhabit many different kinds of streams— more than 150 species exist throughout North American streams, from headwaters to large rivers. This group of caddisflies is very important to stream ecosystems because of its widespread distribution and its typically great abundance. When in doubt, imitating these larvae is usually a good bet because they are exceptionally common and a very important part of trout diets.

As their name implies, these larvae make parachute-

like nets to capture food from the current (fig. 9). These caddis weave nets between existing materials or erect poles at the front of their small huts to hold the mesh.

To imitate emerging caddis, tie a standard dry pattern without hackle or sparse wing material so that it rides low on the water, right in the surface film. Use synthetic material or squirrel body hair to imitate the trailing shuck, and fish it as you would a dry fly.

14  |  common nymphs of eastern north america

Larvae then go into the retreat and eat the food as it gathers on the mesh. Netspinners aggressively defend their feeding territories, but territory size depends on the abundance of drifting food. While defending their feeding areas, some species in this group produce a warning sound by rubbing the underside of their heads across structures on their legs. If that is not enough of a deterrent, the larvae will actively defend their space on the rocks. Netspinners live in the majority of eastern fig. 7 Netspinner caddis or tan caddis

fig. 8 Tan caddis larva on a size 14 scud hook

Caddisflies  |  15

streams, and some species can be very abundant in organically polluted streams downstream from wastewater treatment plants and fish hatcheries. Part of the reason some of these caddis can live in oxygen-depleted waters is that they have highly developed gills along their abdomens that allow them to efficiently draw oxygen from water, even when concentrations are low.

Caddis pupa patterns can be very effective just

before and during hatches. Until caddis shed their pupal skin (shuck), they are easy and nutritious prey for waiting trout. A standard pupa pattern has a dubbed body, goose or grouse quill wings, wrapped hen hackle, and a dark head. Coloration varies among species and populations, but as long as you have a variety of tan, green, olive, and yellow-orange patterns, you will be well prepared. Netspinner adults are tan, yellow, orange, or brown depending on the species and are similar to lar-

Larval coloration is usually green, brown, olive, or a blend of those colors. If you stock your fly box with netspinners in those colors from size 12 to 18, you will be well prepared.

fig. 9 Netspinner caddis crawling on top of its pair of parachute-shaped nets

16  |  common nymphs of eastern north america

vae in appearance. Adult females in this group swim to bottom rocks and lay their eggs in a leathery mass; consequently, wet flies that imitate the living and expired adult females can be very effective during tan caddis hatches.

Little Black or Fingernet Caddisflies (Philopotamidae) up to 17 mm (0.5 inch)

Several common names are used to describe emergences of different little black caddis species, but as implied by their name, these small caddis are generally very dark as adults. As larvae, their coloration is much different and consists of brilliantly colored yellowish-orange bodies with long, tan heads. Three genera and approximately forty species of little black caddis exist throughout North America—some are common in small, cool eastern streams, whereas several species are abundant in larger, comparatively warm streams.

These larvae make nets in protected areas under

rocks or logs in swift currents. They tend not to build nets in the fastest stream current, but they need flowing water to carry suspended food particles into their nets. They are often abundant in pocket water of riffles where eddies form and in the tailouts of riffles and runs. Their silk is the finest (1–15 microns) of any caddis and their nets are relatively long and gently curved, similar to a horn of plenty or black powder horn. The nets filter microbes, fine detritus, and other small animals as water flows through them. Little black caddis larvae slowly move around the net, eating trapped material after scraping it off with a large T-shaped upper jaw structure. As a group, fingernet caddis are somewhat sensitive to human disturbances such as pollution and removal of streamside vegetation.

Emergence of these caddis often overlaps with gran-

nom caddis on streams where both types of caddisflies exist. We have talked to quite a few people who thought they were “small grannoms,” but, in fact, they are as taxonomically different as brook trout and largemouth bass. Swarms of these caddis are often mistaken for

Caddisflies  |  17

“gnats” along the banks or over shallow stream sections. These shallow, near-shore areas are often prime little black caddis habitat because of moderate stream flows. Although these larvae tend not to live in the swiftest stream currents, they often drift as trout prey—and the suggested pattern can be unbeatable on early spring afternoons. Because this pattern is a relatively early caddis emergence, it is generally most productive early in the year; nonetheless, it works well in all months, likely fig. 10 Little black or fingernet caddis

fig. 11 Little black caddis larva tied on a size 14 2X nymph hook

18  |  common nymphs of eastern north america

because it is a simple pattern that also resembles many other types of aquatic insect larvae (e.g., crane flies and midges).

Green Caddisflies or Green Rock Worms (Rhyacophilidae) up to 30 mm (1.2 inches)

Although many caddisflies are green as larvae, rhyacophilid caddis probably garnered the name “green caddis” because they do not make cases or retreats like most other caddisflies do, making them more conspicuous to us than many other caddis. Because of their bright green and unhidden bodies, they probably deserve the common name more than most other greenbodied larvae. In some areas, green caddis are also known as rock worms even though they only slightly resemble true worms. As a group, green caddis are considered sensitive to certain types of pollution; nonetheless, several relatively pollution-tolerant species of these caddis are very abundant in streams that receive large quantities of human and agricultural waste, such as Spring Creek and Penns Creek in central Pennsylvania. Because various species of this group can live in streams with different underlying geology and water quality, at least some green caddis will occur in trout streams

The suggested pattern uses a strip from a thin plastic bag as a shellback. Many nymph patterns should have a hint of shiny or flashy appearance when wet—especially caddis larvae, scuds, and crane flies. This flash simulates the minute glare that can be seen shining off nymph exoskeletons and trapped air bubbles. To tie shellbacks, cut a strip of plastic bag slightly wider than the body and tie it in before dubbing. After wrapping the dubbing, fold the plastic strip forward and make sure to rib the plastic with copper, gold tinsel, or monofilament for two reasons. First, it makes the segmented body characteristic of the larva, and second, it greatly extends the “life” of the fly. You can add legs to the pattern by wrapping a brown or tan hackle from grouse or partridge breast or by tying in small rubber legs or tail feather fibers.

Caddisflies  |  19

throughout North America. Their widespread distribution throughout a variety of stream types is reflected by the Greek origin of their scientific name—rhyaco (stream or torrent) and philia (fondness).

Green caddis live in swift stream currents and hunt

freely under boulders and in clumps of leaves, moss, or algae. Unlike many other caddis, this group lacks the abdominal gills present on the abdomens of many other caddis families. Their lack of gills is presumably why fig. 12 Green caddis or green rock worm

fig. 13 Green caddis larva on a size 14 2X nymph hook

20  |  common nymphs of eastern north america

these larvae need to live in tumbling currents where water becomes saturated with oxygen. As they move through riffles searching for prey, these caddis attach a thread of silk to the stream bottom, which serves as a safety harness similar to those worn by mountain climbers. Because they are not particularly strong swimmers, these and many other caddis larvae are easy meals for trout and other fish if they lose their hold on the stream substrate (stream bottom). Some species can be as large as 30 millimeters (more than 1 inch), but most are usually half that size. Regardless of how big they are, these caddis are amazingly efficient predators and will eat any organism small enough for them to subdue, including black fly, mayfly, midge, and other caddisfly larvae. Particularly, large green caddis have been known to cut through cases of equally large caddis, then attack, kill, and devour the soft-bodied larvae or pupae inside.

Although these caddis do not live in cases, they must

make protective structures while they pupate. When they are ready to metamorphose, the larvae build domes of small stones, allowing just enough space among the stones to permit water circulation. After the dome is

fig. 14 Ventral (underside) view of green caddis (Rhyacophilidae) pupa inside its cocoon and puparium

Caddisflies  |  21

built, the larvae crawl inside and encapsulate themselves in tough, leathery cocoons of silk (fig. 14). During June and July, green caddis tend to emerge in the afternoon into the evening by chewing through their cocoons and swimming to the water surface.

American Grannom or Apple Caddisflies (Brachycentridae) 8–11 mm (0.3–0.4 inch)

Grannom caddis are very abundant in many eastern streams, and their emergence can be awe inspiring, with hundreds of thousands of adults flying upstream at the same time to mate and lay eggs. These caddis occasionally build cylindrical cases of sand, but the most common grannoms in many larger streams make a four-sided, tapered case of vegetation that looks a little bit like a chimney. Facing upstream, the larvae firmly attach the front edge of their cases to submerged hard surfaces. Grannoms stretch out of their cases and use the long hairs on their hind legs to filter small food particles from the current. Once their legs are full of food, they bend one leg at a time to their mouths and eat the particles. This behavior has earned this and other families of caddis that display similar behaviors the name “peeking caddis,” after which a fly pattern was also named.

It makes sense that, on an individual level, gran-

noms are probably less likely to be available as trout prey than other nymphs because they are so firmly attached

Although the suggested pattern catches trout all year, it is most effective prior to mid-March, before larvae enclose themselves in their cases and pupate. The grannom caddis hatch usually continues from morning into the evening and is one of the most underappreciated hatches. For example, the number of grannoms that emerge on the Little Juniata River can be as impressive as the famous green drake emergence on Penns Creek, but there is one difference: the grannom emergence does not draw a huge fishing crowd.

22  |  common nymphs of eastern north america

to the bottom. This defense mechanism is great protection against their becoming a meal most of the time, but grannoms are so abundant in some streams that they end up in the drift frequently enough to be an important and vulnerable trout food. Although their cases may deter most other insect predators and some small fish, these types of cases do not keep trout from eating grannoms. Trout simply eat the whole caddis, case and all, and digest the nymph. fig. 15 American grannom caddis or apple caddis

fig. 16 Grannom caddis tied on a size 12 scud hook

Caddisflies  |  23

Case-Maker Caddisflies (Limnephilidae) up to 30 mm (1.2 inches)

More than three hundred known species of northern case-maker caddis exist in North America, many of which live in northeastern streams. Because caddis in this family generally prefer cool waters, they are more common at northern latitudes. Although ecologically important and occasionally abundant in eastern streams, limnephilid caddis are typically found in lakes, marshes, and slow-moving areas in streams, which is reflected by the Greek origin of their name—limne (lake) and phileo (love as a friend). Even so, if you are fishing a stream that supports trout year-round, it probably supports at least some of these caddis in backwaters, pools, or along stream margins. Because these caddis usually live in relatively stationary waters, they are climbers or clingers, which means they typically do not attach their cases to the substrate in the manner that grannoms and some other caddis do. Although these caddis may not be as common as drifting prey, they are an easy meal for fish because they are not very adept at reattaching themselves to the stream bottom once dislodged.

Depending on the species, limnephilid caddis vary

in size, color, and the type of case they build; nonetheless, most have cream, tan, or greenish bodies and build their cases out of mineral and vegetative materials. A few kinds, such as the genus Pycnopsyche, build large cases out of sticks and other vegetation—hence, the commonly used name “stick worm.” Larvae in this group are known as shredders, which means they usually feed on decaying plant matter. Their ability to shred leaves, bark, and other aquatic and terrestrial vegetation is very important to the proper functioning of stream ecosystems. Without shredders, the decay of organic matter would be dramatically delayed and lead to streamwide changes in terms of the structure of the food web.

Many limnephilid caddis emerge during midsum-

mer into the fall and their life cycle is related closely to the autumnal leaf fall. Delayed development of eggs or larvae in this family can allow them to bridge dry conditions that occur in many smaller streams. The eggs are

24  |  common nymphs of eastern north america

laid in a gelatinous mass, and after they hatch, the larvae remain in the mass until water again covers the eggs; consequently, the miniscule larvae can be protected by the jellylike substance for weeks or months. After leaving the mass, larvae initially feed on algae and then switch to feeding on the abundant leaf litter found in many forested streams during the fall. Feeding continues through winter, and then large larvae again enter an extended diapause (resting phase) by attaching their cases to the fig. 17 Case-maker caddis

fig. 18 “Giant stick worm” tied on a size 10 curved nymph hook to resemble limnephilids

Caddisflies  |  25

substrate. To pupate, the larvae seal their cases with silken plugs and transformation takes place for several weeks. Some common names of northern case-maker adults include dot-wing winter sedge, great cream sedge, silver-striped sedge, summer flyer sedge, and great brown autumn sedge.

Smokey Winged Sedges (Apataniidae) up to 11 mm (0.4 inch)

The majority of species in this family live in cold streams, but a few live in lakes. Although small, they can be very numerous in some streams and are important grazers of periphyton (algae attached to underwater surfaces). They are important prey for trout and other fish. To avoid predation, these caddis build cases using small pieces of stone and sand grains. Some species in this group also defend themselves by secreting a toxin from a gland located just behind their head that can paralyze insect predators (e.g., predaceous caddis larvae). This defense mechanism presumably has no effect on noninsect predators such as trout.

It may seem like a lot of work to make these flies with their sand cases, but it is actually very easy and probably faster than tying conventional nymphs, especially if you prepare the materials in bulk before you tie the remainder of the fly. When tied in a variety of colors and sizes, this nymph pattern imitates the Apataniidae, Odontoceridae, and Uenoidae families well. The best way to prepare the case material is to rinse it with a brass coffee filter or other very small screen and then let it dry for a couple of days. If you rinse a filter full, you will have enough material for thousands of flies. Another advantage of this pattern is that it is self-weighted and sinks like a rock or, more appropriately, a bunch of very small rocks. It is a thrifty and environmentally friendly alternative to using conventional lead wire or strips for weight. By using this pattern as the top fly while fishing multiple nymphs, you will not need as much, if any, weight to get the flies down to the bottom.

26  |  common nymphs of eastern north america

Dark Blue Sedges (Odontoceridae) up to 20 mm (0.8 inch)

Compared to many other caddis families, not very many species of odontocerid caddis exist (there are only twelve recognized North American species). The most common of these are in the genus Psilotreta and have dark heads, legs, and thoraxes and brilliantly green abdomens with small, branched gills along the sides. Psilotreta make fig. 19 Smokey winged sedges

fig. 20 Gravel-cased nymph tied on a size 14 hook

Caddisflies  |  27

incredibly strong, curved cases out of rock fragments arranged in a mosaic with their edges tightly aligned. Between the rocks is the “mortar,” which is made from silk and strengthened with small sand grains. These caddis need tough cases because they spend most of their larval lives burrowing through sand and gravel in riffles while eating algae, plant material, and whatever small animals they can subdue. During pupation, Psilotreta congregate in groups by the hundreds, often in slow-moving water along stream margins where they enclose themselves inside their hard rock cases. Pupae and adults are usually dark blackish with hints of green or olive.

Autumn Mottled Sedges (Uenoidae) up to 15 mm (0.6 inch)

These caddis are similar in appearance to limnephilid caddis, but they are often more abundant in many moderately degraded streams. Caddis in this family can be identified by the two or three perfectly balanced stones attached to the sides of their cases. The larger stones act as stabilizers to help keep the cases and larvae down in the riffles. Some species will group together fig. 21 Dark blue sedge

28  |  common nymphs of eastern north america

in the spring, attach their cases to the bottom of rocks, and enclose themselves in their cases by sealing the end with silk. They then spend the hot summer months as pupae in diapause. As previously mentioned, diapause is a period of inactivity common among aquatic insects in any stage before the adult. It is initiated to avoid adverse environmental conditions such as low flows or extreme temperatures. These caddis are present in most Pennsylvania trout streams because they live in a variety of habitats—from cold mountain streams to warm rivers in bottomlands. Because they emerge during the fall, these larvae can be available as trout prey after most mayflies and many caddis become less important as nymphs. The common name “sedge” is derived from the fact that, as adults, caddis spend much of their time clinging to streamside vegetation that is often composed of grasslike sedges.

fig. 22 Autumn mottled sedges

1

2

3

4

5

6

Mayflies (Ephemeroptera)

Relatively few described mayfly species (675) exist in North America, compared to other major groups of aquatic insects. Some mayfly species live in standing water, but the majority live in streams and rivers. In addition to being a large part of many fish, bird, and other animal diets, mayflies are important to scientists and conservationists because many species are indicative of good water quality. Just as trout need unpolluted water and high-quality habitat to survive and reproduce, most stream-dwelling mayflies need clean water and undisturbed habitat. When mayfly species disappear or become less abundant, scientists are alerted that problems such as chemical or physical pollution may be affecting the stream.

Mayfly nymphs can be distinguished from other

aquatic insects by the number (usually three) of caudal filaments (tails) and by the presence of gills on the tops or sides of most abdominal segments (fig. 23). Mayflies are often confused with stoneflies, but a good way to tell them apart is that stoneflies never have three caudal filaments, nor do they have gills on their middle abdominal segments. Some stoneflies, however, have gills on the underside of their first and second abdominal segments. Mayfly gills can be difficult to see when they are out of the water; therefore, counting caudal filaments is usually the quickest way to differentiate mayflies from stoneflies. Remember, though, that a few mayfly species (e.g., Quill Gordon, Epeorus sp.) have only two visible caudal filaments; the third filament is present but reduced to little more than a stub between the two long filaments. Mayfly families typically look different enough from one another that, with practice, you can identify them with-

30  |  common nymphs of eastern north america

Wing pads present

Abdominal gills

Three cerci (tails) One claw per leg

out magnification. A great help when identifying mayfly families is to consider the habitat where you found them; group-specific habitat is discussed in each section on the different mayfly families (and see appendix B).

Most mayfly nymphs are herbivores or detritivores,

which means they feed on algae, plants, or decaying organic material. Many mayfly species live in riffles where flyfishers commonly turn over rocks to try to match the nymph hatch. Riffle-dwelling mayflies are usually crawlers or clingers that inhabit the stream bottom as they search for food. Flatheaded mayflies (family Heptageniidae) have crablike bodies with a low, streamlined profile that helps them stay firmly on rocks in very swift current. Sulphur and hendrickson nymphs (family Ephemerellidae) can also live in swift currents, but they use their stout, strong legs to move among relatively protected areas in the small gaps of the substrate. A few mayfly families have body shapes and structures that allow them to be amazingly strong swimmers. For example, bluewinged olive nymphs (family Baetidae) are also known as small minnow mayflies because they use their long caudal filaments to help them dart over the substrate. Other swimming mayflies, such as those in the family Ameletidae, spend nearly all of their time in calm areas in pools fig. 23 Generalized mayfly characteristics shown on a little blue-winged olive (Baetidae) nymph

Mayflies  |  31

or along stream margins. Unlike caddisflies, mayflies are hemimetabolous, which means they do not have a pupal stage between the larva and adult. Mayfly larvae grow and mature by shedding their exoskeleton “skin” as they grow incrementally larger.

Developing adult wings are tightly packed inside

wing pads. Nymphs that are near emergence either crawl from the water or swim to the surface to emerge as subadults (subimagos). To emerge, the final mayfly skin separates along the middle of the back and the dun escapes. Like caddisflies, mayflies are most vulnerable to predation as emergers because they are still loosening their newly formed body parts. When trout are tail-splashing at what you may think are adults on the water surface, look closely in the surface film and you will likely see emerging mayflies. Some mayflies change immediately into the final adult stage (imago), but many other species spend time on streamside vegetation where the final body changes occur. Mayfly adults live for hours or days and lack functional mouth-

Wing pads become noticeable on large mayfly nymphs (fig. 24) and are often imitated by flytiers with turkey or goose feather fibers folded over the front portion (thorax) of the fly.

fig. 24 Well-developed wing pads on a late stage little blue-winged olive mayfly (Baetidae)

32  |  common nymphs of eastern north america

parts because their only goal as adults is to mate, which is usually accomplished in a matter of hours. Mating most often occurs in swarms, and once eggs are fertilized, females will typically fly above the water surface to lay eggs. Mayfly dry patterns often incorporate bright orange or green dubbing near their tails to imitate egg masses that the females carry. After depositing eggs, female mayflies expire on the water surface and induce the feeding frenzies of trout, usually near dusk and well after dark in some cases.

Little Blue-Winged Olives (Baetidae) up to 12 mm (0.5 inch)

Most flyfishers know baetid mayflies as “little bluewinged olives,” or “BWOs,” whereas scientists commonly refer to nymphs as small minnow mayflies. Baetids are probably much more abundant than you realize while turning over rocks, because they tend to dislodge and swim away when disturbed. Moreover, these mayflies are often most abundant in vegetation or algae beds in shallow eddies or runs. Many species in this family have two generations per year, which means there are two adult emergences during the warmer months—usually one early in the spring and one as autumn approaches. Unlike most other mayflies, female adults of some Baetis species crawl underwater to attach eggs to surfaces of stones and other structures. Many caddisfly adults demonstrate this behavior, but most mayflies drop their eggs at or near the water surface. Eggs typically remain dormant through winter months, and upon hatching, larvae rapidly grow to maturity. The transitional period from nymph to adult is very brief. After swimming to the water surface, emergers are vulnerable to feeding fish for only seconds before they fly away.

After catching one of these nymphs, put it in some

water in your hands or in a small, white tray and you will see how they got their name. To swim, these olive mayflies dart around by flexing their abdomens and tail filaments rapidly up and down like dolphins. Some people use a subtle, quick twitch of the wrist to impart a

Mayflies  |  33

swimming motion when fishing imitations of these small nymphs. It is difficult to say whether that method improves the appearance of the nymphs, but we are skeptical of the importance of imparting movement to nymphs, especially ones as small as baetids. Trout are very used to seeing drifting prey, and whether on the water surface or underwater, any unnatural movement or drag will deter all but the smallest (most inexperienced) trout from taking your fly. Although particularly apparent when fig. 25 Little blue-winged olive

fig. 26 Little blue-winged olive nymph tied on a size 20 nymph hook

34  |  common nymphs of eastern north america

fishing dry flies, the importance of a natural drift is also important when fishing nymphs. The obvious difference is that you see the denial of your fly less often when it is underwater.

Mayflies are usually indicators of good water qual-

ity, but several baetid mayfly species are exceptions to that rule. Some species need very clean, unpolluted water to survive, but others can inhabit rather degraded waters. An unfortunate but very good example of a stream with water quality issues and prolific BWO hatches is Spring Creek in Centre County, Pennsylvania. It may seem logical that tremendous abundance of one mayfly or other insect species would reflect good stream health, but the opposite is often true. A better indicator of stream ecosystem integrity is the number of different types (i.e., species) of organisms in combination with their abundance.

Mahogany Duns and Blue and Black Quills (Leptophlebiidae) up to 15 mm (0.6 inch)

Adult mayflies in the family Leptophlebiidae are known as slate mahogany duns, iron blue duns, blue quills, black quills, red quills, and quite a few other common names. As nymphs, they are normally called prong-gilled mayflies for the obvious reason shown in fig. 27. The early season blue quill hatches are most widely recognized, but in many eastern streams with good water quality, there are also midsummer prong-gilled mayfly hatches; thus, these nymphs are a useful pattern throughout much of the year in many streams. For example, Fishing Creek in Clinton County, Pennsylvania, will have sporadic hatches of size 18 blue quills from mid-June deep into September.

Prong-gilled mayflies are not well suited to swift

currents and usually live in protected areas such as leaf packs or filamentous algal beds. Dissolved oxygen concentrations are generally lower in slow water compared to riffles. These nymphs can live in relatively stagnant water in part because their large, featherlike gills have

Mayflies  |  35

more surface area to remove dissolved oxygen from the water. As omnivores, they typically eat algae and microscopic pieces of living or decaying vegetation, but they are known to ingest other small insect larvae and shed exoskeletons from other individuals, sometimes of their own species.

Out of water, the gills on these nymphs lie tightly

along their backs, but in flowing water, the gills pulsate in the current. fig. 27 Mahogany dun, blue and black quill

fig. 28 Dark quill nymph tied on a size 16 2X long nymph hook

36  |  common nymphs of eastern north america

The ostrich herl on the suggested pattern does an excellent job at mimicking the gills and, although not a critical component, it may increase its effectiveness. To imitate the gills, lay a strand of ostrich herl over the back of the abdomen and then rib it with heavy thread, wire, or tinsel to hold the herl down and extend the life of the nymph.

Flatheaded Mayflies (Heptageniidae) 5–20 mm (0.2–0.7 inch)

If you have ever turned over a rock and seen a flatheaded mayfly scurry away, you know how fast and agile they are. These mayflies appear similar to miniature blue crabs as they move because they are equally adept at crawling in any direction. Most flatheaded mayflies live in streams and rivers, but a few species live at the edges of lakes where wave action provides suitable dissolved oxygen concentrations. Their bodies and wide, flat heads are designed to help them hang onto and move over the stream bottom in some of the swiftest stream currents. Several flatheaded mayfly species have abdominal gills that are modified into suction cups that help them hang

fig. 29 Flatheaded mayfly (Heptageniidae) nymphs camouflaged against their surroundings

Mayflies  |  37

onto the stream bottom. If dislodged, however, they are very poor swimmers and can only wiggle desperately until they land on another rock; otherwise, they become an easy meal for waiting fish.

These mayflies are generally small (5–20 millimeters)

and live primarily on large rocks from which they scrape algae to eat. Their mouths are fitted with a large upper lip that deflects the swift current so that dislodged algae do not drift away. Interestingly, these mayflies demonstrate a behavior called positive thigmotaxis, which means they are always searching to be in contact with another surface. Given their poor swimming ability, it is no surprise that these mayflies always seek contact with the stream bottom. If several of these mayflies are put in a container, you can watch them cling to one another in a small, wriggling ball.

Quill Gordons, Pink Ladies, and Gray-Winged Summer Quills (Epeorus sp.) up to 12 mm (0.5 inch)

The namesake of the Quill Gordon dry fly pattern was Theodore Gordon, who designed it and fished the Catskills at the end of the nineteenth century. The mayfly species it was designed to imitate, Epeorus pleuralis, emerges early in the spring relative to most other famous hatches. These nymphs tend to be slightly smaller than other flatheaded mayflies and are often very abundant in forested headwater streams. This nymph is also one of the few mayflies that has only two (instead of three) visible tail filaments, which causes it to sometimes be mistaken for a stonefly.

During March and April, the suggested pattern often fools trout that apparently have no interest in more general patterns such as pheasant tails. When tying in moose mane or pheasant tail fibers for tails, do not be afraid to make them very long—at least twice the length of the hook shank if possible. This applies to all flatheaded mayflies. The long tails can be cumbersome in the box, but we think the tails’ underwater movement is worth the hassle.

38  |  common nymphs of eastern north america



The name “pink lady” comes from the fact that

adult females of the species Epeorus vitreus have remarkably bright pink abdomens. The pink hue results from the bright color of the females’ eggs shining through their translucent abdomens—hence the name. Although male and female E. vitreus adults have obviously different colorations due to the females’ eggs, the nymphs generally look identical to our naked eyes and probably to trout eyes as well. Because these species are generally fig. 30 Quill Gordon, pink lady, graywinged summer quill

fig. 31 Quill Gordon nymph tied on a 14 2X nymph hook

Mayflies  |  39

intolerant of sedimentation, they are more common in high-gradient, mountainous streams than they are in low-gradient, limestone streams. Nonetheless, this pattern works well in a variety of stream types and should be well stocked in fly boxes.

March Browns or Gray Foxes (Maccaffertium vicarium) up to 18 mm (0.7 inch)

The gray fox was once considered a different species (Stenonema fuscum) from the March brown, but they are now considered the same (Maccaffertium vicarium). Males are generally smaller (size 12 hook) than females (size 10 hook), but the same pattern in these sizes will imitate both sexes of the nymph. Some entomologists and anglers think these nymphs (and others in the family Heptageniidae) migrate from riffles toward stream edges before they emerge. It may be coincidental, but it often seems that trout take up positions near stream margins during the March brown emergence.

For these and most other mayflies, adults begin to struggle from their nymphal shucks (exoskeletons) before they reach the water surface. Typically, their folded wings are the first structures to emerge out of the exoskeleton because the shuck appears to unzip along the middle of the dorsal (top) surface. As a result, adding material that matches the color of the adult wings to the top of your nymph patterns can do wonders for their effectiveness during an emergence. Another tying trick is to add a patch of the adult body color to the nymph near the thorax and protruding wing to imitate the adult body beginning its escape from the shuck. These details may seem miniscule, but the way trout perceive their food is very different from the way we do. Try for yourself: fish one standard nymph pattern without adult wing and thorax coloration and one emerging nymph pattern in tandem, and trout will usually key on one or the other. The next day, finicky trout may be taking the other pattern, which is why you should include both types of flies in your box.

40  |  common nymphs of eastern north america



During May, be sure to look along stream edges for

trout and try these nymphs where you otherwise might not cast.

Cream and Light Cahills (Stenonema and Heptagenia) 5–20 mm (0.2–0.8 inch)

These flatheaded mayflies emerge at various times throughout the spring and summer and have several fig. 32 March brown or gray fox

fig. 33 March brown nymph on a 14 2X nymph hook

Mayflies  |  41

other ecological differences; nonetheless, they are similar enough in appearance that one pattern will do for flyfishers. The cahills are typically not as abundant as sulphurs, nor do they receive as much attention from anglers, but those are not necessarily bad things. Many readers may recognize the scientific name Stenonema and associate it with the March brown, gray fox, and a variety of other popular hatches. Taxonomy is ever changing. As new knowledge is gathered about the natural world, systematists and taxonomists rearrange and fig. 34 Cream light cahill

fig. 35 Emerging cahill on a size 14 nymph hook

42  |  common nymphs of eastern north america

reorganize the names of organisms to reflect what has been learned. Because scientists will continue discovering and describing new species, scientific names will continue to change. Although it can often be confusing to those of us who do not use the scientific names on a daily basis, they are a very important part of science because they reflect the perceived evolutionary relationships among all living things.

As anglers or flytiers, names are less important

than being able to imitate appearance and behavior that trout associate with a good meal. The pattern above (fig. 35) works well throughout the year, but a lighter, cream nymph does even better during cahill hatches.

Hendricksons, Red Quills, and Sulphurs (Ephemerellidae) 4–15 mm (0.2–0.6 inch)

Nymphs in the family Ephemerellidae are also known as spiny crawler mayflies because they spend the majority of their lives crawling among cracks and crevices in a variety of stream habitats. The “spiny” part of their name comes from the series of spines along the backs and sides of their abdominal segments. This spiny appearance, in combination with a scorpion-like posture, keeps predators at a distance when these nymphs are threatened. You can see this behavior if you put several of these nymphs together in a white tray. As they approach one another, they will often bring their tail filaments up over their backs and point them toward their aggressor. Although not much of a threat to trout, this stance is

To imitate the body shape of flatheaded mayfly nymphs, tie a piece of nonlead wire on each side of the front half of the hook. Taper-dub from the front back to the hook bend to create a flatter nymph that tumbles and wobbles through the riffles like the real thing. The pictured nymphs may seem rather bright while dry, but materials will typically darken as soon as they absorb water. Whenever you are experimenting with tying patterns for your favorite streams, tie flies with slightly lighter materials than the nymphs you find in the stream.

Mayflies  |  43

apparently intimidating to a similarly sized stonefly or other predaceous insect.

This family is very common in North American

streams and is quite diverse, with nearly twenty species in the most common genus, Ephemerella. Emergences that are particularly familiar to flyfishers, such as sulphurs, are Ephemerella species. Several other genera are more locally distributed and are usually not as abundant. One reason for the many different species in this family is that over eons, different species have been able to take advantage of a variety of stream conditions. Although they are not particularly streamlined or very strong swimmers, these nymphs are able to navigate their way through some of the swiftest stream currents by hanging on with their strong legs and staying in protected crevices between and under rocks. Other species prefer slower stream flows and do just as well crawling among vegetation, algae, and rocks in backwaters and pools. Regardless of their habitat, these nymphs are classified as either collectors or scrapers, which means they eat algae and microorganisms that are small enough for them to scrape from rocks or gather and ingest. fig. 36 Hendricksons, red quills, and sulphurs

44  |  common nymphs of eastern north america

hendricksons and red quills (Ephemerella subvaria)

Although two patterns imitate the male and female hendrickson adults (E. subvaria), one nymph pattern will do fine to imitate both sexes. Although adults of this species look different from sulphurs and emerge earlier, they are very similar in appearance, habitat, and behavior as nymphs. Hendrickson adults typically emerge earlier in the day than mayflies that emerge later in the summer. fig. 37 Hendrickson and red quill (Ephemerella subvaria) nymph pattern

fig. 38 Emergent sulphur nymph on a size 14 2X nymph hook

Mayflies  |  45

When stream temperatures warm to approximately 11°C (52°F), expect to see hendricksons and red quills emerge. Numerous patterns and color variations imitate emerging mayflies. sulphurs

The May and June sulphur hatches in many eastern streams are deservedly famous among flyfishers. Sulphurs are unnaturally abundant in some streams partly because several species tolerate marginal water and habitat quality. Sulphur hatch times overlap, but the smaller pale evening duns (E. dorothea) generally come later than the larger species (E. rotunda and E. invaria). Under close inspection, coloration of these nymphs can vary considerably, but on the whole, E. dorothea is usually a light tan compared to the other species, which are typically olive, brown, or nearly black in appearance.

Green and Yellow Drakes (Ephemeridae) 10–50 mm (0.4–2.0 inches)

Flyfishers do not marvel about many hatches like they do the Penns Creek green drake hatch in central Pennsylvania, and with good reason—the adults are large, beautiful, abundant, and an excellent trout meal. Nymphs in this family are not as obvious to us as those in some other groups, but they are certainly interesting in appearance and habit when we get the chance to see them. As nymphs, the drakes are very large, with modified forelegs, mouthparts, and heads that they use to burrow into sand, gravel, and silt. The nymphs make tunnels in the stream bottom with holes at both ends, and at night the nymphs come out of their burrows and ingest sediment that contains digestible organic material. Because these nymphs spend much of their time in burrows, they have

Often, simply adding a touch of the adult color to nymphs makes a world of difference as you dead-drift or swing your flies through the riffles.

46  |  common nymphs of eastern north america

The best time to use these patterns is during or just before the hatches. Otherwise, the only time these nymphs are available in significant numbers as trout prey is when they are scoured from their burrows by high stream flows. Despite their different adult appearance, nymphs of the genera Ephemera, Litobrancha (green drake and yellow drakes), and Hexagenia (slate drake) are very similar and the suggested pattern will do well for all three.

fig. 39 Green yellow drake

fig. 40 Green drake nymph tied on a size 8 curved nymph hook

Mayflies  |  47

very large, feathery gills to gather oxygen. By undulating their gills, these nymphs draw oxygen-rich water through their tunnels. When you consider how large these nymphs are compared to most other mayflies, it is not surprising that it usually takes two years for them to reach maturity. When they are mature, nymphs make their way to the water surface to make their final struggle into adulthood.

Slate Drakes or Great Leadwings (Isonychiidae) up to 14 mm (0.55 inch)

Isonychia, or brushlegged mayfly nymphs, live among vegetation, algal beds, and rock outcroppings in riffles and runs of many eastern streams. Although adults in this family have a common name (slate drake) similar to some more famous hatches, they are not in the same family as the other “drakes.” They are not as popular, either—possibly because they emerge later in the season, when fishing pressure has subsided. Despite the poor timing of the emergence for many flyfishers, slate drakes generate productive hatches and the nymph is an interesting and effective fly. Nymphs of this family fig. 41 Slate drake, great leadwings

48  |  common nymphs of eastern north america

are known as brushlegged mayflies due to the many fine hairs on their forelegs. While hanging onto the substrate with their middle and hind legs, these nymphs face the current and hold their brushy legs below their mouths. As fine food particles collect on their leg brushes, the nymphs eat diatoms, detritus, and algae. Although these nymphs are relatively strong swimmers, they spend most of their time hanging onto the substrate. These nymphs are one of the few types of mayflies that crawl out of the water to emerge. Before emerging, they migrate from riffles to calm areas along the stream margin, then crawl onto rocks and debris to shed their nymphal skin. This is when Isonychia nymphs generally work best because, as they move laterally to the stream edge, they often swim and drift downstream.

More so than with other mayfly patterns, mimicking a swimming action with a line twitch during the drift may entice trout to strike. If nothing else, it might give you a little more confidence while fishing.

fig. 42 Isonychia tied on a size 12–14 2X nymph hook

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Stoneflies (Plecoptera)

Stoneflies are not as diverse or typically as abundant as mayflies or caddisflies in large eastern trout streams. Like many mayflies and caddisflies, stoneflies generally require cold, clean water; consequently, most of the 626 known North American species live in mountainous streams. Some species are tolerant of relatively low pH (i.e., acidic) water. This is a necessity for living in small forested streams that often have moderately low pH as a result of decaying organic matter and geology that typically lacks the buffering capacity found in limestone streams.

Stonefly nymphs have many shapes, sizes, and

colors, but several characteristics can be used to differentiate them from other aquatic insects. Generally, stonefly nymphs are similar to mayfly nymphs in that both groups have long cerci (tails) and antennae, three pairs of conspicuous legs, and obvious wing pads on older nymphs. So, how can stonefly and mayfly nymphs be distinguished from each other? The common practice of counting tails to tell stonefly nymphs from mayflies usually works, but there are rare cases when it does not. This method usually works because all stoneflies have two candal (tail) filaments, whereas the majority of mayflies have three tail filaments. A problem is that a few types of common mayflies (e.g., some baetid and heptageniid nymphs) only have two visible tail filaments, which can cause them to be misidentified as stoneflies. The third filament is present on these mayflies, but it is extremely small and inconspicuous. Another problem is that nymph tail filaments of both groups are obviously small and fragile; consequently, the tails may be damaged or missing by the time we are straining to count them. The

50  |  common nymphs of eastern north america

Two claws on each leg

Two cerci (tails) Very long antennae Wing pads present

most reliable method for distinguishing between the two groups is to count the number of claws that a nymph has—stoneflies have two, whereas mayflies have one. Unfortunately, this method requires magnification or amazingly good eyesight. A more convenient and nearly as consistent method of identifying stoneflies is to look for abdominal gills. Stonefly nymphs never have gills on the middle or posterior (rear) portions of their abdomens, whereas all mayfly nymphs do. Some stoneflies have gills on the underside of their thoraxes and rarely the first three abdominal segments, but stonefly abdominal gills are not noticeable, compared to those of mayflies.

Five of the most commonly encountered stonefly

families are included here (and see appendix C). Several other families are no less beautiful, interesting, or important, but they are normally not encountered by the typical flyfisher. Additional resources are listed at the end of this guide if you want to learn more about these groups.

Many stonefly species are top predators in benthic

food chains; thus, they are regularly larger than other aquatic insects and often have longer life cycles. Because of their large size, big stoneflies (e.g., Pteronarcyidae) seem to be an irresistible meal for large trout. Stonefly nymphs periodically shed their exoskeletons. Interestfig. 43 Generalized stonefly characteristics shown on a common stonefly (Perlidae) nymph

Stoneflies  |  51

ingly, most of their growth occurs during cold months. Many stoneflies have one generation each year, but some species molt thirty-six times over three years before they reach maturity. Anglers often confuse small species of stoneflies, with mayflies. Identifying characteristics for the group are shown above (fig. 43); again, the easiest way to distinguish stoneflies from mayflies is that stoneflies have two caudal filaments instead of three.

More types of stoneflies exist in cold headwater

streams than in larger, warmer streams. Cold water can hold more dissolved oxygen than warm water; thus, part of the reason stoneflies are restricted to living in very cold streams is that they lack the extensive gill structures that most caddis and mayflies have. If stoneflies have gills, they are usually relatively small filaments found only on the thorax, rendering the stoneflies unable to absorb enough oxygen through their skin in warmer waters. Trout streams typically have sufficiently cold water to harbor several different species of stoneflies.

In headwaters, many types of stoneflies eat leaves

and other decaying organic matter, but the majority of “stones” that flyfishers encounter in valley streams are predaceous. During early instars (i.e., developmental stages), most stoneflies are either plant eaters or omnivores, but as mature nymphs, stoneflies are predators that hunt smaller invertebrates. Some species are opportunistic feeders, eating whatever is available, whereas others are selective and eat only specific prey. Predaceous stoneflies have very long antennae and amazingly large, fanglike lacina (i.e., mouthparts; see fig. 44) that they use to find, capture, and then engulf prey. Stoneflies also sense chemicals emitted by their prey or sense their movement through waves that they make in the water. Although nimble while holding onto rocks, stoneflies are typically very poor swimmers and are an easy meal for trout if they get caught in the drift.

Upon reaching maturity, stonefly nymphs crawl from

the water and rest on stones or vegetation to emerge as adults. In the same manner as mayfly nymphs, the final exoskeletal skin from which the adult emerges separates along the middle of the stonefly’s back (fig. 45). Although short lived, from only days to two weeks, stonefly adults

52  |  common nymphs of eastern north america

will eat algae and vegetation. Male adults make a drumming sound with their abdomens to attract mates as they crawl along streamside vegetation and rocks. The drumming patterns are species specific and are produced by the stoneflies’ beating their abdomens against the substrate or by vibrating them at very high frequencies. After finding a mate, male stoneflies fertilize the eggs, which develop and are then extruded onto the tip of the female abdomen. Females of most species deposit their eggs by dipping their abdomens as they fly across the water surface. fig. 44 Dorsal view of predaceous stonefly mouth showing fanglike lacina used to capture and eat other nymphs

fig. 45 Shed common stonefly exoskeletons

Stoneflies  |  53

As the eggs drift downstream, they settle to the bottom and stick to rocks individually or in gelatinous masses. Most of us know that trout and salmon eat fish eggs, but insect eggs can also be an important part of trout diets. We have observed trout feeding on insect eggs as they settled to the stream bottom, but it is unlikely that adult trout feed on eggs after they have adhered to the rocks. Stonefly eggs of several species are often loosely attached to one another and come apart shortly after entering the water. Some species have eggs that spend six months in diapause to avoid adverse conditions, whereas others hatch in less than four weeks.

Sallflies or Green Stoneflies (Chloroperlidae) 6–18 mm (0.2–0.7 inch)

Sallflies are sometimes referred to as green stoneflies because of their bright green coloration as adults. These nymphs are similar in size to perlodid stoneflies, but they lack distinctive patterns on their head, wing pads, and abdomen. This family is considered very sensitive to pollution; consequently, they are unfortunately not always

Chloroperlid stonefly nymphs have cerci that are shorter than their respective abdomens, unlike other stonefly nymphs, such as those in the family Perlodidae. It may seem like an unnoticeable difference when looking at a nymph pattern, but fish see and perceive things in a very different way from humans. Another characteristic of nearly all nymphs in this family is that they have relatively dark (e.g., brown) color patterns on a lighter background body color, usually yellow. To imitate chloroperlids, use yellow or cream thread and darker materials for dubbing and wing pads. These details may seem minor, but adult trout will have eaten tens of thousands of nymphs with specific appearances by the time flyfishers catch them. Prospecting nymphs will fool some fish—usually in the swiftest currents—but the more closely we can imitate overall nymph appearance, the more fish we will trick. The key is to balance realism with effort and cost while tying flies.

54  |  common nymphs of eastern north america

found in downstream portions of eastern trout streams. They are, however, in many headwater streams and some of the larger and more remote freestone streams throughout the East.

A few species in this family are collector-gatherers or

scrapers that eat algae and detritus; however, most sallfly nymphs are engulfer-predators that hunt for small insects and other organisms in gravel-bottomed areas with swift currents. Mouthparts of these and other predaceous insects have been replicated in science fiction and horror movies with good reason. The fanglike mouthparts of fig. 46 Sallfly or green stonefly

fig. 47 Green stonefly nymph tied on a size 14 curved nymph hook

Stoneflies  |  55

these predators are often sharply pointed and can also be serrated in multiple dimensions along the lacinal faces. After capturing their prey, predaceous stoneflies either engulf the whole organism, if it is small enough, or tear it into smaller, bite-size pieces. When scientists sample aquatic insect communities to study water quality, they are advised to preserve their collections quickly; otherwise, large predators such as stoneflies and hellgrammites can eat enough of the smaller organisms to change the outcome of the study.

Roachflies (Peltoperlidae) up to 15 mm (0.6 inch)

Roachflies acquired their name because of their similar appearance to the insects we sometimes unpleasantly encounter around the house. These stoneflies are very sensitive to human disturbances. If you see roachflies, you know the stream you are fishing is likely to be in very good condition. More so than other species of stoneflies, roachflies are not typically found in downstream, opencanopied portions of trout streams because the food they need is lacking. These stoneflies are not predaceous. Instead, they are classified as shredders because they do the important job of shredding leaves and other decaying organic matter found in streams. They can be very abundant and have been found to inhabit leaf packs in densities of more than five hundred individuals per square meter. Unlike many aquatic insects, some species in the family do not have an egg diapause stage. Instead, the eggs hatch very quickly during June or July and the nymphs begin to feed and grow. During the fall, large congregations of these nymphs often gather in temporary

Although they are uncommon in larger limestone trout streams, if you enjoy fishing small, forested trout streams throughout the East, you are also likely to find roachlike stoneflies, which can be a very productive pattern. Roachflies can crawl very quickly through leaves and other plant debris, but if caught in the current, they are poor swimmers and become an easy meal for trout.

56  |  common nymphs of eastern north america

streams where decaying leaf matter is abundant. Prior to their emergence in the spring, the nymphs move back to more permanent streams to complete their maturation.

Common Stoneflies or “the Stones” (Perlidae) 20–30 mm (0.8–1.2 inches)

These stoneflies are often simply called “the stones,” but their other name, common stoneflies, holds true because flyfishers see them more often than other stoneflies. Flyfishers encounter these species more frequently than smaller stoneflies, not because they are more abundant, fig. 48 Roachfly

fig. 49 Roachfly tied on a size 16 scud hook

Stoneflies  |  57

but because they are especially large and brightly colored. Some species and individuals can be mostly yellow as nymphs, but it seems that in larger streams, nymphs are often dark colored with yellow-highlighted areas.

Most species in this family are very sensitive to

chemical pollution and other human disturbances and are usually found in headwater streams. A few species are characterized as facultative, which means that they can live under a variety of different (often degraded) stream conditions. Part of the reason that some species are facultative is that they are opportunistic predators and will eat any organism they can catch. If you look closely at the mouthparts of these nymphs, it is rather fig. 50 Common stonefly

fig. 51 Common stonefly on a size 8 curved nymph hook

58  |  common nymphs of eastern north america

obvious that they are predators. Regardless of species, these nymphs cannot passively absorb enough dissolved oxygen out of standing water. If you put one into a tray of water, it will eventually do “push-ups” to circulate water and oxygen past the gills on its thorax. These bushy gills help them breathe in low-oxygen conditions and can be imitated by making a robust thorax, with dubbing guard hairs picked out.

Many trout streams have common stoneflies pres-

ent, but streams with good water quality typically have a greater abundance. If you flip over several rocks and

Of all nymph patterns available in most fly shops, it seems that many stonefly imitations bear the least resemblance to the naturals they are designed to represent. Although standard stonefly nymph patterns (e.g., Montana Stone) catch fish, they are usually not a very good color match and have undersized extremities, particularly antennae. Nymph coloration is different among families, species, and even populations (individuals of the same species in different streams). For example, perlid stoneflies in some streams resemble hornets, with brilliant yellow and black coloration, whereas closely related species in another nearby stream may be relatively drab brown. Use the photographs in this book as a general guide to the family colors, but for the best match, turn a rock or two in the streams where you fish and match colors according to the real nymphs. You will notice that perlid stonefly species have very long legs, cerci (tails), and antennae, relative to their body size. Moreover, when they are adrift, perlid stoneflies typically have their legs widely outstretched in a frantic attempt to grasp the substrate. Stonefly nymph patterns often underestimate these proportions and completely lack antennae, despite the fact that antennae are equally as apparent as cerci on the naturals. As suggested in the patterns included in this book, lacquered goose biots work well for stonefly appendages and are fairly durable. That being said, a variety of natural and synthetic materials with which to experiment are available, but be sure not to skimp on the length of stonefly legs, antennae, or tails.

Stoneflies  |  59

do not see any of these scurry away, they probably are not very abundant in the stream where you are fishing. If you can determine that common stoneflies are present in the stream you are fishing, they are often a good prospecting nymph if you are having trouble matching the nymph hatch.

Little Yellow Stoneflies (Perlodidae) up to 15 mm (0.6 inch)

Most flyfishers and flytiers are familiar with the adult pattern of many species in this family—the yellow sally. These nymphs are also known as stripetails and springflies. Although they are smaller than the previously discussed family (Perlidae), they are very similar in appearance. The easiest, most definitive way to identify stripetails from common stones is that stripetail nymphs lack the feathery gills that common stoneflies have on their thoraxes. Because they lack gills, stripetails need even colder, better oxygenated water than common stoneflies do.

Stripetails are predators as full-grown nymphs, but

they also eat algae during early stages of development. These nymphs typically hang onto boulders and cobble in large streams, but in headwater streams they are often fig. 52 Little yellow stonefly

60  |  common nymphs of eastern north america

found in leaf packs where the highest prey densities occur. These nymphs are opportunistic predators, but midge larvae are normally their most consumed prey. Many perlodid stoneflies undergo diapause as eggs to avoid warm water temperatures or dry conditions; some can stay in the egg stage for as long as seven months.

Even during early instars, these nymphs are some

of the fastest-crawling stoneflies and are nearly impossible to catch with your fingers. The best way to observe them is to rinse them into a white-bottomed container; otherwise, you will probably severely damage or kill the nymphs with your fingers.

Eastern Giant Stoneflies (Pteronarcyidae) up to 50 mm (2.0 inches)

If you have ever fished in the West, you probably know giant stoneflies as salmonflies. The name “salmonfly” comes from the importance of these nymphs and their emerging adults to the diet of western salmon and trout. Because trout are much more common than salmon in the East, it is probably more appropriate to call them giant stoneflies here. Although this family occurs primarily in small- to medium-sized streams, we have found them fig. 53 Sally stonefly tied on a size 14 2X nymph hook

Stoneflies  |  61

living in rivers where leaves and detritus accumulate under large stones and in backwater eddies. Giant stoneflies are able to live in larger streams partly because they have additional gills on their abdominal segments that most stonefly families do not have. These gills help giant stoneflies acquire oxygen that may be in relatively short supply in warm water.

Leaves are the mainstay of their diet, but these

nymphs are so large that they do not hesitate to eat smaller invertebrates when they find them. Although intimidating to other insects, giant stonefly nymphs will immediately curl into balls and pretend to be dead if you pick them up. By curling up, the gills and relatively fragile underside of the nymph are better protected from fig. 54 Eastern giant stonefly

fig. 55 Giant stonefly tied on a size 8 curved nymph hook

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crayfish and other predators; these nymphs have plates on their backs that are surprisingly rigid and are probably very difficult to handle and penetrate for most aquatic predators. Although giant stonefly adults are not nearly as important to anglers in the East as they are in the West, these nymph patterns can be effective along the banks as nymphs migrate to emerge, particularly at night or early morning.

Giant stonefly patterns are almost always productive in eastern headwater streams, particularly when fishing for brook trout. Stoneflies, giant and otherwise, are generally not important prey for trout in limestone streams that support an abundance of aquatic vegetation, scuds, sowbugs, and midges. Although some stonefly species inhabit limestone streams, they usually constitute a relatively low proportion of potential trout prey; consequently, these patterns do not seem to be as effective in “chalk” streams. Big stonefly patterns are most effective in large, forested streams and rivers with an abundance of small boulders; moreover, they are particularly effective under certain conditions. An important fact to remember is that stoneflies leave the water to complete their transformation into adults. Consequently, stoneflies are not going to be available to trout as emergers, but stonefly nymph patterns are likely to be more productive when nymphs are migrating to the banks prior to their emergence. Large and dark stonefly nymphs also work well after rain, which causes streams to be elevated and murky, because (1) higher stream flows dislodge otherwise unavailable stonefly nymphs and (2) trout are more likely to see their large silhouettes in colored water. Similarly, stonefly patterns are most effective on a day-to-day basis when it is dark outside. This has everything to do with trout behavior, which in turn is related to nymph behavior. Dragonflies, mayflies, and stoneflies are some of the oldest living members of the Pterygota subclass (winged insects) and are thought to have originated more than three hundred million years ago. Aquatic invertebrates and the predators (e.g., trout) that feed on them have coexisted for millions of years because they coevolved behavioral

Stoneflies  |  63

and physiological attributes that keep their populations in balance. For example, trout and other drift feeders locate their prey primarily by sight, which requires at least some light. It is theorized that insects drift more at night to reduce the chance of being seen and subsequently eaten by predators; consequently, the closer or more similar it is to night (i.e., overcast skies), the more insects drift and the more trout feed. The informed flyfisher can take full advantage of this amazing and predictable relationship. Early birds get the worms, and so do early trout.

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True Flies (Diptera)

The scientific name of the order Diptera originates from two Greek words, di (meaning twice or double) and ptera (meaning wings), reflecting the fact that adults in this group have two wings, whereas most other insect adults have four wings. Diptera is an incredibly diverse group, with only one insect order consisting of more species (Coleoptera, beetles). Not all true flies have aquatic larvae, but larvae of most species require at least moist living conditions (e.g., wet soil or leaf packs). Most people are familiar with many terrestrial true flies, including house flies and mosquitoes. Globally, nearly one hundred twenty thousand described species of true flies exist— seventeen thousand species occur in North America—but not all are aquatic. This order does, however, have more species among its aquatic representatives than any other insect order, even those that are wholly aquatic (e.g., mayflies and stoneflies).

Generalizing about true fly larvae is very difficult

because of the amazing adaptations displayed by the thousands of North American species in this group. Some border on being microscopic and are relatively nondescript, whereas others can be hairy, quite large (nearly 10 centimeters), and resemble something from a monster movie. There seem to be as many colors as species in this group, from simple shades of white and green, to brilliant reds and yellows, to the deepest, darkest black. Many species are translucent or even transparent. In some large and “see-through” crane flies, you can sometimes see remnants of midges or other small invertebrates as they move through the gut.

Perhaps the most straightforward way to remember

the general appearance of true flies is to think of their

True Flies  |  65

terrestrial cousins, maggots. Like maggots, aquatic true flies can be characterized as being worm- or grublike. True fly larvae typically have cylindrical and soft bodies (without obviously hard exoskeletons) and lack wing pads. Although some species have structures that look like legs (e.g., prolegs or creeping welts), they do not have segmented legs like those of many other insects (fig. 56). Many kinds of dipterans (such as black flies and midges) have noticeable, hard head capsules, but many other species (crane flies, for example) appear to lack heads and seem more like worms than insects. In these groups, the head is there, but it is retracted inside the skin and cannot be seen unless the larva extends it outward in selfdefense or in pursuit of prey. The range of larval sizes among species in this group is substantial and can be from less than 2 millimeters (e.g., some midges) in length to as long as 100 millimeters (e.g., some crane flies).

Any temporary or permanent water, or even moist

soil, is likely to have dipterans living in it. A few broad divisions classify habitat types of aquatic dipterans. The first difference is whether they live in flowing (lotic) or standing (lentic) water. For those in standing-water habitats, another division is whether they are in aquatic or semi-aquatic (e.g., wet soil) habitats. The amazing range of aquatic habitats that harbor dipterans includes virtually all streams and rivers, geothermal hot springs and geysers such as those found in Yellowstone, natural seeps of crude oil, puddles in tree stumps and other plants, alkaline seeps, and the Great Salt Lake, where few other organisms can survive. Throughout the East, where coal mining has affected many streams with acidic and otherwise toxic discharges (e.g., heavy metals), some dipterans can inhabit streams that have pH as low as 2.0. As a point of reference, hydrochloric acid has a pH of 2.0. As you can probably guess, any trout stream you fish will have a variety of dipterans living in it as well.

Most true flies that live in streams are clingers or

burrowers; consequently, many species have structures that are termed prolegs or creeping welts. Prolegs are structures that look like legs and serve a similar purpose, which is to grasp the substrate. Creeping welts are “swollen” areas along the length of some larvae that help them

66  |  common nymphs of eastern north america

burrow into mud and other soft sediments. Dipterans have a variety of feeding habits. Some are shredders or collectors that search through the sediment and detritus for edible organic matter. Other groups are efficient predators that eat other invertebrates using piercing, spearlike or, more typical, grasping, tearing, and chewing mouthparts. Although various adaptations allow different species to breathe in many kinds of habitats, most dipterans take in oxygen directly through their skin.

The life cycles of dipterans are as varied as their

habitats and feeding behaviors. Many species have one generation per year, but in southern climates, some mosquito species have as many as twenty generations each year. The opposite is true in northern climates; one chironomid midge species takes seven years to complete one generation because the ponds in which it lives remain frozen for most of the year. Most dipterans that live in trout streams have at least one generation per year. The larval stage of most true flies lasts from weeks up to two years and they remain active throughout the year, which makes them particularly available to trout during the winter (see appendix D). The pupal stage of dipterans is short and lasts from only days to weeks; furthermore, unlike caddisflies, dipterans rarely fig. 56 Crane fly larva of the genus Hexatoma

True Flies  |  67

build structures in which to pupate. Many dipteran species pupate in the same areas where they live as larvae, but some either crawl out of the water or move to wet sand or gravel along the stream margins. When pupation is complete, most species float to the surface using an air bubble that has formed under the pupal skin. As adults emerge, they use the pupal shuck as a raft on which to float while they dry and stretch their wings and legs. Adult dipterans usually live less than two weeks and feed on fluids. Most dipteran adults have piercing mouthparts, and depending on the species, they will feed on fluids from living plants, decaying matter, or in many cases (e.g., mosquitoes and deer flies) the blood of vertebrates. Mating of many aquatic dipterans occurs in swarms, and the females then lay the eggs before dying and becoming a small but abundant meal for trout and other fish.

Midges (Chironomidae) up to 30 mm (1.2 inches)

More than two thousand species of chironomid midges are known to exist, which makes this the most diverse family of aquatic insects by far. These larvae are found in all types of standing and flowing water and are an exceptionally important component of aquatic food chains. Their massive numbers compensate for their small size. By eating algae, and in turn being eaten by invertebrates, fishes, and other vertebrates, they form a critical link between the bottom and top of food chains.

Different midge species can be found nearly every-

where throughout streams. Some midges roam freely, but many species make tubular cases of silt and small pieces of organic matter. The tubes are often built in the silt, but some species build their cases on rocks, vegetation, and even on other organisms. Most midge larvae are grazers that feed on organic matter in the silt, but some are filterfeeders that build nets to filter water and food through their cases. Most free-roaming midges are predaceous and eat smaller midges, worms, and microorganisms.

68  |  common nymphs of eastern north america



Midge pupae develop quickly, then float and swim to

the water surface to emerge. Like mayflies, midge adults are short lived and do not feed. Larval coloration is quite variable among species and can be cream, yellow, green, bright red, and a variety of colors in between. Red midge larvae are red because of a hemoglobin-like pigment that retains oxygen. These “blood worms” can live in especially degraded environments that have low dissolved oxygen concentrations.

fig. 57 Midges

fig. 58 Assorted midge patterns tied on size 18–22 hooks

True Flies  |  69

The next time you are fishing downstream from a fish hatchery or wastewater treatment plant, which are sometimes located on some of the most productive eastern trout streams, try a red midge pattern because they are likely to be abundant.



All streams that have suitable fish habitat will harbor

midges. Midge emergences occur throughout the year and can provide incredible winter fishing, both with dry and subsurface flies. Generally, the poorer the water quality of the stream you are fishing, the more important midge patterns will be relative to other groups, such as stoneflies. Another place to try midge patterns is in heavily fished streams. Spring Creek in Centre County, Pennsylvania, is very heavily fished in some sections. Often, fishing a midge pattern will catch fish from riffles where others have fished pheasant tails or hare’s ear nymphs all day with little success.

Black Flies (Simuliidae) up to 15 mm (0.6 inch)

Black flies live in all sizes and types of streams and rivers but never in standing water. Black flies attach themselves to rocks, logs, and other debris with sticky silk secreted from their mouths. After making a silk pad on the substrate, these larvae hang onto their pads with minute hooks on the ends of their abdomens. As larvae move away from the pads, they attach silk threads in case they lose their grip on the substrate. Black flies are filter-feeders and have fan-shaped sieves just above their mouths (fig. 61) that they protrude into the current. The larvae periodically sweep the suspended fine food particles from the fans into their mouths.

Black fly pupae are one of the few dipterans to build

protective pupal cases, which are hard capsules that they weave with silk and attach to the substrate. The pupae take in oxygen by using two branched gills that extend out of the cocoon. Black fly adults emerge while still

70  |  common nymphs of eastern north america

in the cocoon, and as they depart, an air bubble forms around them that helps them float to the surface. Anglers, or anyone who spends time near flowing water, are unhappily aware of female black fly adults that need a blood meal for their eggs to mature properly. Similar to nonbiting midges (Chironomidae), black flies usually have multiple generations each year and adults typically emerge during the spring and summer. Black fly adults emerge during the warmer months, but their larvae are available to trout throughout the year. Black flies are found in nearly all flowing waters, but they are usually most abundant in those enriched by waste-treatment facilities, livestock operations, and malfunctioning septic systems. Ironically, fig. 59 Black flies

fig. 60 Black fly tied on a size 16 scud hook

True Flies  |  71

insecticides are sometimes applied directly to alreadypolluted streams to control the number of biting adults. If we could restore water quality in those streams, black flies probably would not be much of a nuisance outside of their natural habitats (i.e., large rivers).

Black flies acquired their name because of their

dark-colored adults, but the larvae are usually a shade of olive or brown. The larvae have a unique shape and are much stouter than chironomid midges.

Crane Flies (Tipulidae) 3–100 mm (0.1–3.4 inches)

Crane flies are the largest family of true flies, with nearly six hundred North American species. The habitats of the different species are also quite varied—from trout stream riffles, acidic bogs, moist soils and algal accumulations, and decaying vegetation, to salty intertidal zones and

To tie these flies, build their body shape by wrapping thread or floss and apply a generous amount of head cement or epoxy. Add ribbing to accentuate their segmented bodies and to extend the life of the fly.

fig. 61 Black fly larva labral fan used to filter suspended food particles from flowing water

72  |  common nymphs of eastern north america

marshes. Tipulid larvae are usually shredders that eat decaying plant material, but some species are engulferpredators (fig. 64). Most crane fly larvae have similar, grublike bodies, but there are many different colors and sizes. To identify different genera and species, you need to look at very small characteristics—often, breathing structures termed spiracles. Generally speaking, tipulids are cylindrical with retracted heads that are concealed within their thoracic skin. Some species are very large, but others are very small. In small, forested streams where leaf packs are abundant, several very large crane fly species are common, and from a distance the adult

fig. 62 Crane fly (Antocha)

fig. 63 Mini cream crane fly (Antocha) tied on a size 16 scud hook

True Flies  |  73

stage looks like an enormous mosquito. Crane fly adults do not eat blood and most are thought to feed exclusively on plant nectar. Many crane fly species that typically occur in trout streams are much smaller; the adults look somewhat like large midges. Because this is such a diverse family, it is impossible to make generalizations regarding the type of streams in which individual species occur. Some species require very clean water, while others are tolerant of different types of pollution.

Horse Flies and Deer Flies (Tabanidae) 11–60 mm (0.4–2.4 inches)

Many people who spend time near open water are painfully aware of horse fly and deer fly bites, which often draw blood and can produce large and itchy welts. As larvae, they have vicious mouthparts—similar to those they have as adults. Luckily, flyfishers and other vertebrates are safe from larval tabanid bites because these species feed only on invertebrates as larvae. The wormlike larvae have very rigid, spearlike mouthparts that they use to slash large holes in their prey. They then insert their heads into the body cavity and eat the prey from the inside out. Larval size varies among species, but shape

fig. 64 Hexatoma sp. crane fly eating mayfly nymph

74  |  common nymphs of eastern north america

and coloration within this group do not. Generally, horse flies and deer flies look similar to how a stretched football might appear. They are tapered on both ends and are usually cream, tan, or brown. A major difference between some dipterans (including this group) and many other aquatic insects (e.g., mayflies) is that many dipteran species do not lay eggs directly in water. They often lay eggs on or inside vegetation that is hanging over water or moist soil. After hatching, larvae fall into the water to feed and grow until pupation. fig. 65 Horse flies and deer flies

fig. 66 Horse fly tied on a size 14 2X nymph hook

True Flies  |  75

During spring and early summer, be sure to have the suggested pattern in cream, gray, and brown from sizes 10 through 16. After you have been harassed by adult horse or deer flies during the fishing season, imitating their larvae becomes less effective for catching trout.

Snipe Flies (Athericidae) 10–20 mm (0.4–0.8 inch)

Few flyfishers know what snipe flies are—probably because they are not likely to be a very important part of trout diets as pupae and adults, because they migrate from the water as mature larvae to spend their pupal and adult stages on land. As larvae, snipe flies are widespread and can be very abundant in some streams. In addition to having unique life history characteristics, they are also different from many dipterans in terms of their habitat and appearance. By possessing specialized structures, larvae are able to live in very swift currents. Like all dipteran larvae, snipe flies do not have segmented legs; instead, they have a series of prolegs along their undersides. fig. 67 Water snipe flies

76  |  common nymphs of eastern north america

Prolegs are similar to segmented legs, but they are simple, fleshy bulges that have small hooks at the end. These hooks are incredibly well suited for grasping edges on stones that look as smooth as marbles to humans. While we have observed these piercer-predator larvae feeding on very large, soft-bodied crane flies, they usually feed on smaller insects, such as midges.

When imitating these larvae, tie patterns similar to other dipterans, but include materials that move in the water. Not only do the prolegs and tail-like anal filaments give them a bushy appearance, but they flex and spiral more than most other aquatic insects as they desperately try to regain their grip on the substrate.

fig. 67 Snipe fly tied on a size 12 nymph hook

1

2

3

4

5

6

Hellgrammites and Other Aquatic Arthropods

Hellgrammites (Corydalidae and Sialidae) up to 90 mm (3.6 inches)

Hellgrammites are the larvae of dobsonflies (Corydalidae) and alderflies (Sialidae). These insects have a pupal stage, which means they undergo complete metamorphosis. Unlike caddisflies, which lay their eggs and pupate under water, hellgrammites are aquatic only as nymphs. Most species spend at least two years as nymphs, and then crawl out of the water to pupate and emerge as adults. We rarely see the adults, except when they are attracted to porch or street lights, because they typically only live long enough to lay their eggs on streamside objects.

Dobsonfly and alderfly nymphs are similar in ap-

pearance to caddisflies—in that they have soft, fleshy abdomens and segmented legs that extend from their thoracic segments. Aside from those few similarities to caddisflies, nymphs in these groups are unmistakable, particularly when they grow to large sizes (as long as 9 centimeters, or 3.6 inches). Hellgrammites are usually dark brown or nearly black, have strongly flattened bodies, and are fringed with fleshy filaments protruding from their abdominal segments. These predacious nymphs have powerful and serrated mouthparts, stout legs, and grasping anal claws. This imposing appearance was the inspiration for a 1960s comic-book supervillain—a mad scientist who somehow crossed himself with an insect and subsequently terrorized the public by trapping his captives in silk cocoons.

These insects have structures that allow some

species to live in particularly harsh conditions, such as waters with low dissolved oxygen or low pH. Some hell-

78  |  common nymphs of eastern north america

grammite species live in large rivers partly because they can absorb oxygen through their soft abdominal skin and abdominal appendages. To breathe more easily in warm waters, which typically hold lower oxygen concentrations, hellgrammites in the genus Corydalus have muscular gill tufts at the bases of their abdominal appendages. Some species use long breathing tubes that extend from the posterior end of their abdomens to obtain scarce oxygen. You can probably guess by their large size and substantial mouthparts that these nymphs are at the top fig. 69 Hellgrammite

fig. 70 Hellgrammite tied on a size 8 curved nymph hook

Hellgrammites and Other Arthropods  |  79

of the invertebrate food chain in streams. Be careful if you handle them—large ones can easily break the skin with their large mandibles or claws. Hellgrammites can be found throughout streams, but they prefer to hunt in the swiftest currents. Although their strong claws usually have a good grip on the stream bottom, these nymphs are fairly good swimmers if they become dislodged.

Alderflies (Sialidae) are similar in appearance and

biology to hellgrammites and occur in most Pennsylvania streams, but they are typically smaller (10–25 mm). The next time you fish big, downstream sections of large streams and rivers such Penns Creek, the Little Juniata River, and the Delaware River, give a hellgrammite pattern a try (see appendix E). The suggested pattern works particularly well in small sizes while dead-drifting for trout, but large, dark hellgrammites tied with soft materials (e.g., marabou or rabbit strips) and retrieved with short strips also imitate dislodged and swimming hellgrammites.

Sowbugs (Asellidae) up to 20 mm (0.8 inch)

Although they are called sowbugs or cress bugs, these organisms are not insects. As crustaceans in the order Isopoda, they are more similar to lobsters and crabs than they are to insects. Their common names are based on two characteristics: (1) they carry their young on a thoracic structure that makes them look like a sow (female pig) with young and (2) they are often abundant in cress beds, which can make them a pest where cress is grown commercially.

Despite living in an assortment of standing and

flowing waters, sowbugs rarely live in water more than 1 meter (3 feet) deep. Although they can be found in freestone streams, sowbugs are most abundant in limestone streams that are fed by alkaline springs. Most of the time, sowbugs can be found under rocks and among vegetation because they avoid light. Sowbugs are omnivorous and eat whatever they can find and digest. To breathe, sowbugs absorb dissolved oxygen from the water through

80  |  common nymphs of eastern north america

thin, platelike gills at the bases of their abdominal appendages.

Sowbugs can grow to be quite large in some streams,

but they are usually similar to size 14 or 16 hooks. Their undersides are almost always a creamy color, but their shellbacks can be gray, brown, or nearly black. This color pattern—light on the bottom and darker on the top—is called countershading and is present on many invertebrate and vertebrate animals. If viewed from above, they blend in with the stream bottom; from below, they fade fig. 71 Sowbug (ventral view)

fig. 72 Sowbug (dorsal view)

Hellgrammites and Other Arthropods  |  81

into the light-colored surface waters above. Countershading does little to save drifting sowbugs from trout because they are very poor swimmers and can only attempt to latch onto the substrate, algae, or vegetation. As with many nymph patterns, tying exaggerated legs on this pattern imparts movement. This little bit of extra undulation in the water may help fool wary trout, particularly in slow-moving pools and runs where the fish have more time to inspect their prey.

Scuds (Gammaridae) 5–20 mm (0.2–0.8 inch)

Scuds rarely swim, but when they are threatened, they can swim very well if they roll over on their sides. That behavior is why these small crustaceans are also known as sideswimmers. Scuds live in many different types of aquatic habitats, including hot springs, large river backwaters, small temporary ponds, and, of course, trout streams.

Because they are prey for other animals, scuds and

many small invertebrates exhibit “negative phototaxis,” which means they immediately head for cover if they fig. 73 Gray sowbug tied on a size 16 nymph hook

82  |  common nymphs of eastern north america

sense light. As you might expect based on that fact, scuds are nocturnal. In seeps and caves where sunlight is minimal or absent, some scud species have greatly reduced eyes or do not have eyes at all. Regardless of where they live, scuds are omnivores that feed on detritus particles and decaying animal matter. When available, scuds will also eat algae and plant material and will occasionally attack smaller invertebrates. Scuds eat large food particles by holding them with their front claws while they chew; otherwise, they graze as they crawl. To breathe, fig. 74 Scuds

fig. 75 Amber scud on size 16 scud hook

Hellgrammites and Other Arthropods  |  83

scuds have small gills similar to those of sowbugs near the bases of their appendages.

Most scuds found in eastern trout streams are gray,

brown, or olive colored, but they sometimes are vibrant shades of blue, red, and purple. Although diet is partly responsible for body coloration in scuds (and many other aquatic invertebrates), genetics have been found to be the primary influence. Because the fittest survive, scuds that blend in the best are not eaten and pass on their “camouflage genes” to their offspring. Aside from size and color variations, different species and populations of scuds are generally similar in appearance. Scuds are crescent shaped and strongly compressed laterally (from side to side), and all species have either fifteen or sixteen visible body segments. Appendages, including seven pairs of legs, extend from the ventral (bottom) side of scuds, which enable them to crawl, swim, and feed. As with sowbugs and other nymph patterns, do not hesitate to exaggerate the number and length of scud legs. Scud legs on the suggested pattern are a simple and effective imitation—picked-out dubbing has a translucent appearance and the coarse guard hairs simulate legs nicely.

Crayfish (Cambaridae) 10–150 mm (0.5–6.0 inches)

Crayfish are in the order Decapoda, which means that they have ten (deca) walking feet (poda). They all have the same basic body plan but are a relatively diverse group with more than 315 known North American species. Crayfish gills must remain moist for them to survive, but that is the primary natural limitation to where they can be found. In streams, they usually live in water less than 2 meters (6 feet) deep. Crayfish are nocturnal and typically stay hidden in burrows or under rocks and logs during the day.

As omnivores, crayfish will eat anything they can

find as they crawl among boulders, tree roots, and silt— usually during the night. In addition to defense, their large, powerful pincers are used to crush snail shells and capture other prey. They use their subsequent pairs of

84  |  common nymphs of eastern north america

legs to chop and handle food or scrape algae from rocks before ingesting it. Because they are relatively large and can eat a variety of food types, crayfish are usually very important to stream and lake communities. Not only do crayfish help determine the abundance of plant material and other organisms in streams but they also influence the presence or absence of other organisms; consequently, they have been deemed “ecosystem engineers” because of their burrow-building and ability to break down organic material rapidly. Some crayfish species grow to fig. 76 Crayfish

fig. 77 Crayfish tied on a size 6 curved nymph hook

Hellgrammites and Other Arthropods  |  85

large sizes and are particularly aggressive, causing them to disrupt ecosystems if they are introduced to areas where they are not native. The rusty crayfish (Orconectes rusticus) has been widely introduced and has caused a variety of ecological problems, including displacing native crayfish and reducing the abundance and variety of plants, invertebrates, and fish. Although some crayfish introductions have been attributed to the commercial harvest of crayfish for food, most crayfish introductions are likely from their use as live bait. If tied and fished properly, crayfish imitations can be nearly as effective as the real thing, which eliminates the possibility of spreading potentially harmful nonnative species.

The most famous crayfish flies were developed for smallmouth bass fishing, but in smaller versions, these patterns can be very effective for trout. When trout (particularly brown trout) grow to large sizes, they eat food items that contain more energy than the typical aquatic insect diet to continue growing. Using the common deaddrift approach with crayfish patterns works well, but make sure the fly is bouncing right along the bottom. Twitching your rod tip during the drift can induce strikes because it imitates the short, backward bursts of a fleeing crayfish. Another thing to keep in mind is that crayfish and large predatory fish (e.g., bass and trout) are nocturnal and most active at night. If you enjoy night fishing, bounce a big crayfish pattern with lots of motion past an undercut bank in your favorite trout stream or bass river. You may not catch as many fish using crayfish patterns as you would with other nymphs, but the few, big fish you catch will make it worth your while.

family

Hydropsychidae

Philopotamidae

Rhyacophilidae

Brachycentridae

Limnephilidae

Apataniidae

Odontoceridae

Uenoidae

common name

Netspinner caddis

Little black caddis

Green caddis

Grannom caddis

Case-maker caddis

Smokey winged sedge

Dark blue sedge

Autumn mottled sedge

Common

Common

Common

Common

Common

Very common

Very common

Very common

occurrence

High

Moderate

Moderate

Moderate

Very high

High

High

Very high

abundance

Riffles and runs, cobble and gravel

Runs and pools, various substrate

Riffles and runs, various substrate

Pools, various substrate

Runs and pools, various substrate

Riffles, cobble and gravel

Runs, various substrate

Riffles and runs, various substrate

typical habitat

Caddisfly availability to trout, habitat, typical emergence, and usual maximum body length

a ppen dix a : c ad di sfly attr ibutes and simple fly patterns

September through October

Mid-May through early July

Early April through mid-May

June through October

Mid-April through mid-May

Late April through mid-July

Late March through mid-May

April through October

emergence period

15 mm (0.6 inch)

20 mm (0.8 inch)

11 mm (0.4 inch)

30 mm (1.2 inches)

11 mm (0.4 inch)

30 mm (1.2 inches)

17 mm (0.5 inch)

30 mm (1.2 inches)

max. body length

family

Hydropsychidae

Philopotamidae

Rhyacophilidae

Brachycentridae

Limnephilidae

common name

Netspinner caddis

Little black caddis

Green caddis

Grannom caddis

Case-maker caddis

10–16 nymph

14–16 nymph, 12 scud

14–16 2X nymph

14–18 scud, 2X nymph

12–18 scud

hook

Brown

Black

Brown

Brown

Brown

thread

Simple fly patterns designed to imitate common caddisfly larvae abdomen/case

—

—

Ginger soft hackle fibers

—

Dubbed, dark brown

thorax

Cream dubbing “peeking” from Dubbed, tan or brown case, which is wrapped ostrich herl with ends twisted and tied off to imitate sticks

Green dubbing “peeking” from — case, which is two pieces of twistable lead-free weight, cut on a taper, tied on each side of the hook; wrap three strands of stripped peacock herl toward the hook eye and coat with lacquer

Bright green dubbing, plastic strip Dubbed, green back, ribbed with fine wire

Yellow dubbing, plastic strip back, Dubbed, orangeribbed with fine tinsel brown

Brown or gray down Tan, brown, olive, or mixed dubfibers bing, plastic strip back, ribbed with fine copper wire

anal claw (“tail”)

Wrapped starling hackle

Wrapped starling hackle

Ginger soft hackle or pheasant tail fibers

Ginger soft hackle fibers

Ostrich herl

legs

88  |  appendix a

Apataniidae

Odontoceridae

Uenoidae

Smokey winged sedge

Dark blue sedge

Autumn mottled sedge

14–16 nymph

14–16 nymph

16–18 nymph

Brown

Black

Brown

Simple fly patterns designed to imitate common caddisfly larvae (cont.)

—

—

—

Same as case-maker caddis (above) with cream “peeking” abdominal segment

Same as case-maker caddis (above) with bright green “peeking” abdominal segment

Cream or green dubbing “peeking” from case, which is thread wrapped to form shape, coated with lacquer, and then sand and gravel

Wrapped starling hackle

Wrapped starling hackle Wrapped starling hackle

Dubbed, dark brown

Dubbed, bright green Dubbed, dark brown

Appendix A  |  89

Common

Very common

Leptophlebiidae

Heptageniidae

Epeorus sp.

Maccaffertium vicarium

Stenonema and Heptagenia

Blue quills, black quills, little mahogany duns

Flatheaded mayflies

Quill Gordon, pink lady, and gray-winged summer quills

March brown/gray fox

Cream and light cahills

Common

Very common

Common

Very common

Baetidae

Little blue-winged olives

occurrence

family

common name

Moderate

Moderate

Moderate

Moderate

Moderate

Very high

Riffles

Riffles

Riffles

Riffles

Runs and pools

Runs

abundance habitat

Mayfly availability to trout, habitat, typical emergence, and usual maximum body length

Mid-May through mid-June

Early May through mid-June

Early April through late June; early September through late October

Early April through late August (most from April through June)

Early April through mid-May; early June through late September

Late February through early May; early September through late October

emergence period

a ppen dix b: mayfly attri butes and simple fly patterns

20 mm (0.8 inch)

18 mm (0.7 inch)

12 mm (0.5 inch)

20 mm (0.7 inch)

15 mm (0.6 inch)

12 mm (0.5 inch)

max. body length

Ephemerellidae

Ephemeridae

Isonychiidae

Hendricksons, red quills, and sulphurs, pale evening duns

Green drake, yellow drake, white fly, golden drake, brown drake

Slate drake

Common

Common

Very common

Moderate

Very high

High

Pools

Runs and pools

Riffles, runs and pools

Mayfly availability to trout, habitat, typical emergence, and usual maximum body length (cont.)

Mid-May through mid-July

Mid-May through early June; early June through early mid-July

Early April through early May; late May through early July

14 mm (0.55 inch)

50 mm (2.0 inch)

15 mm (0.6 inch)

Appendix B  |  91

16–20 nymph

14–20 2X nymph Black

Leptophlebiidae

Epeorus sp.

Quill Gordon, pink lady, and gray-winged quill

16–18 nymph

14–16 nymph

Hendrickson/red quill Ephemerella subvaria

E. invaria

10–14 nymph

Cream and light cahills Stenonema and Heptagenia

Big sulphur/pale evening dun

10–14 2X nymph

March brown/gray fox Maccaffertium vicarium

tail

Olive

Black

Brown

Brown

Black

Mallard flank

Olive mallard flank

Pheasant tail

Pheasant tail

Moose mane

Moose mane

Olive or tan Olive mallard flank

Blue and black quills

16–22 nymph

Baetidae

thread

Little blue-winged olives

hook

family

common name

Simple fly patterns designed to imitate common mayfly nymphs wing pads

Mink dubbing Brown turkey tail

Olive dubbing Grouse wing

thorax

Black/olive dubbing

Mottled turkey tail

Grouse flank

Grouse flank

Grouse flank

Grouse flank

Olive mallard flank

legs

Olive dubbing Light turkey quill

Mallard flank

Black turkey tail Olive mallard flank

Olive dubbing Mottled turkey tail

Tan dubbing

Muskrat dubbing with strand Natural of peacock herl along the back, muskrat ribbed with fine copper wire

Olive-brown dubbing ribbed with fine gold wire

Tan dubbing ribbed with fine gold wire

Mink dubbing, ribbed with os- Mink dubbing Brown turkey trich herl and fine copper wire tail

Mink dubbing ribbed with copper wire

Olive dubbing

abdomen

92  |  appendix b

12–14 2X nymph

Isonychiidae

Slate drake

18 nymph

8–12 2X curved nymph

E. dorothea

Green drake, yellow Ephemeridae drake, white fly, golden drake, brown drake

Little sulphur/pale evening dun

Black

Tan

Brown

Simple fly patterns designed to imitate common mayfly nymphs (cont.)

Pheasant tail

Pheasant tail

Grouse flank

Seal-colored dubbing ribbed with red peacock herl and ribbed with copper wire

Creamy ginger dubbing with strand of ostrich herl along the back and ribbed with fine copper wire

Mink dubbing with strand of peacock herl along the back and ribbed with fine gold wire

Grouse flank Dark turkey quill with flashsynthetic strip over the top

Seal-colored dubbing

Pheasant tail

Grouse flank

Light turkey

Light turkey

Ginger dubbing

Natural mink

Appendix B  |  93

family

Chloroperlidae

Peltoperlidae

Perlidae

Perlodidae

Pteronarcyidae

common name

Green stoneflies or sallflies

Roachflies

Common stoneflies

Little yellow stoneflies

Eastern giant stoneflies

Common

Common

Very common

Common

Common

occurrence

Moderate

High

Moderate

Very high

High

abundance

Leaf packs

Riffles and runs

Riffles and runs

Leaf packs

Riffles and runs

habitat

Stonefly availability to trout, habitat, typical emergence, and usual maximum body length

a ppen dix c : sto nefly attri butes and simple fly patterns

April to June

May throughout July

May to August

June to July

May to July

emergence period

50 mm (2.0 inches)

15 mm (0.6 inch)

30 mm (1.2 inches)

15 mm (0.6 inch)

18 mm (0.7 inch)

max. body length

family

Chloroperlidae

Peltoperlidae

Perlidae

Perlodidae

Pteronarcyidae

common name

Green stoneflies or sallflies

Roachflies

Common stoneflies

Little yellow stoneflies

Eastern giant stoneflies

6–10 curved nymph

12–16 curved nymph

6–12 curved nymph

12–14 scud

12–16 2X curved nymph

hook

Black

Brown

Yellow

Brown

Brown

thread

Simple fly patterns designed to imitate common stonefly nymphs

Dark goose biots

Ginger hackle barbs for tail and yellow goose biots for legs

Ginger goose biots

Ginger goose biots

Tan or yellow goose biots

tail, legs, and/or antennae

Dark brown dubbing copper wire

Ginger dubbing brown monocord

Yellow or tan dubbing wrapped with latex and ribbed with brown tubing

Reddish-brown dubbing wrapped with latex and ribbed with copper wire

Tan dubbing wrapped with latex and ribbed with copper wire

abdomen

Dark brown dubbing

Dark turkey tail

Male pheasant hackle

Turkey tail

Yellow or tan dubbing Ginger dubbing

Dark turkey tail

Latex or turkey tail

wing pads

Reddishbrown dubbing

Seal-colored dubbing

thorax

Appendix C  |  95

family

Chironomidae

Simuliidae

Tipulidae

Tabanidae

Athericidae

common name

Midges

Black flies

Crane flies

Horse flies and deer flies

Snipe flies

Common

Common

Common

Common

Very common

occurrence

Moderate

Moderate

High

Very high

Very high

abundance

Runs and pools

Ubiquitous

Ubiquitous

Riffles and runs

Ubiquitous

typical habitat

Dipteran larvae availability to trout, habitat, typical emergence, and usual maximum body length

a ppen dix d : d ip teran attri butes and simple fly patterns

May through July

May through August

March into October

April into June

Throughout the year

emergence

20 mm (0.8 inch)

60 mm (2.4 inches)

100 mm (3.4 inches)

15 mm (0.6 inch)

30 mm (1.2 inches)

max. body length

family

Chironomidae

Simuliidae

Tipulidae

Tabanidae

Athericidae

common name

Midges

Black flies

Crane flies

Horse flies and deer flies

Snipe flies

12–14 nymph

10–16 nymph

8–16 nymph or scud

16–20 scud

18–22 scud or nymph

hook

Brown or black

Tan

Tan

Tan

Various shades of yellow, cream, green, and red

thread

Simple fly patterns designed to imitate common dipteran larvae thorax

Tan or brown dubbing ribbed with same as abdomen

Dubbing, same or darker than abdomen

Blended olive, brown, and green dubbing ribbed with Same as abdomen monocord, monofilament, or fine wire; use marabou or similar feather fibers for “tail”

Rabbit fur tail, cream or amber dubbed abdomen, ribbed with similar color monocord

Rabbit fur tail, cream, brown, or amber dubbing ribbed with similar color monocord

Green floss or similar material, ribbed with monocord Amber dubbing or wire, then coated with head cement

Various materials and colors (same as thread), ribbed Same as abdomen, use darker with material darker than body to define segmentamaterial than body for pupae tion

abdomen

Appendix D  |  97

family

Corydalidae

Asellidae

Gammaridae

Cambaridae

common name

Hellgrammites

Sowbugs

Scuds

Crayfish

Very common

Common (limestone streams)

Common (limestone streams)

Very common

occurrence

Moderate

Very high

Very high

Moderate

abundance

Ubiquitous

Ubiquitous (algae and vegetation)

Ubiquitous (algae and vegetation)

Riffles and runs

typical habitat

Present year-round

Present year-round

Present year-round

April through September but present year-round

emergence

Hellgrammite and noninsect arthropod availability to trout, habitat, typical emergence, and usual maximum body length

150 mm (6.0 inches)

20 mm (0.8 inch)

20 mm (0.8 inch)

90 mm (3.6 inches)

max. body length

appendix e: hellgrammite and noninsect arthropod attributes and simple fly patterns

family

Corydalidae

Asellidae

Gammaridae

Cambaridae

common name

Hellgrammites

Sowbugs

Scuds

Crayfish

Tied upside down on size 2– 10 curved nymph

12–16 scud

12–16 nymph

4–10 curved nymph

hook

Tan or brown

To match abdomen

Gray or black

Brown or black

thread

Simple fly patterns designed to imitate hellgrammites and noninsect arthropods

Nonlead eyes for weight, wrapped or dubbed rabbit for underbody (trimmed), foam shellback

Shades of cream, olive, tan, or orange dubbing with plastic or latex shellback, ribbed with monofilament, gold, or copper wire

Trimmed, wrapped ostrich herl with plastic or latex shellback, ribbed with gold or copper wire

Tan dubbing wrapped with brown latex, then ribbed with ginger hackle and copper wire

abdomen

Rubber legs, rabbit strips for pincers, flashy synthetic for antennae and dubbed or wrapped rabbit underbody

Same as abdomen, hackle tips to match body color

Same as abdomen, grizzly hackle tips for antennae

Brown or black dubbing with turkey tail wing case and goose biots for mandibles

thorax

Appendix E  |  99

Caddisfly anatomy

Head

Eyes

Thorax

Legs

Anal claws

Gills

Abdomen

appendix f: generalized caddisfly and mayfly/stonefly anatomy

Mayfly/stonefly anatomy

Antennae

Head

Eyes

Legs

Thorax

Wingpads

Abdomen

Gills

Cerci (tails)

Appendix F  |  101

references

Fauceglia, Ted. 2005. Mayflies. Mechanicsburg, Pa.: Stackpole Books. Hafele, Rick. 2006. Nymph-Fishing Rivers and Streams: A Biologist’s View of Taking Trout Below the Surface. Mechanicsburg, Pa.: Stackpole Books. Hughes, Dave. 2005. Handbook of Hatches: A Basic Guide to Recognizing Trout Foods and Selecting Flies to Match Them. Mechanicsburg, Pa.: Stackpole Books. Meck, Charles, and Paul Weamer. 2009. Pocketguide to Pennsylvania Hatches. New Cumberland, Pa.: Headwater Books. Merritt, Richard W., Kenneth W. Cummins, and Martin B. Berg. 2008. An Introduction to the Aquatic Insects of North America. Dubuque: Kendall Hunt. Osthoff, Rich. 2008. Active Nymphing: Aggressive Strategies for Casting, Rigging, and Moving Nymphs. Mechanicsburg, Pa.: Stackpole Books. Peckarsky, Barbara L. 1990. Freshwater Macroinvertebrates of Northeastern North America. Sacramento: Comstock. Schwiebert, Ernest G. Nymphs. Volume 2, Stoneflies, Caddisflies, and Other Important Insects. Guilford, Conn.: The Lyons Press. Smith, Douglas Grant. 2001. Pennak’s Freshwater Invertebrates of the United States. 4th ed. New York: John Wiley and Sons. Stewart, Kenneth W., and Bill P. Stark. 2002. Nymphs of North American Stonefly Genera (Plecoptera). 2nd ed. Columbus: The Caddis Press. Voshell, J. Reese Jr. 2002. A Guide to Common Freshwater Invertebrates of North America. Granville, Ohio: McDonald and Woodward. Wiggins, Glenn B. 2004. Caddisflies: The Underwater Architects. Toronto: University of Toronto Press. Wolf, Dave. 1999. Flyfisher’s Guide to Pennsylvania. Belgrade, Mont.: Wilderness Adventures Press.

index

Page numbers in italics refer to illustrations. abdomen, 8 Adams dry fly pattern, x aestivation, state of, 7 alderflies (sialidae), 77–79, 78 Annulipalpia caddisflies, 10–11 apple caddisflies (Brachycentridae), 21–22, 22 aquatic arthropods, 1 aquatic habitats of dipterans, 65 arthropods, 1 artistic flytiers, 2 autumn mottled sedge (Uenoidae), 27–28, 28 black flies, 69–71, 70, 71 black quills (Leptophlebiidae), 34–35, 35 “blood worms,” 68 blue quills (Leptophlebiidae), 34–35, 35 brook trout, 13 brown trout, x brushlegged mayflies, 47, 47–48 butterflies (Lepidoptera), caddisflies compared to, 9 caddisflies (Trichoptera) autumn mottled sedge, 27–28, 28 case-maker, 23–25, 24 characteristics of, 10, 87 dark blue sedge, 26–27, 27 emergence of, 11–12 fly patterns for, 14, 17, 19, 22, 24, 26, 88–89 grannom or apple, 21–22, 22 green or green rock worm, 18–21, 19, 20 larvae of, 8, 9–10, 15 Lepidoptera compared to, 9 little black or fingernet, 16–18, 17 longevity of, 12 netspinner or tan, 10, 13–16, 14, 15 pupae of, 11

104  |  index

caddisflies (Trichoptera) (cont.) smokey winged sedge, 25, 26 suborders and superfamilies of, 10–11 water quality and, 12–13 case-maker caddisflies (Limnephilidae), 23–25, 24 caudal filaments, 8 chocolate dun (Eurylophella) nymph, 4 classic limestone streams, 3 coal mining and streams, 65 common stoneflies (Perlidae), 50, 52, 56–59, 57 countershading, 80–81 crane flies (Tipulidae), 64, 71–73, 72, 73 crayfish (Cambaridae), 83–85, 84 cream light cahills (Stenonema), 40–42, 42 creeping welts, 65–66 crustaceans characteristics of, 1, 98 crayfish, 83–85, 84 fly patterns for, 81, 82, 84, 99 scuds, 81–83, 82 sowbugs, 79–81, 80, 81 dark blue sedge (Odontoceridae), 26–27, 27 “dead drift,” x deer flies (Tabanidae), 73–74, 74, 75 Delaware River, 79 designing nymph patterns, xi diapause stage, 5, 28 Dipterans. See true flies dobsonflies (Corydalidae), 77–79, 78 dragonflies, longevity of, 3 dry fly-fishing, appeal of, ix eastern giant stoneflies (Pteronarcyidae), 60–63, 61 ecosystem integrity, indicators of, 34, 55, 84–85. See also water quality egg masses of caddisflies, 12 of mayflies, 32 release and deposit of, 4–5 sizes and colors of, 5 of stoneflies, 4, 52–53 emergence of adult insects black flies, 70 caddisflies, 11–12

Index  |  105



description of, 5 mayflies, 31, 32, 39 midges, 69 stoneflies, 7 times, ranges of, 2–3

facultative species, 57 fanglike lacina, 51, 52, 54–55 feeding frenzies, 5, 32 fingernet caddisflies (Philopotamidae), 16–18, 17 fish hatcheries, 69 Fishing Creek, 34 flatheaded mayflies (Heptageniidae), 30, 36–37, 37 fly patterns. See also imitating Adams dry, x amber scuds, 82 black flies, 70 for caddisflies, 88–89 common stoneflies, 57 crayfish, 84 dark quills, 35 designing, xi emerging cahills, 41 emerging sulphur nymphs, 45 “giant stick worm,” 24 giant stoneflies, 61 grannom caddis, 22 gravel-cased nymph, 26 gray sowbugs, 81 green caddis, 19 green drakes, 46 green stoneflies, 54 hare’s ear, x, 2 for hellgrammites and noninsect arthropods, 78, 99 horse flies, 74 Isonychia, 48 leadwing coachman, 12 little black caddis, 17 little blue-winged olive nymph, 33 march brown nymphs, 40 matching nymph and, x, 2 for mayfly larvae, 92–93 midges, 68 mini cream crane flies, 72 Montana Stone, 58

106  |  index

fly patterns (cont.) pheasant tail, x, 2 prince nymph, 2 Quill Gordons, 38 roachflies, 56 sally stoneflies, 60 snipe flies, 76 for stoneflies, 95 tan caddis, 14 for true flies, 97 freestone streams, 3 genera, 2 gills imitating, 8, 36 of stoneflies, 51 Gordon, Theodore, 37 grannom caddisflies (Brachycentridae), 6, 11, 21–22, 22 gravel-cased nymphs, 25, 26 gray fox nymphs (Maccaffertium vicarium), 39–40, 40 gray-winged summer quills (Epeorus), 37–39, 38 green drakes (Ephemeridae), 44–47, 46 green or green rock worm caddisflies (Rhyacophilidae), 18–21, 19, 20 green stoneflies (Chloroperlidae), 7, 53–55, 54 habitat types of aquatic dipterans, 65 hare’s ear nymph, x, 2 hellgrammites (Corydalidae and Sialidae), 3, 77–79, 78, 98–99 hemimetabolous insects, 3, 31 hendrickson nymphs (Ephemerellidae), 30, 42–44, 43, 45 holometabolous insects, 3, 9 horse flies (Tabanidae), 73–74, 74, 75 imitating. See also fly patterns adult color, 44 chloroperlids, 53 crane flies, 71 crayfish, 85 emerging caddis, 13 flatheaded mayfly nymphs, 42 gills, 8, 36 green, yellow, and slate drakes, 46 horse and deer flies, 75 mayfly wings, 39

Index  |  107

snipe flies, 76 stoneflies, 58, 62–63 swimming motion, 32–33, 48, 76, 85 tails, 37 instars, 6 Integripalpia caddisflies, 11 larvae of caddisflies, 8, 9–10 time spent as, 5–7 of true flies, 64, 65–66 leadwing coachman pattern, 12 light cahills (Heptagenia), 40–42, 42 little black caddisflies (Philopotamidae), 16–18, 17 little blue-winged olive nymphs (Baetidae), 30, 30, 31, 32–34, 33 Little Juniata River, 21, 79 little yellow stoneflies (Perlodidae), 59, 59–60, 60 longevity of aquatic insects, 3 of caddisflies, 12 of mayflies, 31–32 maggots, 65 mahogany duns (Leptophlebiidae), 34–35, 35 March brown nymphs (Maccaffertium vicarium), 39–40, 40 matching nymphs, x, 2 mayflies (Ephemeroptera) characteristics of, 29–31, 30, 90–91 cream and light cahills, 40–42, 42 flathead, 30, 36–37, 37 fly patterns for, 33, 35, 38, 40, 41, 45, 46, 48, 92–93 green and yellow drakes, 44–47, 46 hendricksons, red quills, and sulphurs, 30, 42–44, 43, 45 larvae of, 8 little blue-winged olive, 30, 30, 31, 32–34, 33 longevity of, 31–32 mahogany duns, blue and black quills, 34–35, 35 March brown and gray fox, 39–40, 40 Quill Gordon, pink lady, and gray-winged summer quills, 37–39, 38 slate drakes great leadwings, 47, 47–48 species of, 29 stoneflies compared to, 40–50 metamorphosis, 7 midges (Chironomidae), 6, 7, 67–69, 68, 69

108  |  index

molting, 6 Montana Stone pattern, 58 mouthparts of black flies, 69, 71 of horse and deer flies, 73 of stoneflies, 51, 52, 54–55 movement of nymphs, 32–33 natural drift, 34 negative phototaxis, 81–82 netspinner caddis (Hydropsychidae), 10, 13–16, 14, 15 noninsect arthropods, 1 nymph, definition of, 3, 8 nymph anglers five Ws and an H for, xi success of, x orders, 2 ostrich herl, 36 overcast skies, 62–63 “peeking caddis,” 21 Penns Creek, 18, 21, 44, 79 periphyton, 25 pheasant tail nymph, x, 2 pink lady nymphs (Epeorus), 37–39, 38 positive thigmotaxis, 37 predaceous stoneflies, 50, 51, 52, 54–55, 57–58 prince nymph, 2 prolegs, 65, 75–76 prong-gilled mayflies (Leptophlebiidae), 34–35, 35 pupae of black flies, 69 overview of, 7–8 of true flies, 66–67 quiescence, state of, 7 Quill Gordon nymphs (Epeorus), 37–39, 38 rain and overcast skies, 62–63 “reading the water,” x red quills (Ephemerellidae), 42–44, 43, 45 riffle-dwelling mayflies, 30 roachflies (Peltoperlidae), 55–56, 56 rusty crayfish, 85

Index  |  109

sallflies (Chloroperlidae), 53–55, 54 sally (little yellow) stoneflies (Perlodidae), 59, 59–60, 60 salmonflies (Pteronarcyidae), 60–63, 61 scuds (Gammaridae), 81–83, 82 shucks, 11–12, 15, 39, 67 sideswimmers, 81–83, 82 slate drakes great leadwings (Isonychiidae), 47, 47–48 small minnow mayflies. See little blue-winged olive nymphs smokey winged sedge (Apataniidae), 25, 26 snipe flies (Athericidae), 75, 75–76, 76 snowflies (Capniidae), 7 sowbugs (Asellidae), 79–81, 80, 81 Spicipalpia caddisflies, 11 spiny crawler mayflies, 42–44, 43 spiracles, 72 Spring Creek, 18, 34, 69 “stick worms,” 23 stoneflies (Plecoptera) characteristics of, 49–53, 50, 52, 94 common, 50, 56–59, 57 eastern giant, 60–63, 61 egg masses, 4, 5 emergence of, 7 fly patterns for, 54, 56, 57, 60, 61, 95 larvae of, 8 little yellow, 59, 59–60, 60 mayflies compared to, 29 mouthparts of, 51, 52, 54–55 roachflies, 55–56, 56 sallflies or green stoneflies, 53–55, 54 streams. See trout streams stripetails (little yellow stoneflies, Perlodidae), 59, 59–60, 60 sulphur nymphs (Ephemerellidae), 30, 42–44, 43, 45 swimming mayflies, 30–31 swimming motion, imitating, 32–33, 48, 76, 85 tan caddis (Hydropsychidae), 13–16, 14 thorax, 8 trout, x, 13, 63 trout streams. See also water quality classifications of, 3 forested, 55 temperatures of, 7 true flies (Diptera) black flies, 69–71, 70, 71

110  |  index

true flies (Diptera) (cont.) characteristics of, 64–67, 96 crane flies, 64, 71–73, 72, 73 fly patterns for, 68, 70, 72, 74, 76, 97 horse and deer flies, 73–74, 74, 75 midges, 67–69, 68 snipe flies, 75, 75–76, 76 wastewater treatment plants, 69, 70 water quality black flies and, 69, 70–71 “blood worms” and, 68 caddisflies and, 12–13 coal mining and, 65 mayflies and, 29 midges and, 69 stoneflies and, 49, 53–54, 58–59 wing pads on mayflies, 31, 31 winter stoneflies (Capniidae), 7 yellow drakes (Ephemeridae), 44–47, 46

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