Larvae of the North American Caddisfly Genera (Trichoptera) (Heritage) [2 ed.] 0802027237, 9780802027238

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Larvae of the North American Caddisfly Genera (Trichoptera) Second edition Caddisflies are one of the most diverse groups of organisms living in freshwater habitats, and their larvae are involved in energy transfer at several levels within these communities. Caddisfly larvae are also remarkable because of the exquisite food-catching nets and portable cases they construct with silk and selected pieces of plant and rock materials. This book is the most comprehensive existing reference on the aquatic larval stages of the 149 Nearctic genera of Trichoptera, comprising more than 1400 species in North America. The book is invaluable for freshwater biologists and ecologists in identifying caddisflies in the communities they study, for students of aquatic biology as a guide to the diverse fauna of freshwater habitats, and for systematic entomologists as an atlas of the larval morphology of Trichoptera. In the General Section, the biology of caddisfly larvae is considered from an evolutionary point of view. Morphological terms are discussed and illustrated and a classification of the Nearctic genera is given. Techniques are outlined for collecting and preserving larval specimens and for associating larval with adult stages. The Systematic Section begins with a key to larvae of the 26 families of North American Trichoptera. Each chapter in this section is devoted to a particular family, providing a summary of biological features and a key to genera, followed by a two-page outline for each genus with illustrations facing text. This outline provides information on general distribution, number of species, distinctive morphological features, and biological data including construction behaviour. An important feature of the book is the habitus illustrations of larvae and cases of a selected species in each genus, along with illustrations of details of significant morphological structures. Each generic type is thus presented as a recognizable whole organism adapted in elegant ways to particular niches of freshwater communities. This revised edition includes advances in knowledge on the classification and biology of Trichoptera up to 1993 - an interval of 17 years since the first edition. An additional eight families and thirteen genera are included for the first time. Through reorganization of the families into three suborders, a biological context has been established for the systematic section. Glenn B. Wiggins is Curator Emeritus in the Department of Entomology, Royal Ontario Museum, and Professor Emeritus in the Department of Zoology, University of Toronto. The first edition was selected by Choice, a publication of the Association of College and Research Libraries, as one of the outstanding academic books of 1978.

GLENN B. WIGGINS

Larvae of the North American Caddisfly Genera (Trichoptera) 2nd edition

UNIVERSITY OF TORONTO PRESS Toronto Buffalo London

© University of Toronto Press Incorporated 1996 Toronto Buffalo London Printed in Canada

ISBN 0-8020-2723-7 (cloth)

Printed on acid-free paper

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Canadian Cataloguing in Publication Data Wiggins, Glenn B. Larvae of the North American caddisfly genera (Trichoptera) 2nd ed. Includes index. ISBN 0-8020-2723-7

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1. Caddisflies - Canada. 2. Caddisflies United States. 3. Insects - Larvae. 4. Caddisflies - Identification. 5. Caddisflies Canada - Identification. 6. Caddisflies United States - Identification. I. Title QL517.1.AIW531996

595.7'45'0971

C95-932174-8

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University of Toronto Press acknowledges the financial assistance to its publishing program of the Canada Council and the Ontario Arts Council.

This book is dedicated to Professor Herbert H. Ross

I consider it as of the utmost importance fully to recognise that the amount of life in any country, & still more that the number of modified descendants from a common parent, will in chief part depend on the amount of diversification which they have undergone, so as best to fill as many & as widely different places as possible in the great scheme of nature. Charles Darwin Charles Darwin's Natural Selection (p. 234) ed. R.C. Stauffer 1975 ,

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Contents

Preface to the First Edition ix Preface to the Second Edition xii

Associating larval stages 37 Preserving, storing, and shipping specimens 38 Studying specimens 40

GENERAL SECTION SYSTEMATIC SECTION

Introduction 3 Objectives 4 Geographic limits 5 Organization and methods 5 Use of keys 7

Key to larvae of North American families of Trichoptera 43

Classification 8

1 2 3 4

Biological considerations 14 Ancestral habitat 14 Habitat diversity 14 Respiration 15 Feeding 19 Construction behaviour 21 Life cycles 22 ,

Morphology 26 Head 26 Thorax 28 Abdomen 30 Techniques 35 Collecting 35

5 6 7 8 9 10 11

Suborder Spicipalpia 49 Family Glossosomatidae 50 Family Hydrobiosidae 67 Family Hydroptilidae 71 Family Rhyacophilidae 110 Suborder Annulipalpia 117 Family Dipseudopsidae 118 Family Ecnomidae 123 Family Hydropsychidae 126 Family Philopotamidae 150 Family Polycentropodidae 159 Family Psychomyiidae 174 Family Xiphocentronidae 185

Suborder Integripalpia 189 12 Family Apataniidae 190 13 Family Beraeidae 203 ..

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Contents 14 15 16 17 18 19 20 21 22

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Family Brachycentridae 206 Family Calamoceratidae 218 Family Goeridae 226 Family Helicopsychidae 237 Family Lepidostomatidae 241 Family Leptoceridae 249 Family Limnephilidae 268 Family Molannidae 352 Family Odontoceridae 359

23 24 25 26

Family Phryganeidae 374 Family Rossianidae 399 Family Sericostomatidae 404 Family Uenoidae 413 Literature cited 427 Taxonomic index 453

Preface to the First Edition

This is a reference work to the identity, structure, and biology of larvae of the North American caddisfly genera. More precisely perhaps, it is a stage in the evolution of such a reference, for a definitive work even at the generic level is still well beyond the information now available. The book is the result of a project I began some years ago to increase knowledge about larval Trichoptera in North America. Systematic collections on which it is based were brought together in the course of more than 150,000 miles of travel in field expeditions through many parts of Canada and the United States, especially in the western mountains where the fauna is highly diverse yet little explored. Associations between larval and adult stages were established for some 350 species, approximately 30% of the 1200 or so species of Trichoptera now known in the two countries; over 200 of these were established for the first time. Although the information made available is still far short of enabling one to produce keys for the identification of North American caddisfly larvae to the species level, it represents a substantial advance at the generic level. Since the genus in the Trichoptera, as in most groups, represents an ecological as well as a morphological type, it provides a useful and an incisive base for generalization. To date, 142 Nearctic genera are recognized and larvae have been identified for all but 6 (4%); diagnostic characters for larvae of 14 genera are given here for the first time, and from this general project characters for an additional 16 genera were originally published elsewhere. Having gained a better understanding of the range of larval characters covered by most genera, I have been able to establish more precise diagnoses for them and consequently have introduced many new characters into the generic keys. Ultimately, of course, keys for identification of larval Trichoptera to the species level will provide the most effective aid to workers in freshwater biology, but, in general, this level of precision is not possible in North America because sufficient basic data have not yet been assembled. I am conscious of my good fortune in having the support of several institutions and agencies in this project. The Royal Ontario Museum has provided the working facilities for my studies, and the documented collections on which they are based are part of the research materials of the Department of Entomology. In the early years of my field work, .

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Preface to the First Edition 1962-68, when intensive surveys were made in the western United States, financial support was received from the National Science Foundation. Operating grants from the National Research Council of Canada have supported the project in recent years. Funds from the Fisheries Research Board of Canada and from the Canadian National Sportsmen's Show have also been received. Substantial grants toward the cost of publishing this book were received from the National Research Council of Canada and the Publications Fund of the University of Toronto Press. For all of this support I am profoundly grateful. Figures for the book were prepared by Mr Anker Odum, until recently the scientific illustrator in our department. They are sufficient evidence of Mr Odum's considerable ability in this field and of his own fascination with insects; I shall add only that I have worked closely with him in an attempt to ensure that every drawing conveyed as much accurate morphological information as possible. Individual acknowledgment to all of the persons who have contributed in some way to this project is not possible here, but I am most grateful for the cooperation, generosity, and encouragement that I have everywhere received. To Mr Toshio Yamamoto of our department lowe special gratitude for his knowledgeable and enthusiastic assistance in field work and innumerable other aspects of the project. Several others who were members of our field expeditions have contributed substantially to the growth of the collections on which the work is based: D. Barr, H.E. Frania, L.H. Kohalmi, B.P. Smith, LM. Smith, and the late R.S. Scott. Professor Rosemary Mackay of the University of Toronto has been helpful in resolving ecological matters and problems of many kinds. It is this sense of community in acquisition and analysis of the collections which underlies use of the pronoun we throughout. My professional colleagues have responded generously to requests for specimens, information, and comment. It is a pleasure to acknowledge this cooperation from N.H. Anderson, D.G. Denning, O.S. Flint, J.e. Morse, Y.H. Resh, H.H. Ross, F. Schmid, S.D. Smith, J.D. Unzicker, and J.B. Wallace. Students in Aquatic Entomology at the University of Toronto and at the Lake Itasca Biology Sessions of the University of Minnesota (1970, 1972, and 1974) helped me to appreciate that keys for identification of insects are too often inconclusive and inadequately illustrated. In affording me opportunities to test earlier versions of the present keys, they also helped to confirm my suspicion that when effort is invested in producing extensively illustrated keys, learning can be'at least easier and is more often exciting. Services made available through the Royal Ontario Museum are invaluable in a work of this kind, and this book represents supporting contributions of many persons: those . involved in the entire museum process lead(ng to deposition of adequately documented • specimens in the research collection, secretaries and photographers in hours of careful work during preparation of the manuscript;· arid librarians for their efforts to maintain the reference base essential for research in systematics. I wish also to acknowledge the assistance of lC.E. Rioue for translation of important reference works, Sharon Hick for compiling the literature citations, Zile Zichmanisfqr art work, and Felix Barlocher for analysis of larval food. In acknowledging these contributions, I extend my appreciation to those directors and trustees of the Royal Ontario Museum whose support my work has had over the years of my curatorial appointment. I hope that they will see in this book another example of the ROM's 'record of nature through countless ages.' x

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Preface to the First Edition In matters relating to publication, Lorraine Ourom and Ian Montagnes of the University of Toronto Press have given me advice and encouragement. Facilities for some of the field work were made available by several institutions: American Museum of Natural History, Southwestern Research Station, Portal, Arizona; University of Minnesota, Lake Itasca Forestry and Biological Station; Oregon State University, Corvallis; Queen's University Biological Station, Chaffeys Locks, Ontario; University of California Sagehen Creek Research Project, Truckee; University of Montana Biological Station, Yellow Bay, Flathead Lake; Harkness Research Laboratory, Ontario Ministry of Natural Resources, Algonquin Provincial Park. My wife and children shared many of the longer field expeditions, and more recently contended with my long preoccupation during preparation of the manuscript. I have appreciated their companionship and assistance as well as their forbearance. Finally, I acknowledge a debt to those who have gone before me. Identification of the North American caddisfly larvae was at best uncertain before appearance of H.H. Ross's Caddis Flies or Trichoptera of Illinois in 1944, and was again improved at the generic level by his contribution to the revised edition of Ward and Whipple (ed. Edmundson 1959). Taxonomic refinement by Ross, D.G. Denning, F. Schmid, O.S. Flint, and others has continued to develop the classification of the Nearctic Trichoptera into a most useful scientific asset. In offering the present work as a further step in the evolution of a fundamental faunal reference for larval Trichoptera on this continent, I am mindful that it builds upon the work of others. It is my hope that this book will have some part in the development of freshwater biology, bringing nearer the time when the diversity of freshwater communities can be adequately understood, and ultimately preserved. It has been my privilege to explore freshwater habitats over much of North America; in studying creatures seldom seen by others, I have delighted in sensing the timeless grandeur of natural processes that shaped them as they are. Perhaps this book will also bring to others more of those uniquely human insights that come from seeing and comprehending the life with which we share this planet. G.B.W. March 1976

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Preface to the Second Edition

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This second edition is an extensive revision of the 1977 book, advancing the information base up to the end of 1993. During the interval of 17 years since the manuscript for the 1977 edition was completed, a substantial amount of new knowledge on North American larval Trichoptera has been published, and advances have been made in classification to reflect new understanding of the phyletic relationships of families and genera. Eight families and 13 genera are added in this revised edition, with a net increase of seven in the number of North American genera recognized to bring the total to 149; larvae remain unidentifiable for four of those genera. The number of species recognized in the North American fauna of Trichoptera rose to 1340 by the end of 1987 (Wiggins 1990); and if the rate of increase has averaged about the same at 10 species per year, the total is estimated to have reached approximately 1400 species by the end of 1993. Organization of the families in the systematic section in this revised edition is based on three suborders (Wiggins and Wichard 1989; Frania and Wiggins 1995), establishing an underlying biological context. Larvae of proven identity continue to be the building blocks for a work of this kind. A number of these associations have come from our field work since 1977; some have been made available through the work of others, and are acknowledged at appropriate points in the book. In organizing new materials and information for the book, I have been aided in many ways by members of the ROM Department of Entomology. Patricia Schefter has processed large numbers of new accessions for the research collection; and in her reviews of series of specimens to test putative diagnostic characters, she has discovered several new character systems. For genera not previously included in the book, new illustrations have been prepared by P.L. Stephens-Bourgeault. Most of the illustrations are those prepared for the first edition by Anker Odum, with some others by Clare Storwick and Karl Pogany. The book has been enriched by the contributions of these talented artists, and I am grateful to the Royal Ontario Museum for making possible this assistance. Catherine Rutland has done much to bring about the transformation of the manuscript for this second edition from the first; Roslyn Darling assisted with word-processing. Throughout the period between the two editions, my work has been supported by an ..

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Preface to the Second Edition operating grant (A5707) from the Natural Sciences and Engineering Research Council of Canada. A good deal of new information has been contributed to this revision through research by graduate students supported from the grant: B.D. Beam, H.E. Frania, E.R. Fuller, WK. Gall, J.D. Kerr, P.W Schefter, R.N. Vineyard, and N.E. Williams. As in the first edition, a number of colleagues have provided specimens and information. It is a pleasure to acknowledge this assistance from N.H. Anderson, L. Boto~aneanu, D.E. Bowles, D.G. Cobb, N.E. Erman, WL. Fairchild, O.S. Flint, T.M. Green, S.c. Harris, J.G. Irons, D.1. Larson, M.L. Mathis, S.R. Moulton, M.W. Oswood, C.R. Parker, J.S. Richardson, G. Roemhild, D.E. Ruiter, M.W Sanderson, G.G.E. Scudder, D.H. Smith, K.W. Stewal1, J.R. Voshell, W. Wichard, and R.W Wisseman. I thank editor John St James and staff members of University of Toronto Press for their careful work in producing the book. Finally, for much of the field work related to this second edition, my wife Carol has been both assistant and companion; for that, and for her patience and support during the preparation of this and other manuscripts, I am grateful. G.B.W March 1994

X111

GENERAL SECTION

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Introduction

In no small way, aquatic insects help to sustain streams, rivers, marshes, and lakes as functional, productive ecosystems; and caddisflies are major components of all of these communities. Caddis flies, or Trichoptera, * are a relatively small order of insects widely distributed on almost every habitable land mass. Between 9000 and 10,000 species are now known in the world, but the rate at which species new to science continue to be discovered indicates that the actual world fauna is very much larger (Malicky 1973, 1993; Schmid 1984). These insects have made little impact on popular attention, probably because most adult caddisflies are small greyish brown, moth-like insects active mainly at night; and also because larval caddisflies live in water, where they are well enough concealed to escape notice by casual observers. Caddisflies, however, are common; and their larvae are usually abundant in freshwater habitats, which means that these insects are important components of aquatic systems (Wiggins and Mackay 1978). Because caddisflies have evolved by exploiting resources of the full range of freshwater habitats from cold springs, through streams, rivers, ponds, and marshes, to the shorelines and depths of lakes, and to temporary pools, they contribute to the transfer of energy and nutrients through the trophic levels of all freshwater systems. This broad diversification underlies both the abundance and the importance of caddisflies in freshwater biology. Apart from their ecological roles in aquatic communities, caddisflies are themselves remarkable animals. Most biologists are aware that the larvae of these insects build shelters, but few have seen the exquisite seine-like caddis nets fastened in thousands to the rocks of rivers and streams everywhere; and not many appreciate that the protective tubu-

* The name Trichoptera is derived from the Greek trichos ('hair') and pte ron ('wing'), in reference to the hair covering on the wings of the adults. The origin of caddisfly is obscure, but according to Hickin (1967) it dates in reference to these insects at least to Izaak Walton's Compleat Angler (1653; 'cod-worm or caddis'). In reference to cotton or silk materials, various versions of the word date to 1400; and cadysses appeared in Shakespeare's The Winter sTale (1611) in this sense. Although connection between the two usages has not been firmly established, Hickin states that itinerant vendors of pieces of cloth fastened bits to their clothing as an advertisement and were called cadice men, suggesting a parallel with the case-making larvae.

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Introduction lar cases constructed by caddis larvae lead to the use of silk to increase respirational efficiency, enabling caddisfIies to exploit the resources of lentic habitats. The variety of structures built by caddis larvae ought to have established them among the most fascinating of all insects; but the diversity in caddisfly larval behaviour is largely unappreciated. The production of silk by caddis larvae, and the varied behaviours through which silk is utilized in constructing different types of cases and retreats, are significant factors broadening the biological diversity of Trichoptera (Mackay and Wiggins 1979). Silk has enhanced the partitioning of habitats and trophic resources by Trichoptera. Consequently, caddisflies are particularly finely tuned as indicators of perturbations in freshwater ecosystems; and identification of larvae at the species level is a valuable aid in monitoring the health of those systems (Resh and Unzicker 1975). Aquatic insect larvae are widely used in several aspects of water-quality assessment, and Trichoptera are essential components of those investigations (Resh 1993). Data on pollution tolerance of larval Trichoptera have been compiled by Harris and Lawrence (1978). Since fresh waters are one of the most basic of all natural resources, the communities of organisms that live within them and underlie their productivity and ecological harmony have to be subjects of high priority for scientific study. Even so, freshwater biologists have always had problems in elucidating the precise ecological roles of insect species in a community, largely because their larval stages are difficult to identify. Insufficient taxonomic work on the larvae of caddisflies, and indeed of all aquatic insects, remains a severe barrier to the progress of freshwater biology (Wiggins 1966; Hynes 1970).

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OBJECTIVES

There is, then, a place for a reference work on North American caddisfly larvae. This book could have taken several forms, but I have organized the information with the needs of three groups of users in mind. For freshwater biologists and ecologists, I have attempted to provide the means for precise identification of families and genera of caddisfly larvae in aquatic communities throughout North America, augmented by some biological information and references to the scientific literature. Identification of larvae to the species level is the ultimate goal, but except for a few of the smaller families, that goal lies far beyond our present knowledge. For university students concerned with various aspects of aquatic biology, the book is intended to introduce Trichoptera as important components of freshwater communities. Taxonomic diversity in these communities may be itself an object in teaching, or a means to demonstrate ecological principles. In either case, discovering how many different types of organisms there are in a freshwater community can be a revealing experience for students; and identification of the organisms is the key to understanding their role in the community. I hope that the book will also encourage the use of caddisfly larvae in experimental studies of construction behaviour. Thus, for students I have attempted to make generic groups more than disconnected sets of morphological characters, and to make them come alive as whole organisms adapted in elegant ways to particular niches of the freshwater community. Finally, for systematists, I have tried to produce a reference that would serve as an atlas of gross morphology of the trichopteran larval types in North America. It is well estab4

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Introduction lished that data from larval morphology can be critical in assessing systematic relationships of Trichoptera (and other insects), and for advancing hypotheses concerning their phylogeny (Wiggins 1981), but much of this morphological information is widely dispersed or is not available in the literature. Within the constraints of design and space estab. lished by the first two objectives, compromise is often made in this third one, with the result that illustrations of smaller structures in many groups have not been included. GEOGRAPHIC LIMITS

The genera covered are all those currently recognized within the Nearctic region, excluding the islands of the Caribbean. The species totals given for each genus are those known to occur in Canada and the United States up to the end of 1993. In summaries of global distribution for families and genera, it will be understood that no Trichoptera are extant in Antarctica. ORGANIZATION AND METHODS

This book is primarily a reference work. Families are grouped in three suborders, arranged in alphabetical sequence within each one, and numbered consecutively from 1 to 26. Within each family the genera are arranged alphabetically and numbered consecutively such that the reference number 20.12 specifies Limnephilidae (family no. 20); Dicosmoecus (limnephilid genus no. 12); individual illustrations on each plate are lettered consecutively A, B, etc. A classification of the North American families, subfamilies, and genera is provided on pp. 8-13. A rather large part of the book is devoted to illustrations because this is the most effective way of communicating morphological information. Fine distinctions in form and proportions of body parts are useful in identification, and can be best conveyed by illustration. The stylized arrangement of the legs in the habit figures is made to permit a clear view of the relative lengths of segments and of setal arrangement. Abdominal gills are drawn to reveal their segmental position. In the figures of head and thorax, all parts are shown usually in full dorsal view, although they would not be seen simultaneously in that relationship in life. Illustrations of cases and retreats are provided in some number because these structures provide excellent field characters for generic recognition, and also because they rank among the extraordinary constructions of any animal. The General Section is concerned with various aspects of existing knowledge of the Trichoptera. Biological Considerations is an attempt to place aspects of habitat, respiration, feeding, construction behaviour, and life cycles in an ecological and evolutionary context. The structure of caddisfly larvae is considered in the chapter on Morphology. Under Techniques are discussed methods of collecting, rearing, preserving, and studying larval specimens. Illustrations in the General Section are designated by Roman numerals. In the Systematic Section, the key to families includes all those nOw recognized in the Nearctic region. General features of each family are outlined under the family heading; the genera in each family are arranged alphabetically, but an indication of the broad relationships among genera can be obtained from the groupings in subfamilies or tribes. For each genus a summary of essential features is provided. Under Distribution and Species is given 5

Introduction the general world distribution of the genus; distribution in North America is based on literature records compiled for an Annotated Catalogue of the Trichoptera of North America North of Mexico (Wiggins and Flint, in prep.), which includes some records from the ROM collection not published previously. The number of species known in Canada and the United States is provided, but in many genera these totals will be increased as more faunal exploration is done. Literature references are given for larval diagnoses and descriptions at the species level. By indicating for each genus the number of species known as larvae, both in the literature and in our collections, I have shown the base on which the present generic diagnoses rest. In many genera this base represents only a small part of the total number of species known, and users of this book should be aware that larvae yet to be discovered may render some of the diagnoses inadequate for particular genera. Information summarized for each genus under Morphology pertains largely to features diagnostic for the genus, or to general features that would help to confirm an identification made by using the keys. The length given for the larva is usually that of the largest specimen examined, or occasionally of one recorded in the literature; the measurement is a straight line on the long axis of the body from the anterior margin of the head, usually as positioned in the habit figures of larvae, to the posterior edge of the anal proleg but does not include protruding setae. The larva illustrated is not necessarily the largest one examined, but in almost all genera, the larva illustrated is a final instar. Magnifications given in the figure captions for habit drawings of larvae in most families are based on a straightline measurement of the entire larva, as indicated above; but in the families of the Annulipal pia, where preserved larvae are usually strongly curved and difficult to measure, the magnification is based on length of the head capsule from the posterior margin to thc antcrior border of the frontoclypeal apotome, excluding labrum and mandibles. Under Case, or Retreat for those groups in which the larval structure is fixed in one place, are outlined essential features of these larval constructions. Illustrations of portable cases include an end-on view of the posterior end of the case, an important functional and diagnostic feature of case-making behaviour. The case length given is the maximum in material I have studied or for specimens recorded in the literature. Generic data summarized under Biology are drawn from our collections and field observations, supplemented wherever possible by pertinent literature references; these and other references should always be consulted for additional information because I have made only summary statements. Food studies by others have been cited whenever available, but for many genera there is no information on food in the literature. For some of these, temporary slide mounts of the entire gut content were prepared, and examined under magnifications up to 400x. Visual estimates were made of proportions of components on the slide; usually the guts of three larvae were examined, the number of specimens expressed in parentheses in the text. It is my intention only to provide the basis for some statement of items ingested where none was available previously; no illusion is held concerning the quantitative and seasonal basis of the samples. Comments under Remarks often include references to important taxonomic reviews of adult stages of North American species in the genus under consideration because these sources might not be known to many users of this book, but could be useful if adults were associated with larvae. Where no reference is given to works dealing with taxonomy of the adults, either under this heading or elsewhere, it can be assumed that the most useful 6

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Introduction general review for that genus is still to be found in the classic Caddis Flies, or Trichoptera, of Illinois by H.H. Ross (1944). Taxonomic and nomenclatorial designations are not cited in this work; most will be found in the Trichopterorum Catalogus, of which 15 volumes have been published (Fischer 1960-73). The taxonomic index to the present work lists all genera and higher taxa mentioned, and includes synonyms established since 1944. USE OF KEYS

The keys and diagnostic characters in this book are based on final instars; some diagnostic characters may be effective for later subterminal instars but others are not, especially those relating to setae and gills, which can change at each ins tar. As a general principle, diagnosis of subterminal instars is not possible for larval Trichoptera. Recognition of final instars improves with experience. Subterminal instars tend to have cases or retreats of flimsy construction; pieces of plant or mineral material are easily separated, probably because of economy in the amount of silk protein invested in structures , that have relatively short-term use. Early instar larvae have a juvenile appearance; gills and setae are often short and sparse, and sclerotized areas are more pliable than in larvae that are fully developed. If in a series of larvae collected at one site, the specimens appear to be generally similar to one another but differ in size, the largest larvae should be identified first; and if the smaller specimens give difficulty with the keys, the possibility can be considered that they are early stages of the larger larvae and therefore inappropriate for any keys. In general, users are encouraged to cultivate an approach to identification with keys that avoids investing time in young larvae for which no diagnoses exist. If their identity is important, it is more effective to return to the site at a later date and obtain fully developed larvae. Larval stages are known for a fraction of the species in many genera, and larvae not yet known, when identified, will undoubtedly reveal some of the generic diagnoses to be imprecise. Larvae in four genera have yet to be discovered; these deficiencies are specified in the general sections treating the families concerned and may, when known, affect the accuracy of diagnoses for related genera. Larval associations for a few genera are proposed tentatively on the basis of circumstantial evidence, but the qualifications are stated in the generic section. In making generic identifications with this book, users who do not recognize the families of Trichoptera at sight should first identify specimens with the key to families; the general outline for a family should be used to corroborate placement made through the key, and the appropriate key to genera can then be entered with assurance. At the level of both family and genus, reliance on the illustrations alone will lead to misidentification because the plates do not necessarily include every condition of a character represented within a group. The keys are designed to eliminate sequentially taxa that share certain distinctive characters; the text summary for each genus deals with supporting characters and should be consulted. Corroboration of determinations from distributional information should always be sought. A key to pupae of North American families of Trichoptera is available elsewhere (Wiggins 1984a). Generic keys are available to pupae in a few families (Ross 1944). 7

Classification

Three suborders and six superfamilies are recognized here in the Trichoptera, in accordance with phylogenetic evidence and proposals outlined at length by Frania and Wiggins (1995). A higher classification of three superfamilies - Rhyacophiloidea, Hydropsychoidea, and Limnephiloidea - was employed by Ross (1956, 1967) and is widely used elsewhere, including the first edition of this book. The three suborders employed here Spicipalpia, Annulipalpia, and Integripalpia - are equivalent to the three superfamilies of Ross (1956), but are based on independent phylogenetic analysis of much new evidence (Frania and Wiggins 1995). The superfamilies used here are in accordance with the groups of Frania and Wiggins (1995) and Gall and Wiggins (in press). Grouping by tribe is outlined under the family heading as appropriate. The classification for North American genera employed in this book is outlined below. Genera for which larval stages are unknown are marked with an asterisk. *

SPICIPALPIA (Closed-cocoon makers) Rbyacophilidae Himalopsyche Banks Rhyacophila Pictet

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Principal reference p.49 p. 110 4.1 4.2

Hydrohiosidae Atopsyche Banks

p.67 2.1

Hydroptilidae Subfamily Ptilocolepinae Palaeagapetus Ulmer

p.71 p. 73 3.13

Subfamily Hydroptilinae Agraylea Curtis Alisotrichia Flint Dibusa Ross

p. 73 3.1 3.2 3.3

Classification Hydroptila Dalman Ithytrichia Eaton Leucotrichia Mosely Mayatrichia Mosely Metrichia Ross Neotrichia Morton Ochrotrichia Mosely Orthotrichia Eaton Oxyethira Eaton Paucicalcaria Mathis & Bowles Stactobiella Martynov Zumatrichia Mosely

Glossosomatidae Subfamily Glossosomatinae Anagapetus Ross Glossosoma Curtis

304 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.14 3.15 3.16

p.50 p.51 1.2 1.4

Subfamily Agapetinae Agapetus Curtis

p.51 1.1

Subfamily Protoptilinae Culoptila Mosely Matrioptila Ross Protoptila Banks

p. 52

ANNULIPALPIA (Fixed-retreat makers) Philopotamoidea Philopotamidae Subfamily Philopotaminae Dolophilodes Ulmer Wormaldia McLachlan

p. 117

Subfamily Chimarrinae Chimarra Stephens

p. 151 8.1

Hydropsychoidea Psychomyiidae Subfamily Psychomyiinae Lype McLachlan Psychomyia Latreille Tinodes Curtis

1.3 1.5 1.6

p. 150 p. 151 8.2 8.3

p.174 p.174 10.1 10.3 lOA

Subfamily Paduniellinae Paduniella Ulmer

p.174 10.2

Xiphocentronidae If Xiphocentron Brauer

p. 185 11.1 9

Classification Cnodocentron Schmid*

p. 185

Dipseudopsidae Phylocentropus Banks

p. 118 5.1

Ecnomidae Austrotinodes Schmid

p. 123 6.1

Polycentropodidae Subfamily Polycentropodinae Cemotina Ross Cy me II us Banks Neureclipsis McLachlan Nyctiophylax Brauer Polycentropus Curtis Polyplectropus Ulmer

p. 159 p. 160 9.1 9.2 9.3 9.4 9.5 9.6

Hydropsychidae Subfamily Arctopsychinae Arctopsyche McLachlan Parapsyche Betten

p. 126 p. 127 7.1 7.8

Subfamily Diplectroninae Diplectr01U1 Westwood Homoplectra Ross Oropsyche Ross*

p. 127 7.3 7.4 p. 128

Subfamily Hydropsychinae Cheumatopsyche Wallengren Hydropsyche Pictet Potamyia Banks Smicridea McLachlan

p. 128 7.2 7.5 7.9 7.10

Subfamily Macronematinae Leptonema Guerin-Meneville Macrostemum Kolenati

p. 128 7.6 7.7

INTEGRIPALPIA (Portable-case makers) Phryganeoidea Phryganeidae Subfamily Yphriinae Yphria Milne

p.374 p. 375 23.10

Subfamily Phryganeinae Agrypnia Curtis Banksiola Martynov Beothukus Wiggins Fabria Milne Hagenella Martynov

p.375 23.1 23.2 23.3 23.4 23.5

10

p. 189

Classification

Oligostomis Kolenati Oligotricha Rambur Phryganea Linnaeus Ptilostomis Kolenati

23.6 23.7 23.8 23.9

Limnephiloidea Brachycentridae Adicrophleps Flint Amiocentrus Ross Brachycentrus CUltis Eobracllycentrus Wiggins Micrasema McLachlan

p.206 14.1 14.2 14.3 14.4 14.5

Lepidostomatidae Subfamily Lepidostomatinae Lepidostoma Rambur Subfamily TheJiopsychinae Theliopsyche Banks

p.24l p.242 18.1 p.242 18.2

Rossianidae Goereilla Denning Rossiana Denning

p.399 24.1 24.2

Limnephilidae Subfamily Dicosmoecinae Allocosmoecus Banks Amphicosmoecus Schmid Cryptochia Ross Dicosmoecus McLachlan Ecclisocosmoecus Schmid Ecclisomyia Banks Eocosmoecus Wiggins & Richardson lronoquia Banks Onocosmoecus Banks

p.268 p.269 20.1 20.2 20.10 20.12 20.13 20.14 20.15 20.24 20.28

Subfamily Pseudostenophylacinae Pseudostenophylax Martynov

p.270 20.33

Subfamily Limnephilinae Anabolia Stephens Arctopora Thomson Asynarchus McLachlan Chilostigma McLachlan Chilostigmodes Martynov* Chyranda Ross Clistoronia Banks Clostoeca Banks Desmona Denning

p.270 20.3 20.4 20.5 20.6 p.271 20.7 20.8 20.9 20.11 11

Classification Frenesia Betten & Mosely Glyphopsyche Banks Grammotaulius Kolenati Grensia Ross Halesochila Banks Hesperop/zylax Banks Homophylax Banks Hydatophylax Wallengren Lenarchus Martynov Leptophylax Banks* Limnephilus Leach Nemotaulius Banks Phanocelia Banks Philarctus McLachlan Philocasca Ross Platycentropus Ulmer Psychoglypha Ross Psychoronia Banks Pycnopsyche Banks Sphagnophylax Wiggins & Winchester Apataniidae Allomyia Banks Apatania Kolenati Manophylax Wiggins Moselyana Denning Pedomoecus Ross

p. 190 12.1 12.2 12.3 12.4 12.5

Uel10idae Subfamily Uenoinae Farula Milne Neothremma Dodds & Hisaw Sericostriata Wiggins, Weaver & Unzicker

p.413 p.413 26.1 26.3 26.5

Subfamily Thremmatinae Neophylax McLachlan Oligophlebodes Ulmer Goeridae Subfamily Goerinae Goera Stephens Goeracea Denning Goerita Ross Subfamily Lepaniinae Lepania Ross

12

20.16 20.17 20.18 20.19 20.20 20.21 20.22 20.23 20.25 p.271 20.26 20.27 20.29 20.30 20.31 20.32 20.34 20.35 20.36 20.37

p.414 26.2 26.4 p.226 p.226 16.1 16.2 16.3 p.226 16.4

Classification Leptoceroidea Leptoceridae Subfamily Leptocerinae Ceraclea Stephens Leptocerus Leach Mystacides Berthold Nectopsyche MUller Oecetis McLachlan Setodes Rambur Triaenodes McLachlan Ylodes Milne

p.249 p.250 19.1 19.2 19.3 19.4 19.5 19.6 19.7 19.8

Molannidae Molanna Curtis Molannodes McLachlan

p.352 21.1 21.2

Calamoceratidae Anisocentropus McLachlan Heteroplectron McLachlan Phylloicus MUller

p.218 15.l 15.2 15.3

Odontoceridae Subfamily Odontocerinae Marilia MUller Namamyia Banks Nerophilus Banks Parthina Denning Psilotreta Banks

p.359 p. 360 22.l 22.2 22.3 22.4 22.6

Subfamily Pseudogoerinae Pseudogoera Carpenter Sericostomatoidea Sericostomatidae Agarodes Banks Fattigia Ross & Wallace Gumaga Tsuda

p.360 22.5 p.404 25.l 25.2 25.3

Beraeidae Beraea Stephens

p.203 13.1

Helicopsychidae Helicopsyche von Siebold

p.237 17.l

13

Biological Considerations

ANCESTRAL HABITAT

All three subordinal groups of Trichoptera are represented in cool, running waters (Fig. I). In families represented in both lotic and lentic waters, the genera with more primitive morphological character states occur in cool, lotic habitats, and those with derived states occur in warmer lentic sites (Ross 1956). The closed cocoons of spicipalpian families represent ancestral construction behaviour shared with primitive Lepidoptera (Wiggins and Wichard 1989). From the preponderance of Spicipalpia in running waters, it is inferred that these families are physiologically constrained to cool, lotic waters, where respiration of the pupae is sustained solely by the diffusion of oxygen across the osmotically semipermeable wall of the cocoon. Of the four families in the Spicipalpia, the Rhyacophilidae, Hydrobiosidae, and Glossosomatidae occur in flowing water; a few genera of the Hydroptilidae occur in lentic sites of lakes, but most genera, including the primitive members of that family, are confined to running waters. Accordingly, cool, lotic waters are inferred to be the ancestral habitat in which progenitors of the Trichoptera first became aquatic, and the habitat in which differentiation into the subordinal groups probably occurred. These groups represent essentially different methods of living and feeding by larvae, and it is likely that their differences evolved as innovations for exploiting available niches in lotic habitats. A common observation is that apart from Diptera, the Trichoptera are usually more numerous in species and more diverse biologically in a given lotic habitat than are other aquatic insect orders; this is an indication of the effectiveness of basic ecological diversification in the Trichoptera (Wiggins and Mackay 1978). Utilization of silk by caddisfly larvae for construction was undoubtedly an asset in their ecological diversification because silk adds, in effect, a whole new dimension to behavioural evolution; the situation is analogous to the role of silk in the ecological diversification of spiders. HABITAT DIVERSITY

It will be seen from Figure I that North American families of Trichoptera differ markedly 14

,

Biological Considerations in the ability of their members to exploit warm, lentic habitats: thus, all 26 North American caddisfly families (100%) are represented in cool, running waters; 21 (81 %) in warm, lotic sites; 8 (31 %) in standing waters of lakes and marshes, excluding those lotic-dwelling families whose larvae also live along wave-washed shores of lakes (i.e. Glossosomatidae, Hydropsychidae, Sericostomatidae, and Helicopsychidae); and only 3 families (11 %) in temporary pools, a habitat that for caddisfly larvae is a more constraining extension of permanent, lentic waters. We see then that representatives from all three subordinal groups of Trichoptera have invaded lentic waters independently, and that certain of the Integripalpia and Annulipalpia have further succeeded in colonizing temporary pools. In Figure r the gaps between habitat categories represent zones of intergrading conditions. Therefore, this series of habitat types grades through decreasing water currents and increasing water temperatures; current is critical in shortening the diffusion path by which oxygen becomes available for respiration by caddis larvae (Jaag and Ambuhl 1964). Consequently, the general trend of the series of habitat types in Figure r indicates increasing selection for greater respirational efficiency. If enhanced respirational efficiency is one of the requirements for caddisfly larvae living in lentic waters, it can hardly be coincidence that in five of the eight families represented in lentic waters, the larvae are portable-case makers: Leptoceridae, Molannidae, Phryganeidae, Limnephilidae, and Lepidostomatidae. The exceptions are the Dipseudopsidae, Polycentropodidae, and Hydroptilidae; and larvae of lentic-dwelling genera in each of these families construct tubular retreats or cases which the larva ventilates (see below). RESPIRATION

The idea that the portable tube-case of Trichoptera enhances respiratory efficiency has been shared by students of these insects at least since Dodds and Hisaw (1924) and Milne (1938), and possibly others before them. The principle is that dorsoventral abdominal undulation or ventilation by the larva brings a current of water through the anterior opening and out the posterior opening, a flow that can be detected readily by an observer (Fig. II); thus abdomen and gills are bathed in a current of continually renewed water. The tubular case serves then as a conduit for a channelled flow of water, enabling the larva to control its own current. In accordance with this hypothesis, the three humps of abdominal segment I are believed to maintain a space between the larva and the sides of the case, allowing the respiratory current access to all sides of the abdomen. It should be added here that at least some larvae can reverse the direction of water flow (Tindall 1963; Merrill and Wiggins 1971). Supporting evidence for the respiratory advantage of the tube-case has come from several sources. Jaag and Ambuhl (1964) found that larvae of the limnephilid genus AnaboZia, when inside their cases, were able to survive at lower oxygen concentrations than those without cases because they were able to remove more oxygen from the water. Several workers have shown that a rise in temperature or a decrease in dissolved oxygen results in an increased rate and amplitude of ventilatory movement by case-bearing caddisfly larvae (Van Dam 1938; Fox and Sidney 1953); Feldmeth (1970) found that in two species of Pycnopsyche the rate of ventilation increased as current speed decreased, indicating that abdominal ventilation compensates for low current velocity. Philipson (1954) 15

Biological Considerations Coollotic

Warm lotic

Lentic

Temporary pools

SPICIPALPIA (closed-cocoon makers)

Glossosomatidae Hydrobiosidae Hydroptilidae Rhyacophilidae

J

ANNULIPALPIA (fixed-retreat makers)

Dipseudopsidae Ecnomidae Hydropsychidae Philopotamidae Polycentropodidae Psychomyiidae Xiphocentronidae INTEGRIPALPIA (portable-case makers)

Apataniidae Beraeidae Brachycentridae Calamoceratidae Goeridae Helicopsychidae Lepidostomatidae Leptoceridae Limnephilidae Molannidae Odontoceridae Phryganeidae Rossianidae Sericostomatidae Uenoidae Decreasing current and 02 availability, increasing temperature

I

16

Habitat diversity in families of North American Trichoptera

,

,

Biological Considerations

Circulation of water generated by abdominal ventilation through case of typical case-making caddis larva II

demonstrated that the frequency of ventilation movements in Hydropsyche instabilis and Polycentropus jlavomaculatus decreased with increasing current. Larvae of rheophilic genera such as Rhyacophila and Wormaldia do not normally ventilate by abdominal movements (Philipson 1954), although under respiratory duress larvae of these two families and of the Glossosomatidae are said to ventilate (Tomaszewski 1973). Measurement of oxygen uptake by larvae with cases and deprived of their cases by Williams et al. (1987) showed that the case seemed to aid respiration in species of seven families because the rate of respiration was lower and less variable when the larva was in its case, or the case enabled the larva to tolerate lower levels of oxygen before dying. Larvae of two species, Helicopsyche borealis (Helicopsychidae) and Phryganea cinerea (Phryganeidae), consumed more oxygen in the case than they did without a case. For larvae of a third group, all belonging to the Limnephilidae, the case seemed to make little difference because oxygen consumption was the same with or without the case. Other species of both the Limnephilidae and Phryganeidae were represented in the first group of seven families where the case was an asset in respiration. Taken all together, these lines of evidence indicate that the most rheophilic caddis larvae are dependent upon stream current for renewal of freshly oxygenated water, and less rheophilic larvae, primarily Integripalpia, can create or control their own current by 17

Biological Considerations abdominal ventilation within their portable cases at rates geared to acquire the necessary oxygen with the lowest energy expenditure. Whether all larvae conform to this pattern remains conjectural. Under experimental conditions larvae of Oligotricha (Phryganeidae), Anabolia and Halesus (Limnephilidae) can survive and develop without cases for several weeks (Majecki and Tomaszewski 1991). Some lentic limnephilid species have been observed to abandon their case at low oxygen concentrations (Otto 1976, 1983). Interpretation of observations on the respirational efficiency of caddis larvae must take account also of the role of cases in protection against predators; efficiency of respiration within the case may be compromised by the need for the protection of portable cases, with the balance measured by survival in nature. Moreover, little is known about the respiratory requirements of pupae. Although the Annulipalpia are mainly rheophilic, some members of the Polycentropodidae are tolerant of lentic waters (Fig. J). Some species of Polycentropus, for example, live on lake bottoms where there are chironomid larvae that possess haemoglobin as a respiratory asset; and some Polycentropus live in temporary pools, where larvae make a fixed tubular retreat of silk (Fig. 9.50) which they ventilate by abdominal undulation (Wiggins 1973a). Larvae of Dipseudopsidae (Phylocentropus) construct extensive systems of tubes (Fig. 5.lD) in sandy substrates of streams and lakes, and generate a current through the tube. Since larvae of a few Hydroptilidae (Spicipalpia) occur in lentic waters and ventilate in the normal way, it is clear that the hydroptilid purse-case with its apical slits can serve also as an effective tubular conduit for a respiratory current. Among Nearctic hydroptilids, species of Oxyethira probably occupy the most lentic habitats; their cases are not the typical purse with slits, but a derivative flattened flask of silk with openings confined to front and rear (Fig. 3.12F). One may wonder to what extent the ability of these larvae to exploit lentic waters is correlated with more tube-like constructions. Even though these families differ biologically in many ways, the means by which their members have adapted to lentic waters are similar in principle; thus, the basic caddisfly larval tube, either portable or fixed, can be regarded as a device that for some and perhaps most families has increased respirational efficiency, thereby helping to open len tic habitats to exploitation by these insects. It is altogether remarkable that an increase in respirational efficiency has been achieved as a consequence of silk production. Notwithstanding a role in respiration, the portable cases constructed by larval Trichoptera probably served initially to protect and conceal larvae from predators. This seems self-evident because most caddis larvae that graze on diatoms and fine particulate matter on the upper exposed surfaces of rocks in flowing waters construct portable cases or fixed tubes. Larvae feeding on coarse detritus such as leaves would be exposed to predators as they moved to areas of slower current where these materials are usually deposited, and would benefit from the protection of a portable case. One would expect that some selective advantage for living in depositional areas would accrue to lotic larvae with more efficient respiration; thus, the portable case that initially afforded protection could have served a second role in enhancing respiration. With the means to enhance respiration independently of stream current, case-making Integripalpia could have exploited standingwater systems. Consequently, the two competing hypotheses proposed to explain the function and evolution of portable cases in Trichoptera (e.g. Williams et al. 1987) need not be 18

Biological Considerations contradictory. Protection of larvae from predators can be granted a primary role for portable cases; enhancement of respiratory efficiency would have followed as a further evolutionary dividend from the case, and seems to have been an asset in exploiting standing waters. FEEDING

Among the Spicipalpia, most larvae of the free-living Rhyacophilidae and Hydrobiosidae are predators, but not entirely so for some Rhyacophila are herbivorous (Thut 1969). The flat-bottomed, tortoise-like, portable cases of the highly rheophilic Glossosomatidae cover the larvae entirely as they graze diatoms and fine organic particles on the exposed upper surfaces of rocks. All three thoracic legs in glossosomatid larvae are approximately the same size (Fig. I.4A), as they are in the Rhyacophilidae and in the Annulipalpia, a condition that can be considered part of the trichopteran ground-plan. But in some of the Hydroptilidae and in all of the Integripalpia, the legs are progressively longer from front to rear; and except for highly specialized swimmers such as Leptocerus, these larvae are generally adept at walking with the last two pairs of legs (Tomaszewski 1973). Therefore, for feeding, the significance of portable cases - of tortoise, purse, or tube design - is that larvae are able to move actively in search of energy resources. Many of the Hydroptilidae became specialized for feeding on filamentous algae, although a few groups feed on periphyton and fine organic particles. In the Integripalpia, development of respirational independence probably has allowed the exploitation of food unrelated to current. Many genera, particularly in the Limnephilidae and Lepidostomatidae, became largely dependent on dead plant materials such as leaves and wood fragments which support growths of fungi and bacteria; the micro-organisms have much to do with the palatability and nutrient value of these materials (e.g. Biirlocher and Kendrick 1973, 1975). Larvae feeding in this way are shredders (Cummins 1973), fulfilling one of the most important ecological roles in fresh waters, for in this manner leaves and other large pieces of plant materials are reduced to the fine organic particles utilized by collectors. A few of the Integripalpia - some Phryganeidae, Oecetis, and Ceraclea - became predators; some became diatom feeders as in the Apataniidae, Uenoidae, and Goeridae. Information available to date suggests that omnivorous feeding is the general condition for larvae in most families of the Integripalpia. Larvae of the net-spinning Annulipalpia (Philopotamidae, Hydropsychidae, and some Polycentropodidae) build a fixed retreat in which the larva lies while food particles of appropriate size are collected from the current by its silken capture net. In a functional sense, these retreat-makers are filter feeders (Cummins 1973), and their food includes small fragments of plant and animal materials, faeces of other invertebrates with associated fungi and bacteria, algae, and in some instances other invertebrates. Food of the Philopotamidae is very fine particulate materials; larvae of some genera of the Polycentropodidae are highly predacious. In the Psychomyiidae, Xiphocentronidae,and Ecnomidae, detrital particles, associated microflora, and algae are also collected, but largely from the substrate surface. These aspects of feeding are summarized in Table 1, based on, but amplifying for Trichoptera, the classification of trophic categories for aquatic insects developed by Cum19

,

,\

Biological Considerations TABLE I Classification of trophic categories for North American Trichoptera (based on Cummins 1973) Method of feeding Shredders

Collectors

Dominant food Herbivores . feeding on living vascular hydrophytes and filamentous algae

Filter or , suspensIOn feeders

North American Trichoptera Brachycentridae (Eobrachycentrus, Micrasema) Hydroptilidae (Hydroptilinae) Leptoceridae (Triaenodes) Phryganeidae

Detritivores feeding on pieces of decomposing vascular plant tissue and associated microflora

Beraeidae Calamoceratidae Lepidostomatidae Limnephilidae Odontoceridae Phryganeidae Sericostomatidae

Detri tivoreherbivores feeding on fine organic particles and living algal cells

Brachycentridae (Brachycentrus) Di pseudopsidae Hydropsychidae Philopotamidae Polycentropodidae (Neureclipsis)

, !

,

•

Substrate surface feeders Scrapers

As above

Herbivoredetritivores feeding on periphyton and fine organic particles

Brachycentridae Leptoceridae Psychomyiidae

J

Glossosomatidae Helicopsychidae Hydroptilidae (Leucotrichia) Leptoceridae Apataniidae Goeridae Molannidae Limnephilidae (Dicosmoecinae)

(

,,

Predators

Carnivores feeding on whole animals or large parts

,

Hydropsychidae Leptoceridae (Ceraclea, Oecetis) Molannidae Phryganeidae Polycentropodidae (Nyctiophylax, Polycentropus) Rhyacophilidae

, •

1 20

)

Biological Considerations mins (1973). This must be seen only as an overview; several families appear in more than one category on the basis of different genera, although the generic examples listed are not complete for a given family. The food of some species changes seasonally or as the larvae grow larger; Banksiola crotchi became almost totally predacious in the final instar after feeding on detrital materials up to that point (Winterbourn 1971b). Probably because they are limited by small physical size, early instars in all trophic groups feed on fine particulate organic matter. Analyses of food ingested by larval Trichoptera reveal a strong tendency for opportunistic feeding within single species; one example is the finding by Cummins (1973) that larvae of Glossosoma nigrior fed largely on periphyton in a Pennsylvania stream but on detritus in a Michigan stream. Trophic generalism is, in fact, the pattern of feeding by aquatic insect larvae over all (Cummins 1973). For Trichoptera, the central point emerges that, in evolution leading to marked divergence in ways of obtaining food, there has been little restrictive specialization in the kind of food that can be utilized. CONSTRUCTION BEHAVIOUR

Retreats and cases are constructed by larvae in some groups of beetles and moths, but the diversity of these structures is much greater in the Trichoptera than in any other order of insects. Trichoptera are favourable subjects for studying behaviour because they provide a tangible record of what they do; analysis of construction behaviour in the Trichoptera on a detailed level has been undertaken by several workers, such as Hanna (1960) and Hansell (1972,1974). Although lhe cases and retreats built by larval caddisflies are extremely important in respiration and feeding, consideration of their structural details in relation to micro-habitat is illuminating in other respects. For the most part these structures are lined with silk, and plant and rock pieces are incorporated on the outside. But one can find examples of ways in which this basic behaviour has evolved to solve many engineering problems: streamlining, ballast, buoyancy, structural rigidity, camouflage, internal water circulation, external water resistance, regulation of mesh size in nets to obtain an effective compromise between current speed and fine-particle filtering, protection from predators that would swallow the case and from those that would intrude, and so on. Solutions to some of these problems in relation to rapid currents were explored by Dodds and Hisaw (1925); comments on others are offered in appropriate places in the systematic part of the present work. Again, the significance of silk production in increasing the diversity of solutions, and hence of niches exploited, is clear. Construction of retreats, often integrated with silken filter nets, has contributed to the ecological, and hence taxonomic, diversification of the Annulipalpia (see, e.g., Wallace 1975a, b; Wallace and Malas 1976b). Although the Integripalpia reveal considerably more taxonomic diversity than do the Annulipalpia, the contribution of different SOltS of portable cases as factors underlying ecological and taxonomic diversity in this group is scarcely understood (e.g. Wiggins 1984b). The ability of caddisfly larvae to recognize and re-enter their own cases was found by Merrill (1969) to differ considerably in several families of Integripalpia; she also found that sensors on the anal claws are important in regulating the maximum length to which a case is built (Merrill 1965). The idea, often repeated, that caddisfly species can be distinguished by the cases they 21

Biological Considerations build has only slight support. By and large, case architecture is characteristic at the generic level. If in a particular area a genus is represented by only one species, the case is likely to be of diagnostic value; but where several congeneric species are sympatric, case types are generally not diagnostic for the species. Pupation, the final phase of aquatic existence in the life cycle, introduces a new set of environmental problems. For the most part, these problems represent compromises between protection of the resting pupa from predators, and sufficient exposure of the pupa to oxygenating currents of water for respiration. Again, the problems have been met by different ways of using silk to construct pupal enclosures and cocoons (Wiggins and Wichard 1989; Wichard 1991; Frania and Wiggins 1995). LIFE CYCLES

Most caddis flies in temperate latitudes complete one generation each year, passing through the egg, five larval instars, a pupal stage, and a winged adult stage; the time required for completion of the actual metamorphosis - that is, from separation of the larval cuticle to eclosion or emergence of the adult from the pupal integument - is approximately three weeks. This is the generalized condition, characterized by uninterrupted development. In distinction from many other biological characteristics of Trichoptera, most of the modifications imposed on this generalized condition are a feature of the species rather than the genus. A life cycle of six larval instars was recorded for a European species of Sericostoma (Elliott 1969) and of seven for a European Agapetus (Nielsen 1942); larvae of Gumaga lIigricula studied in California moulted up to 14 times during their development (Resh et al. 1981). Some modifications to the generalized condition arise through intervention of diapause - a suspension of normal development at some stage in the life cycle until initiated again in response to an external environmental stimulus. Diapause is distinguished from simple quiescence, in which development merely slows during adverse, usually cold, periods to be resumed when conditions again become favourable. For Trichoptera, diapause functions as for other insects by suspending development until conditions in a habitat are more favourable, and also by synchronizing adult emergence after dissimilar periods of larval development. In the family Limnephilidae diapause occurs in both larval and adult stages (e.g. Denis 1978). Diapause was demonstrated in the last larval instar of the European limnephilid species Anabolia furcata (Novak 1960): larvae were fully grown in June, fastened their cases to the substrate, and ceased feeding. Experiments revealed that diapause was terminated by short daily photoperiods, similar to those occurring naturally in late summer. Pupation occurred in nature in September, adult emergence commencing toward the end of that month. Some influence was also attributed to temperature in termination of the diapause, with temperatures lower than 20°C hastening termination; adults were found to emerge earlier at higher elevations than those of the same species at lower elevations. Novak suggested that diapause in the last larval instar was a general condition for univoltine autumnal Trichoptera. One, and perhaps the principal, advantage of autumnal reproduction is that larvae feeding on fallen leaves of deciduous trees have a particularly rich food resource in autumn and early winter; larval development completed in winter or early

22

,,

\

Biological Considerations spring must then be suspended until autumn approaches again. The same principle probably holds for the Nearctic limnephilid genus Pycnopsyche; although diapause has not been demonstrated, inactivity of final-instar larvae for periods up to six months, followed by initiation of metamorphosis during the decreasing daily photoperiods of late summer (Cummins 1964; Mackay 1972), suggests that diapause is operating as in Anabolia furcata. Similarly, larval feeding and growth in most species of Neophylax are completed in spring or early summer, when larvae fasten their cases firmly to the substrate and seal off the entrance. Larvae remain within the case for several weeks, and metamorphosis occurs in late summer followed shortly after by adult emergence (Beam and Wiggins 1987). Most species of the limnephilid genus Dicosmoecus show a similar pattern (Wiggins and Richardson 1982). Synchronization of adult emergence may also be an advantage in these instances; species of both genera are autumnal for the most part and, perhaps as a consequence of lower temperatures at night, the adults are largely diurnal in activity. Daytime activity of caddisfly adults is found in relatively few species of Trichoptera over all, and there seems a reasonable possibility that when it does occur, synchronized emergence of adults might help to compensate for the greater hazards of diurnal reproductive activity. For some Neophylax that live in streams of temporary flow, larval diapause serves to postpone oviposition until after summer drought (Wiggins 1973a). Diapause in the adult stage is advantageous for species of the Limnephilidae and Phryganeidae inhabiting temporary pools (Novak and Sehnal 1963, 1965; Wiggins 1973a); sexual maturity of adults emerging in spring is delayed until late summer, when development is resumed, largely through the stimulus of shorter daily photoperiods. This postponement of oviposition places eggs in the pool basins in autumn when the moisture level of surface soil is being replenished, thereby avoiding the summer drought. Embryonic development proceeds and larvae break out of the egg chorions but can remain in the gelatinous egg-matrix for several months, even until spring, when flooded by surface water in the pool basin (Wiggins 1973a). In this way, diapause in the adult brings about the initial delay in the life cycle, and larval development can coincide with the occurrence of temporary autumnal pools. However, the additional delay required for larvae to exploit temporary vernal pools appears to be facilitated by the more stable nature of the gelatinous egg-matrix and by the tendency of the larvae to remain within the matrix until the stimulus of sUlface water is received in spring. There is some evidence that small amounts of surface water can provide sufficient stimulus for larvae to leave the matrix and build cases in the autumn. Final-instar larvae in some species of the limnephilid genus lronoquia aestivate in unsealed cases around the edge of temporary pools and streams during summer periods of declining water levels, with metamorphosis taking place in late summer (Flint 1958; Williams and Williams 1975). Although photoperiod control has not been demonstrated, it seems likely that this situation differs from the preceding one only in the imposition of diapause on the last larval instar rather than the adult; the advantage in avoiding the summer drought period of temporary waters is the same. Diapause of eight to nine months was reported in the eggs of Agapetus bifidus in Oregon (Anderson and Bourne 1974). This may be the mechanism by which other species of Agapetus are able to populate temporary streams, as reported in Illinois by Ross (1944). 23

Biological Considerations Life-cycle modification leading to accommodation of congeneric species in the same habitat appears to be operating in Neophylax. Most species of this genus have autumnal emergence, but adults of the eastern N. ornatus emerge in spring. Life-history data compiled by Mackay (1969) reveal that larval feeding of this species occurs from summer through to December; larvae of N. nacatus, an autumnal species in the same habitat, feed during winter and spring. Coexistence of species of Pycnopsyche in the same general habitat is accommodated through differences in their life history, behaviour, and feeding (Cummins 1964; Mackay 1972). Although the univoltine life cycles described above are the usual condition in Trichoptera, some species are known to be bivoltine or even trivoltine. Some species of Hydropsyche in Ontario, for example, have a fast-growing summer generation of larvae maturing in July or August and a slow-growing winter generation of larvae maturing in April or May (Mackay 1979). Growth rates increased by high summer water temperatures and food quality raised the probability that a summer generation could mature before fall. Then there could be two overlapping generations per year as reported for Glossosoma penitum in Oregon (Anderson and Bourne 1974). Larval populations of Ceraclea transversa were found in two cohorts in Kentucky (Resh 1976); one overwinters in the last larval instar with cases sealed in preparation for metamorphosis and emerges in spring, and the other overwinters in the third or fourth instar and emerges in summer. By contrast, larvae of some species in the Odontoceridae, Calamoceratidae, Beraeidae, and Limnephilidae evidently require more than one year to complete a cycle; this is a difficult point to interpret, for in addition to collection of specimens representing a broad span of developmental stages at the same time, one also needs to have some information about the length of the adult emergence period. These are some examples of deviations from the generalized life cycle. All of them have come to light in recent years, and it is likely that we have much to learn about how very diverse the life cycles of caddisflies really are. The final point to be discussed under life cycles concerns the term prepupa. This term has been widely used by workers on Trichoptera for the interval from the time when the pupal case is fastened to the substrate and the anterior and posterior openings are sealed off, to the time when larval-pupal ecdysis occurs, that is, the point at which the external form of the insect changes from larva to pupa. But used in this sense, as Hinton (1971) has pointed out, the term prepupa covers several biological stages and events: (a) the larva sealed within the pupal case in a resting condition for intervals from several days to several months in genera such as Neophylax, pycllopsyche, and Dicosmoecus; (b) larvalpupal apolysis in which the larval cuticle is separated from the pupal epidermis; and (c) the pupa when histological reorganization of metamorphosis is taking place within but not connected to the larval cuticle. These events are terminated by larval-pupal ecdysis, when the larval exuviae are cast off and the newly formed cuticle beneath gives the insect the typical pupal form. As knowledge of the biology of Trichoptera increases, especially such aspects as the operation of diapause, it becomes necessary to identify more precisely the stages at which certain events occur. Thus, in the present work, the term prepupa is restricted to the period (a) above, when the larva is in a resting condition, because it establishes that the functional larva is closed off within the pupal case, and that feeding has terminated. 24

, I

\

Biological Considerations Larval-pupal apolysis, (b) above, tenninates the prepupal stage and marks a significant change because functionally the insect is no longer a larva but a pupa. Larval-pupal apolysis in Trichoptera can probably be detected well enough for practical purposes from certain external changes: in the majority of families the middle and hind legs change from the normal active position in which they are partially bent and directed anteriorly to a more or less distorted position in which they become straightened and directed toward the posterior end of the insect; and in all families the eyes and the muscles of the legs and other parts no longer coincide with their position in the overlying larval cuticle. The term pharate pupa (Gr. pharos, a garment) is used to designate the period, (c) above, when the developing pupa is enclosed within the detached larval cuticle (Hinton 1971). This phase of development is tenninated by larval-pupal ecdysis. When a caddisfly leaves the pupal case to come to the surface for eclosion or emergence from the pupal cuticle, it is functionally an adult, and from the time of pupal-adult apolysis it is termed a pharate adult (Hinton 1971). The mandibles of caddisfly pupae are, in fact, moved by muscles of the adult, and the oar-shaped legs of the pupal cuticle are powered by the slender legs of the adult which lie beneath (Hinton 1949).

25

Morphology

,,

Morphological terms of a general nature can be found in an entomological text or glossary. Those that have particular application to the Trichoptera are explained here and illustrated in Figures III-VI. Morphological structures of larvae in many of the same genera occurring in Russia were illustrated by Lepneva (1964, 1966). A distinction between spines and setae should be made at the outset. Spines are extensions or processes of the cuticle; they may be short and pointed, longer and blade-like, comb-shaped, or of some other form. Spines are one type of surface sculpturing, and as an integral part of the cuticle, they are retained on the exuvial sclerites after ecdysis; it is likely that spines are largely protective in function. Setae are innervated sense receptors; they arise in alveoli or pits in the cuticle and range widely in size to include stout bristles, flattened scale-setae, and spurs. Setae are articulated cuticular appendages, and usually become separated from the exuviae at ecdysis, leaving the pit to mark their position, although some pits hold sensory receptors which lack setae. Varying distribution of setae and pits provides important taxonomic information for larvae in the sister order Lepidoptera; a comprehensive system of chaetotaxy in Trichoptera has been proposed (Williams and Wiggins 1981). HEAD

Sclerites of the head capsule include a parietal on each side of the head (Fig. HIE), and the two parietals are in contact dorsally along a median coronal suture (Fig. IlIA); between the parietals dorsally is the Jrontociypeal apotome, separated from them by the Jrontociypeal

Morphology of caddisfly larvae. A, head and thorax of a limnephilid, dorsal, sal =setal area 1, etc.; B, labrum of a limnephilid, dorsal, primary setae numbered; c, head of a limnephilid, dorsal, primary setae numbered; D, head of a limnephilid, ventral, primary setae numbered; E, head of a limnephilid, lateral; F, gular area of head of a diplectronine hydropsychid, ventral

III

26

Morphology labrum,

A

3 frontoclypeal , apotome

,

, antenna

B

c o

J

-----------pronmum

o o

()

mid-dorsal - - - - - - - - ecdysial line

- - - - - - - - mesonotum

sa1

cardo ventral apotome

sa2

D

-

sa3

\

sa1

I

sa2

- - - metanotum

anterior ventral apotome , ,

parietal

eye/stemmata ,

,

, frontoclypeal apotome , . ,

F

,antenna ventral ecdysial line - -

E postgena occipital margin

- - labrum - - - mandible - - maxilla - - - labium posterior ventral apotome

27

Morphology sutures (Fig. IlIA). The coronal and frontoclypeal sutures together fonn the Y-shaped dorsal ecdysial lines along which the head sclerites separate at ecdysis (Fig. IlIA). Ventrally the genal areas or genae of the parietals are separated along the median line by the ventral apotome (gular sclerite) which may separate the genae completely (Fig. IlID)or only partially, either as a single sclerite or as two - the anterior and posterior ventral apotomes (Fig. IlIF). At ecdysis the parietals separate ventrally along the ventral ecydsial line (Fig. IIIF). The exterior surface of the head capsule is often roughened by spines, ridges, or various types of sculpturing; on the interior, but often visible from the exterior, are round spots or muscle scars at attachment points for muscles of the head. The labrum is hinged to the anterior edge of the frontoclypeal apotome, and frequently bears a membranous anterolateral fringe (Fig. l2.2B, E). The eyes, strictly speaking, are clusters of stemmata (Fig. IlIE), but the tenns are used interchangeably here. Antennae in most Integripalpia, Glossosomatidae, and Hydroptilidae are rod-like and usually short (Fig. IIIE), but much longer in most Leptoceridae and some Hydroptilidae; in the Annulipalpia, Rhyacophilidae, and Hydrobiosidae antennae are small and not clearly differentiated (e.g. Fig. 8.3B). Primary setae ofthe head and labrum are usually stable in position and are numbered (Fig. IllB, c) in accordance with the system proposed by Nielsen (1942); setae 8 and 18 arise on the ventral surface of the head (Fig. lIID). Secondary setae sometimes occur on the dorsum of the head as in Figure 12.2F. Mouthparts (Fig. VIB) are identified by standard tenns. The silk produced by caddisfly larvae is emitted through a small orifice at the tip of the labium; labial palpi are absent in some families, submental sclerites differ widely in shape and sometimes are fused. On the maxilla adjacent to the labium is a rounded lobe (Fig. VIB), or a slender finger-like process (Fig. 4.2B), bearing sensilla; differing views as to whether this structure is correctly interpreted as galea or lacinia have been summarized by Matsuda (1965), who concluded that in Trichoptera it is mainly a fusion product of the two, which can be tenned the maxillary lobe. Structures identified in Figure VIB as carda, stipes, palpifer, palpiger, and mentum are identified primarily by the sclerites borne on these parts. Mandibles have cutting edges of two basic types, evidently correlated with feeding behaviour - a series of separate points or teeth (Fig. 12.4D), or an entire, scraper-like edge (Fig: 12.3D) - and are articulated with the head capsule by means of a knob-like ventral condyle and a dorsal cavity. The blades of scraping mandibles which occur in larvae that graze periphyton from rock surfaces are worn down through constant abrasion against mineral substrates (Arens 1990, fig. 11); consequently, these mandibles change in shape through each instar (e.g. Wiggins and Richardson 1982, figs. 31, 32). THORAX

The pronotum is always covered by two heavily sclerotized plates closely appressed along Morphology of caddisfly larvae, illustrated by generalized limnephilids. A, entire larva, lateral, abdominal segments numbered I-X; B, abdominal segment I, dorsal; c, abdominal segment I, ventral; D, abdominal segment bearing branched gills, lateral; E, forked lamella enlarged in face view and in profile, approx. x470; F, detail of bifid filaments of the lateral fringe IV

28

Morphology antenna - - - - - - - - - - - - - -,

A B lateral hump seta ,

dorsal hump - -

o ~ _-_- j

-

Y '"

- - - - - -lateral hump seta

- -- --

--

lateral hump

c

d r

lateral fringe - - - - - - - - - :

- - - ; single tracheal gills , , , ,

lateral, fringe ,

1

,

/;

l l,,···

branched tracheal gill ,

. I

.:' '_-

i 0'--"& , ' .

,

o ~j

,

,

,

,

, , ,

--

~

·······-·l··~··

......

I

1

. . !q I

j

VI

d"

~,'-'.

V .1

~l

,~

,~~,.

.

,

, ' chloride epithelia

A

)0

I forked lam~lIa I

I

I

\ \ \

o

\

, bifid lateral filaments ,

F

't;r=i IX

dorsal sclerite - - - - - - - -

E (in profile)

"

'll X anal proleg - - - - - - -

,/1

29

Morphology the mid-dorsal ecdysial line (Fig. lIlA); the prosternum frequently bears sclerites. In several of the case-making families (Integripalpia) there is a membranous, finger-like prosternal horn (Fig. VIA) of unknown function (e.g. Bicchierai and Moretti 1987). The trochantin (Fig. VIA), a derivative of the prothoracic pleuron, is shaped characteristically in different genera. The mesonotum may be largely sci erotized, and the plate entire (Fig. 3.16A) or variously subdivided by median or transverse ecdysial lines; or the mesonotum may be membranous and with or without small sclerites. In most of these conditions, mesonotal setae arise in three primary locations - setal area 1, sa2, and sa3 (Fig. IlIA); setae are variously modified in different genera and so numerous in some larvae that the primary setal areas cannot be distinguished (Fig. 14.SB). Arrangement of the sclerites and setae is of taxonomic significance. Sclerotization of the metanotumis variable; usually the sclerites are smaller than those on the mesonotum, but the setal areas have the same primary arrangement (Fig. IIIA). The pleuron of both the meso- and metathorax comprises an anterior episternum and a posterior epimeron separated by a darkened depressed line - the pleural suture (Fig. VIA). The mesepisternum is extended anteriorly in the Goeridae (Fig. 16.1B). The thoracic legs in some families are all approximately the same size, but in most the fore legs are shorter and their segments stouter. Legs (Fig. VIA) are variously armed with spines, combs, and setae; spurs are very stout setae, usually at the distal end of the tibia, and often paired. The basal seta of the tarsal claw is enlarged to spur-like proportions in some groups; the tibia and femur are secondarily subdivided into two parts in some genera. The distinction between major and minor femoral setae is based on overall length and thickness. The trochanter is usually divided into two parts; the trochanteral brush is a tuft of setae often present on the distal part. ABDOMEN

Segment I in most families of the Integripalpia bears a median dorsal hump and at each side a lateral hump (Fig. IVA); the humps are retractile and in specimens preserved within the case may be indistinct. On both dorsum and venter of segment I (Fig. IVB, c) setal areas corresponding to sal, sa2, and sa3 of the thoracic nota can be recognized. This is essentially the arrangement on segment I in such families as the Phryganeidae and Glossosomatidae, and underlies setal patterns in the Limnephilidae where the diverse arrangements of setae on segment I are of considerable taxonomic value. In some genera of the Limnephilidae it is not possible to distinguish between these setal areas (e.g. sal and sa2 in Fig. 20. 12D), a condition which for descriptive purposes I have usually inferred to be a result of amalgamation. The boundary between dorsal and ventral sets is usually a single seta (Fig. IVA, c), sometimes two (Fig. 20.33A), on the ventral part of the lateral hump, here designated the lateral hump setae. The lateral humps of segment I in several groups bear sclerites which are important taxonomically; since these sclerites are often lightly pigmented, they are best distinguished by a more rigid and shiny surface, and careful examination under good microscope illumination is necessary to distinguish them. Segment IX bears a dorsal sclerite (Fig. IVA) in some families, and the arrangement of 30

Morphology B

A

c

- - - - lateral sclerite - - - ventral sole plate

---

,lateral sclerite - - - - - - - anal claw

___ ventral sole plate

, accessory hook

anal claw basal tuft

--

",' - - - ventral sole plate

dorsal plate

,

D

dorsal plate

- - - dorsal sclerite, seg. IX lateral sclerite - - - - - - anal claw

, dorsal plate

basal tuft

v Morphology of anal pro legs of caddisfly larvae. A, a philopotamid, lateral; B, a Iimnephilid, lateral; c, a glossosomatid, lateral; 0, a goerid, dorsal, including segments VIII and IX setae on segments VII, VIII, and IX can be of taxonomic significance. Occasionally when the sclerite is not pigmented, it can be detected by the firm, shiny surface. The anal prolegs exhibit significant structural diversity, and homologies designated here for component parts are largely those proposed by Ross (1964). The' condition in Figure VA, from the Annulipalpia, is considered to represent the primitive type for the Trichoptera; in these retreat-making families and also in the free-living Rhyacophilidae, the anal prolegs are elongate, separate, and very mobile. Bridging the flexible membranous connection between the lateral sclerite and the allal claw is a slender dorsal plate and ventral sole plate. In the derivative condition seen in the Integripalpia (Fig. VB), it is inferred that the prolegs have become short and thick, their bases swollen (Fig. vo); short, stout prolegs enable the larva to grip the interior of its close-fitting tubular case with the anal claws, usually armed with stout accessory hooks. In most genera of the Integripalpia there is little evidence of a dorsal plate (Fig. VB), but a small sclerite incorporating the bases of the stout, terminal setae termed the basal tuft does occur in a few genera (Fig. vo), such as Goeracea (Fig. 16.2G) and Goerita (Fig. 16.30); in Lepania (Fig. 16.4G) a sclerite without setae occurs ventrolaterad of the basal tuft. Both types are interpreted here as dorsal plates. The G1ossosomatidae of the Spicipalpia (Fig. vc) are inferred to represent an intermediate condition in which some shortening of the proleg and reduction of the size of the anal cia w 31

Morphology

•

are evident relative to the condition of these structures in the Rhyacophilidae. The anal prolegs are interpreted in larval Trichoptera as derivatives of segment x; ten abdominal segments are recognized in adult Trichoptera, and also in larvae of the sister order Lepidoptera. The lateral fringe (Fig. IVA, D, F) is a line or band of fine filaments along each side of the abdomen in some families, principally of the Integripalpia; the filaments are bifid and usually hollow, but single filaments occur in Phylocentropus (Annulipalpia) and in some genera of the Hydroptilidae (Spicipalpia) (Kerr and Wiggins, in press). In many Integripal pia there is a row of tiny forked lamellae (Fig. IVD, E) on each side of some abdominal segments (Kerr and Wiggins, in press); elsewhere these have been termed bifid processes and lateral tubercles. In families of the Limnephiloidea, forked lamellae usually occur on most abdominal segments; in families of the Leptoceroidea and Sericostomatoidea, forked lamellae are almost always confined to segment VIII. Serrate lamellae, which may be homologous with forked lamellae, occur in larvae of Sericostomatidae, Helicopsychidae, and Beraeidae (Fig. 13.1 A). Respiratory exchange in Trichoptera occurs chiefly through tracheal gills which are filamentous extensions of the body wall. Gills are usually located on abdominal segments, although they are found on thoracic segments, too, in some families; in larvae of a few species gills are lacking entirely. Tracheal gills are single (Fig. IVA), or branched basally (Fig. IVD), or they occur as terminal or lateral branches from a central stalk as in the Hydropsychidae (Fig. 7.1A). The gills are arranged in definite positions in three horizontal series - dorsal, lateral, and ventral - on each side of most abdominal segments, with an anterior and posterior gill position in each series; a segment with a complete complement would have six gills on each side. Thus, the precise position of a gill on any given segment can be designated as anterodorsal, anterolateral, posteroventral, and so on. Arrangement of gills is significant taxonomically because some are often absent from particular positions, especially on the more posterior segments, but characters of gill arrangement are frequently variable and are also subject to change from one instar to another. Diagnostic gill characters offered in this study are based on final instars. Beneath the cuticle of each tracheal gill, fine tracheoles lie in the respiratory epithelium; Wichard (1973) showed in larvae of the Limnephilini that an optimum system for respiratory exchange was achieved by the arrangement of these tracheoles parallel to the long axis of the gill, with uniform intervals between tracheoles. Osmotic regulation in at least some families of Trichoptera is mediated through rectal papillae as it is for insects generally (Schmitz and Wichard 1978); this appears to represent the primitive condition for Trichoptera, but in the Phryganeidae larvae swallow water to provide an additional source of the chloride ions absorbed by the rectal papillae (Schmitz and Wichard 1978). In addition, however, ionic absorption for osmoregulation in several families of Trichoptera is also achieved through anal papillae (Niiske and Wichard 1971). These are elongate lobes arising from within the anal opening (Fig. 8.3A); anal papillae can be everted by pressure of the haemolymph and retracted by muscular action

Morphology of caddisfly larvae. A, thorax and metathoracic leg of a limnephilid, lateral; B, maxillae and labium of an apataniid, ventral

VI

32

.'

Morphology A

fore trochantin , , , , ~"'_ "-

173

10 Family Psychomyiidae

The Psychomyiidae are a small family widely distributed over much of the world. Four genera are recognized in the Nearctic region, with a total of about 17 species in Canada and the United States; representatives occur in most parts of the continent, at least one ranging as far north as the tree line. The larvae differ from those of the Polycentropodidae in several features. One character diagnostic for the Psychomyiidae is the broad, hatchet-shaped trochantin of the prothorax, which is separated from the propleuron by a well-marked suture (Fig. W.4C). The labium is extended well beyond the anterior margin of the head (Fig. 1O.3c), probably to facilitate application of silk to the interior of the dwelling tube; labial pal pi are absent. The maxillary lobe is broad and flattened, the submental sclerites usually paired and separate (Fig 1O.3C). The pronotum alone is sclerotized, and the fore legs stouter than those of the other se ents; tarsal claws are short, bearing a stout basal process with a long seta. The abdomen I ks the lateral setae of the Polycentropodidae, and anal papillae are usually present. The sal segment of the anal proleg is much shorter than the distal segment that bears the laterai sclerite, and the anal claw is well developed. Psychomyiid larvae construct tubes of silk covered with sand and debris on rock and wood substrates where they feed on periphyton. According to Nielsen (1959), the tube is moved slowly across the substrate as the larva breaks down one end and adds on to the other. In this way new grazing areas can be reached as those adjacent to the ends of the tube are depleted. For the most part, larvae live in cool, running water, but some TInodes live in isolated stream pools in western North America and along lake margins in Europe. This evidence of independence from stream current in TInodes is noteworthy because the larvae lack lateral abdominal setae, which might be an asset for larvae of Polycentropodidae in generating their own respiratory current. Available information indicates that psychomyiid larvae feed mainly on detritus and associated microflora (Lepneva 1964) and algae. There are two subfamilies in the Psychomyiidae, both represented in North America. The Psychomyiinae include Lype, Psychomyia, and Tinodes, and are widely distributed over the globe. The Paduniellinae are represented in North America only by Paduniella, but otherwise the subfamily is widespread in Asia and Africa. 174

.

.'•I,

•

10 Family Psychomyiidae Key to Genera* 1

2

•

Anal claw with well-developed teeth arising from ventral, concave margin (Fig. 10.3A)

2

Anal claw without teeth on ventral, concave margin (Fig. lO.4A)

3

(1) Ventral surface of labium with paired submental sclerites prominent and much

longer than wide (Fig. 1O.3c). Widespread

10.3 Psychomyia

Ventral surface of labium with paired submental sclerites smaller and wider 10.2 Paduniella than long (Fig. 1O.2c). Arkansas, Missouri 3

(1) Mandibles with prominent dorsolateral bump anterad of base, often larger on

one mandible, dorsolateral condyle mayor may not be prominent, pair of lateral setae arising near middle of each mandible (Fig. lO.4D); submental sclerites usually rather large, approximately half as long as wide. Western 10.4 Tinodes Mandibles lacking prominent dorsolateral bump, but small dorsal condyle located close to base, pair of lateral setae arising approximately one-third of distance from base of each mandible (Fig. 1O.1C); submental sclerites smaller, approximately one-third as long as wide (Fig. 1O.1D). Eastern 10.1 Lype

*See qualifications under Use of Keys, p. 7. 175

10.1 Genus Lype Several species of this genus arc known in Europe, but only a single species, L. diversa (Banks), occurs in North America; it is confined to the eastern half of the continent, extending as far north as Wisconsin, Ontario, Quebec, and Maine. Diagnostic characters at the generic level were given by Ross (1959) and Flint (1964a); the larva of L. diversa was described in detail by Flint (1959). DISTRIBUTION AND SPECIES

MORPHOLOGY The larva of Lype diversa is similar to that of the western genus Tin-

odes, and seems best distinguished by the structure of the mouthparts. In Lype there is no prominent dorsolateral bump on the mandibles as there is in Tinodes, although a small dorsal condyle is located close to the mandibular base (C); the paired lateral setae on each mandible are situated basad of the mid-lateral point (c). There arc two sctal brushes on the inner edge of the left mandible, and the mandibles are approximately as long as they are wide. The submental sclerites are smaller than in Tinodes, and approximately one-third as long as wide (D). Length of larva up to 8.5 mm. RETREAT Larval retreats of L. diversa (E) are exceedingly well camout1aged. A slightly

arched roof of silk and small pieces of detritus cover a depression in a piece of submerged wood, forming a chamber in which the larva is concealed. The retreat is open at each end. Length of retreat illustrated approximately 8 mm. BIOLOGY Larvae of L. diversa live in small, cool streams, where their retreats are usu-

ally constructed on submerged logs and branches. The retreat illustrated was found on small pieces of wood incorporated into the case of a living larva of Linmephilus. Larvae are believed to graze on fine organic patticles, and perhaps algae as well.

Nimmo (198) and Armitage and Hamilton (1990). A European species, Lype p/taeopa (Stephens), sho~s little change in male genitalic morphology from specimens preserved in Baltic amber from the upper Eocene epoch, some 50 million years in age (Ross 1958).

Lype diversa (South Carolina, Oconee Co., 17-18 May 1970, ROM 700347) A, larva, lateral x19, trochantin enlarged; B, head, pro- and mesonotum, dorsal; c, mandibles, dorsal; D, head, ventral; E, retreat, dorsal approx. x 12 176

\

I

psychomyiidae: Lype 10.1

c A

o

B

E

177

10.2 Genus Paduniella This genus is widely represented in Asia from India and the Far East of Russia to the Philippines and Indonesia, and also in Africa and southern France. A single species, P nearctica Flint, is known in North America but to date only in Arkansas and Missouri (Flint 1967d; Mathis and Bowles 1994). Identity of the larva of P nearctica has been established in the same Arkansas stream on which the type locality is situated (Mathis and Bowles 1994). DISTRIBUTION AND SPECIES

MORPHOLOGY Although the larva of Paduniella nearctica has prominent teeth on the

ventral margin of the anal claw (F) as in Psychomyia (Fig. 10.3), the submental sclerites (c) are not enlarged as in that genus, but arc small as they are in Lype and Tinodes; and the ventral apotome (c) is broad and triangular as in Lype and Tinodes, rather than the tiny equilateral triangle of Psychomyia. The mandibles of P nearctica (0, E) are naITOWer than in Lype and Tinodes, and the right mandible has a prominent mesal notch. The head of P nearctica (B) is longer than wide, rather than squarish as in Psychomyia. The prothoracic episternum has dorsal emarginations (A), lacking in the other genera. Membranous thoracic segments and the abdominal segments bear a prominent dark median dorsal band; anal papillae are evident (F). Length of larva up to 9 mm; the larva illustrated is probably not a final ins tar. Larvae of Paduniella construct silken tubes with sand and other materials adhering to them; several tubes are fastened to a single rock as in Psychomyia (Fig. 10.30). Tubes up to 22 mm in length and 2-3 mm in width were recorded by Mathis and Bowles (1994). RETREAT

• Populations of P nearctica are mainly confined to headwater streams of the Ozar Mountains, where larvae occur in areas of low velocity and large stable substrates (Mathis d Bowles 1994). Larval retreats were located in depressions on the upper surfaces of rocK Larvae fed mainly on diatoms, with a sizeable component of fine detritus in the summer. BIOLOGY

This single species is the sole North American representative of the subfamily Paduniellinae. Taxonomy of Paduniella adults in North America was reviewed by Armitage and Hamilton (1990); morphology of the female of P. nearctica was described by Bowles and Allen (1988).

REMAR KS

Paduniella nearctica (Arkansas, Washington Co., 10 July 1987, ROM) A, larva, lateral x approx. 17, detail of pleuron and trochantin; B, head, pro- and mesonotum, dorsal; c, maxillae, labium and ventral apotome, ventral; 0, mandibles, dorsal; E, mandibles, ventral; F, segment IX and anal prolegs, dorsal 178

Psychomyiidae: Paduniella 10.2

o A

1//

E

F

179

10.3 Genus Psychomyia are Holarctic and Oriental in distribution. Three species are known in North America: P. flavida Hagen throughout most of the continent to the edge of the tree line at Churchill, Manitoba (Lehmkuhl and Kerst 1979), and recorded also from Siberia (Schmid 1965); P. lumina (Ross) in the western United States; and P. nomada (Ross) in the east. The larva of P. flavida was described by Ross (1944), and larvae of P. flavida and P. nomada by Flint (1964a). We have associated material for these species, and larvae of a western species illustrated here from material we collected in Oregon, which is probably P. lumina. DIS T R IB U TI 0 NAN I) S PEe I E S Psychmnyia

Psychomyiid larvae in North America with teeth on the ventral, concave margin of the anal claw (A) belong to Psychomyia or Paduniella. In Psychomyia the submental sclerites are very large, each one much longer than wide, and the ventral apotome is reduced to a small equilateral triangle (c). In the series illustrated, probably P. lumina, the anterior margin of the frontoclypeal apotome (B) lacks the median notch characteristic of the other two species; larvae of all three Nearctic species can probably be separated on the basis of different development of this notch (cf. Flint 1964a, fig. 5). Length of larva up to 9 mm. MORPHOLOGY

The larvae illustrated constmct meandering tubes of silk several centimetres long covered with sand grains on rocks (D). In eastern species these tubes are little more than I cm in length. RETREAT

In North America, Psychomyia larvae are usually found in rivers and streams, although European species are also reported from the littoral zone of lakes (Lepneva 1964). Gut contents of P. flavida in a Pennsylvania woodland stream were found to be largel~algae with smaller proportions of detritus and animals (Coffman et a1. 1971). Guts (3) frOm the larval series illustrated all contained some vascular plant tissue, as well as fine organ~particles. P. flavida is probably facultatively parthenogenetic (Corbet 1966); females are often abundant in light traps 1 and males, though infrequently collected, are sometimes found in equal proportions. BIOLOGY

I !

~

,

Taxonomy and distribution of adults were summarized by Armitage and Hamilton (1990).

REM ARKS

)

,

Psychomyia (prob. lumina) (Oregon, Benton Co., 7 April 1964, ROM) , A, larva, lateral xIS, tarsi and anal, claw enlarged; B, head, pro- and mesonotum, dorsal; c, ventral apotome and mouthparts, ventral; 0, rock with sand-covered tubes, approx. xO.25, section of tube enlarged 180

j

1

Psychomyiidae: Psychomyia 10.3

A

maxillary lobe

submental sclerite ventral apotome

/

o

181

10.4 Genus Tinodes Species of Tinodes occur in most faunal regions. In North America north of Mexico twelve species are recognized, all in westcrn montane areas. Generic characters for Tinodes larvae were given by Ross (1959) and Flint (l964a). In the ROM collection we have larvae for three species and series of larvae from several other localities.

DISTRIBUTION AND SPECIES

In larvae of Tinodes each mandible usually has a prominent dorsal bump near the lateral margin distad of the base (D, E), but the bump is often larger on one mandible. The dorsolateral mandibular condyle basad of the bump mayor may not be prominent. The pair of lateral setae on each mandible is situated at about its mid-point; the left mandible bears only a single setal brush on the inner edge, and both mandibles are somewhat longer than wide. The submental sclerites are usually larger than in Lype, approximately half as long as wide. Some European species have small teeth on the concave edge of the anal claw, but North American larvae now known lack these teeth (A). Length of larva up to 15 mm.

MORPHOLOGY

Tinodes larvae construct flattened, silken tubes covered with sand, usually on rock surfaces (F); the tube has a thin silken floor. Tubes are variable in length, but often reach several centimetres.

RETREAT

Our larval collections were made in rather warm streams of desert country. Those assumed to be T. powelli Denning came from isolated pools of a desert stream of widely fluctuating flow in California (Deep Creek, P.L. Boyd Desert Research Center, Riverside Co., provided by S.L Frommer); adults were collected in June. Water temperatures in a series of these pools in Deep Creek ranged from 18 to 27.5°C (Frommer and Sublette 971). Larvae assumed to be T. provo Ross came from a spring-fed stream in Idaho (Deep reek, Oneida Co., provided by R.L. Newell) with a constant temperature of approximately ~C; adults were collected in January, but some other aquatic insects, normally bivoltine, had,multivoltine life cycles at this site (R.L. Newell, pers. comm.). Larvae feed mainly on detritus and algae. BIOLOG Y

Taxonomy of adults was reviewed by Denning (1956), and more recently by Armitage and Hamilton (1990).

REMARKS

Tinodes (prob. powelli) (California, Riverside Co., 13 June 1969, ROM) A, larva, lateral x12, claws of tarsus and anal proleg enlarged; B, head, pro- and mesonotum, dorsal; C, pleuron and trochantin with fore coxa, lateral; D, mandibles, dorsal; E, right mandible, lateral; F, section of retreat, dorsal approx. x4 182

I

Psychomyiidae: Tinodes 10.4 episternum

•• suture

pleural suture ,

- - trochantin

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/ F

183

11 Family Xiphocentronidae

From inception as a family of one genus (Ross 1949), the Xiphocentronidae have become through recent revision a family of seven genera with about one hundred species (Schmid 1982). As defined by Schmid, the family is widely distributed through Asia, Africa, South America, Central America and the Antilles, and North America. The genus Xiphocentron is represented in southwestern North America. Adults of a second genus of this family, Cnodocentron, have been recorded from Arizona (Moulton et a1. 1994); larvae are unknown in Cnodocentron. Larval diagnosis for the entire family cannot be given because four of the seven genera assigned to the Xiphocentronidae (Schmid 1982) are unknown as larvae. Larvae are known for Xiphocentron from the New World. Larvae of Abaria from Africa (Scott 1985) are morphologically congruent with Xiphocentron. The larva of Melanotrichia serica from Asia is also congruent with Xiphocentron (Barnard and Dudgeon 1984). However, in his revision of the Xiphocentronidae based on adult stages, Schmid (1982) found that few of the morphological characters of the type genus Xiphocentron were diagnostic for the family as newly defined. Until larvae of these remaining genera become known, and their morphology studied, I treat the larval diagnosis for Xiphocentronidae here in terms of the type genus Xiphocentron.

185

11.1 Genus Xiphocentron Species of Xiphocentron occur in Mexico, the Antilles, and Central and South America (Schmid 1982). One species, X. messapus Schmid, occurs in southern Texas; the larva and pupa were described by Edwards (1961, as X. mexico Ross). DISTRIB UTION AN D SPECIES

Larvae of Xiphocentron resemble those of the Psychomyiidae in general structure (A), but the prothoracic trochantin is not broad and hatchet-shaped as in that family. The partly membranous trochantin of Xiphocentron is much smaller, although it is separated from the propleuron by a well-marked suture (E). The larva of Xiphocentron is further distinguished by a lobate process extending anterodorsad from the mesopleuron (A, B); the base of this process arises from within a linear invaginated pocket (D). The tibiae and tarsi of all legs are fused together as a single segment (A, D); the posterolateral corners of the pronotum are extended ventrally as a thin sclerotized band. The ventral apotome of the head is broadly triangular as in psychomyiids such as Tinodes, but submental sclerites are lacking (c). The labium is elongate and labial palpi are lacking (c), as in Psychomyiidae, and the maxillary lobes arc prominent. Anal papillae are present. Length of larva up to 8 mm.

MORPIIOI"OGY

RETREAT According to Edwards (1961), larvae of Xiplwcentron messapus build tubes

of fine sand grains on rocks below the water surface, and the tubes frequently extend several centimetres above the surface on wet substrates; tubes up to 5 cm long and 2.5 mm wide were recorded. I have collected Xiplzocentron larvae in sand tubes up to 10 cm in length from rocks in cloud-forest streams in Costa Rica; the tubes are similar to those constructed by larvae of the psychomyiid genus Tinodes. At the ends of tubes on the undersides of logs overhanging streams, larvae of a Colombian species constructed pendant ovoid vesicles of silk in which they pupated above the water (Sturm 1960). ~

B I 0 LOG Y 'batvae of X. messapus were found in the outflow of a small spring (Edwards

1961), and the A~lti1les species live in small streams (Flint I 964b). The lobate process of the mesopleuron is unusual, if not unique, in trichopteran larvae; its membranous surface and oddly invaginated base suggest some sensory function. Since the mandibular structure and tube-making behaviour of Xiplzocelltron larvae are similar to the Psychomyiidae, it is reasonable to infer that these larvae also graze algae and organic particles. Taxonomy based on adult morphology was summarized by Armitage and Hamilton (1990). Larvae illustrated were provided by O.S. Flint.

REMARKS

Xiphocentron messapus (Texas, Hays Co., I July 1960, USNM) A, larva, lateral x24, anal claw enlarged; B, head, pro- and mesonotum, dorsal; c, head, ventral; D, prothorax and mesopleuron, right side, lateral; E, fore trochantin, right side, ventral 186

Xiphocentronidae: Xiphocentron 11.1

A

B

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187

Suborder INTEGRIPALPIA: Portable-case makers Larvae are mostly eruciform with an hypognathous head; the anal prolegs are short and the anal claws are small. Portable cases constructed in all instars enable larvae to move to new food resources. Pupation in most families occurs within the larval case, after the case has been fixed to a substrate and the ends closed against predators. Small openings in the ends of the case permit water to flow directly over the developing pupa for respiration; a flow of water through the case is regulated by the ventilating undulations of the insect's abdomen. The world fauna of the Integripalpia consists of approximately 30 families, and several are endemic to the northern or southern hemispheres. In North America 15 families are represented. 12 13 14 15 16

Apataniidae Beraeidae Brachycentridae Calamoceratidae Goeridae

17 18 19 20 21

Helicopsychidae Lepidostomatidae Leptoceridae Limnephilidae Molannidae

22 23 24 25 26

Odontoceridae Phryganeidae Rossianidae Sericostomatidae Uenoidae

The superfamilies Phryganeoidea (p. 10) and Limnephiloidea (p. 11) were defined by Gall and Wiggins (in press); evidence for the Leptoceroidea (p. 13) and Sericostomatoidea (p. 13) was reviewed by Frania and Wiggins (1995).

189

12 Family Apataniidae

The family Apataniidae (Gall and Wiggins, in press) brings together the subfamily Apataniinae, formerly of the Limnephilidae, with four of the genera placed previously as Limnephilidae incertae sedis (Wiggins 1973c). Members of the Apataniidae are widespread in the Holarctic and Oriental faunal regions; five genera are represented in North America. The Apataniidae represent the coincidence of several uncommon trends in larval characters: wedge-like shape of the ventral apotome; mandibles with scraper blades for grazing; pronotum inflated; and metanotal sal with many setae on the integument. Not all of these characters occur in each genus, and the genera differ in some other characters. In all genera, the antennae are located between the eye and the anterior margin of the head capsule. Metanotal sal sclerites are lacking in two genera. Abdominal gills are single or lack• mg. Larvae of t' amily are primarily residents of cool running waters, but under conditions of the far north 0 t high elevation, Apatania larvae live in cold lakes. Moselyana larvae appear to be confined to the organic muck of spring seepage areas. All Nearctic species construct cases of small rock fragments, although larvae of Manophylax add bits of plant detritus, apparently as surface camouflage rather than as integral parts of the case structure.

Key to Genera*

1

Metanotal sal sclerites discrete, about the same size as the sa2 sclerites (Fig. 12.38) 2 Metanotal sa 1 sclerites lacking, but the setae present and continuous across the dorsum as a line (Fig. 12.28) or a broad patch (Fig. 12.58) 4

2

(l) Basal seta of tarsal claws short, extending far short of tip of claw (Fig. 12.4A);

*See qualifications under Use of Keys, p. 7. 190

,

12 Family Apataniidae mandibles with separate tooth-like points (Fig. 12.4D); many metanotal setae 12.4 Moselyana not on primary sclerites (Fig. 12.4B). Western Basal seta of tarsal claws long, extending to or almost to tip of claw (Fig. 12.1A); mandibles with apical edge entire and not subdivided into tooth-like points (Fig. 12.1D); most metanotal setae confined to primary sclerites (Fig. 12.3B) 3 3

(2) Venter of abdominal segment I with an anteromedian sclerite (Fig. 12.3E), with or without a central unsclerotized area; head unmodified and uniformly convex (Fig. 12.3B). Eastern and western 12.3 Manophylax

Venter of abdominal segment I lacking an anteromedian sclerite; dorsum of head flattened, frequently with prominent carina (Fig. 12.1A, B). Western

12.1 Allomyia 4

(1) Metanotal sa 1 setae arranged more or less linearly across mid-dorsal line,

mesonotum with two large, undivided plates (Fig. 12.2B). Widespread

12.2 Apatania Metanotal sal setae abundant in broad patch across mid-dorsal line, mesonotum with each plate subdivided longitudinally into two sclerites (Fig. 12.SB). Western 12.5 Pedomoecus

191

12.1 Genus Allomyia This genus, formerly Jmania, comprises 12 specics occUlTing in mountainous areas of western North America from Alaska to Colorado and Nevada; other species occur in eastern Russia and Japan. Larvae referred to Limnephilid Genus A by Ross (1959) and Flint (1960) are Allo11lyia. We have identified larvae for four species (Wiggins 1973e) and collected series belonging to this genus from many western localities. The larva of a Siberian species, A. sajanensis Levanidova, has been described (Levanidova 1967). DISTRIBUTION AND SPECIES

The head in larvae of Allomyia is flattened dorsally, the dorsum frequently concave and bounded by a sharp, semicircular carina (B); posterodorsal horns on the head (A, B) are known only in A. scotti (Wiggins). The head and pronotum have a pebbled texture. Other characters of the head include scraper mandibles with apical edges entire and not subdivided into teeth (D), a T-shaped ventral apotome (F) in which the lateral margins are straight rather than convex as in the other genera, and a labrum with a membranous anterior margin (E). The pronotum is strongly convex, the mesonotal plates are shorter than in most other genera, and most metanotal setae are confined to the primary sclerites; the basal seta of the tarsal claws extends almost to the tip of the claw (A, B). Abdominal gills may be present but usually are lacking. Length of larva up to 11.5 mm. MORPHOLOGY

Larvae build a tapered, cylindrical case of small but coarse rock fragments. The case of A. scotti (c) is unique in having the basal quarter sharply constricted from the remainder. In cases of A. cidoipes (Schmid) there is a ridge of small stones along each side. Length of case up to 13 mm. CAS E

Lalvae live in small, cold mountain streams, often at high elevations, and frequently occur on vertical rock faces in a thin layer of flowing water; they also occur on rocks in turb!Ilent streams. Gut contents of larvae (3) we examined were largely fine organic and miI1cf

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229

16.2 Genus Goeracea Goeracea is a Nearctic genus recorded from montane areas of western North America: British Columbia, California, Idaho, Montana, and Oregon. Two species are known, G. genota (Ross) and G. oregona Denning. We have associated larvae for both species, and data for larvae and adults were pre. sented elsewhere (Wiggins 1973b).

DISTRIBUTION AND SPECIES

MORPHOLQG Y Larvae of Goeracea are unusual in appearance and unlikely to be con-

fused with any other genus. The pronotum is flat and rounded in dorsal outline, and heavily thickened laterally; the mesepisternum is laterally compressed and long (A). Each metanotal sal consists of one or two setae without a sclerite or with a very small selerite. Gills arc single and confined to segments III and IV or to III alone. Ventral chloride epithelia are present; and the two stout setae comprising the basal tuft of the anal pro\cg arise from a small sclerite, the dorsal plate (G). Typically for the Goeridae, mandibles have scraping edges rather than distinct teeth (D), the basal seta of each tarsal claw extends nearly to the tip of the claw (A), and the anterior border of the labIUm is membranous (F). Length of larva up to 6.6 mm. CASE The larval case (c) is of rock fragments, curved and tapered, with a row of larger

pebbles along each side; frequently a mid-dorsal ridge of small stones is also attached to the central tube. The silken membrane reducing the posterior opening of the case has an eccentric, relatively small opening. When the larva is withdrawn into the case, the anterior opening is closed entirely by the pronotum and the mesothoraeic sclerites, and the head is folded completely beneath the pronotum. Length of larval case up to 8 mm. Larvae of Goeracea inhabit small, cold streams in mountainous areas where they arc usually found on rocks. Gut contents of larvae (6) we examined were mainly [inc organic and inorganic particles with a small proportion of vascular plant pieces. BIOLOGY

Goeracea geliota (Oregon, Benton Co., 13 April 1964, ROM) A, larva, lateral x26, tarsal claw enlarged; B, head and thorax, dorsal; c, case, dorsolateral x 14; D, mandible, dorsal; E, head, ventral; F, labrum, dorsal; G, segment IX and anal prolegs, dorsal 230

16.3 Genus Goerita DISTR IB UTION AND SPECIES The genus is confined to North America and is known

only from the eastern part of the continent; there are two species, G. semata Ross and G. betteni Ross. Larvae identified circumstantially as G. sel1lata were described by Flint (1960) and by Wiggins (1973b); larvae of G. betteni were identified by Wiggins (1973b), and taxonomic data for adults of both species were also provided. MORPHOLOGY These arc the only North American goerid larvae known with no

abdominal gills. The prominent median hump on the pronotum is distinctive, and the anterolateral processes and lateral thickening arc similar to Goera (A, B). The antennae arc set in dcpressions (B) as in several other goerid genera. Sclerotized parts are reddish brown, the head and thoracic nota having a pebbled surface. Ventral chloride epithelia arc present on segments lV-VI; the two stout setae comprising the basal tuft of the anal proleg arise from the dorsal plate (D) as in several other genera of the Goeridae; forked lamellae are reduced in number, and a lateral fringe is lacking. Length of larva up to 6 mm. CASE Larvae construct a smooth-sided case of sand grains; those of G. betteni incorpo-

rate larger pieces in the lateral walls of the case (c), behaviour suggestive of Goeracea where a row of larger stones is added to each side of the case. The posterior opening is restricted with silk to a small hole dorsad of centre. Length of larval case up to 6.5 mm. BIOLOGY Larvae of both species occur on rocks in small, cold spring runs in mountain-

ous areas; colonies are exceedingly local in distribution. Gut contents of larvae (3) we examined were mainly fine organic and mineral particles, consistent with the behaviour of grazing on rock surfaces. The life history and production of G. semata were studied by HUlyn and Wallace (1985); the life cycle extended over two years, and two distinct cohorts were present at anyone time. Diatoms were the principal food in spring, but amorphous detritus constituted a larger proportion of the gut content at other times of the year.

Goerita betteni (Tennessee, Franklin Co., 14-15 May 1970, ROM 7(0337) A, larva, lateral x22; B, head and thorax, dorsal; C, case, ventrolateral x16; D, segment IX and anal prolegs, dorsal 232

16.4 Genus Lepania Lepania is an unusual Nearetie genus with a single species, L. cascada Ross, known from Oregon and Washington. Morphology of all stages was described and relationships of the genus assessed elsewhere (Wiggins 1973b). DISTRIBUTION AND SPECIES

Subdivided plates of the mesonotum and an elongate mesepisternum (B), along with thickened lateral edges on the stout pronotum, establish the larva as a member of the Goeridae; within that group the larva of Lepania is most readily distinguished by the dorsally depressed mesepisternum and the well-developed metanotal sa I sclerites. Atypically, the larva of L. cascada has mandibles with separate teeth (D) and short basal setae on the tarsal claws (A). The head bears many secondary setae dorsally (B), and the antennae are set in lateral concavities (H); the ventral apotome has concave lateral margins (F). Abdominal gills are reduced to two pairs of single filaments on segment III (A), forked lamellae are reduced, and a lateral fringe is lacking; a small dorsal plate lies beside the basal tuft of the anal proleg (G), and the anal claw lacks an accessory hook. Length of larva up to 5.5 mm.

MORPHOLOGY

CASE Larvae of L. cascada construct a case of small rock pieces, curved and strongly

tapered (c); rock pieces on the venter are smaller than those placed dorsally and laterally. Length of larval case up to 5.5 mm. BIOLOGY This exceedingly local species occurs in spring seepage sites in mountainous

country. From our field observations on Marys Peak, Oregon, it is evident that larvae are restricted to the water-saturated organic muek at the head of springs. Gut contents of larvae (3) we examined were mainly pieces of vascular plants with some algae. Adults fly in June, but the presence of early-instar larvae at the same time suggests that more than one year is required for completion of the life cycle, as has been shown for Goerita. Phylogenetic analysis of the Goeridae (Gall and Wiggins, in prep.) reveals that the basal lineage still extant in this family is probably Archithremma of the Russian Far East; Lepania was inferred to be the next oldest lineage .

REMARKS

•

Lepania cascada (Oregon, Benton Co., 14-15 June 1968, ROM) A, larva, lateral x23, tarsal claw enlarged; B, head and thorax, dorsal, detail of mesonotum; C, case, lateral x 18; D, mandible, ventral; E, labrum, dorsal; F, head, ventral; G, segments VIlI, IX and anal prolegs, dorsal; H, right side of head, dorsal 234

Goeridae: Lepania 16.4 A

D

F

,

,

, mesepisternum

G sa2

235

•

•

17 Family Helicopsychidae

So abundant and widespread are these caddisflies, it is easy to forget that the larvae are among the most remarkable of all insects. Their helical cases of closely fitted rock fragments are an outstanding example of the elegance and precision of insect behaviour. The family comprises four genera, with representatives widely distributed over most faunal regions (Schmid 1993); a single genus, Helicopsyche, occurs in North America. Aspects of the morphology and biology of a European species were outlined by Boto§aneanu (1956). Larval cases of most species resemble tightly coiled snail shells, although a Cuban species has an open-coiled case (Boto§aneanu and Sykora 1973) suggestive of Baikalia, an unusual endemic snail genus of Lak(! Baikal. The case of the most common North American species, Helicopsyc/ze borealis, was originally described as a snail having 'the remarkable property of strengthening its whirls by agglutinations of particles of sand, by which it is entirely covered' (Lea 1834). The coiled case of the Helicopsychidae must have been derived from the more usual tube-case-making behaviour; and perhaps there is some advantage for the larvae in consolidating the mass of the case. Helical cases, for example, seem well suited to interstitial habitats; larvae of H. borealis were found to depths of 30 cm below a stream bed (Williams and Hynes 1974), and their cases proved more resistant to crushing than those of other families tested (Williams et al. 1983). Within their cases, larvae lie on one side, the abdomen coiled more dorsoventrally than laterally. An opening on the spire of cases of H. borealis corresponds to the posterior opening of tube-cases, facilitating water circulation through the case. Helical cases are not wholly confined to the Helicopsychidae, but are also constructed by larvae in the South African leptocerid genus Leptecho (Scott 1961).

237

17.1 Genus Helicopsyche DISTRIBUTION AND SPECIES This is a genus of about 100 species represented in

most faunal regions (Schmid 1993). In North America a dozen or so species are known from Mexico, but only four north of the Rio Grande: H. piroa Ross in Texas; H. mexicana Banks in Arizona and Texas; H. limnella Ross in Arkansas and Oklahoma; and H. borealis (Hagen) widespread and common over much of the continent. The northern limit of H. borealis is uncertain, but we have records from Saskatchewan to 55°N lat. Of these four species, only the larva of H. borealis has been described, by Vorhies (1909) and Elkins (1936) among others. We have many series of larvae from North America. MO RP II 0 L OG Y Structural features are evident in the illustration. The fore trochantin is

unusually long (A), and the comb-like structure of the anal claw (D) is unique among North American larvae. Forked lamellae (E) arc confined to segment VIII. CASE The snail-like cases made of sand grains (c, F) provide an unmistakable diagnosis

for larvae of Helicopsyche. The dorsal lip of the anterior opening is extended as a hood, covering the larva as it grazes on rock surfaces. Diameter of case up to 7 mm. BIO LOG Y Larvae of Helicopsyc/ze spp. are normally associated with running water, but

those of H. borealis arc also common in the littoral zone of lakes. Vorhies (1909) found larvae to depths of 8-10 feet in Wisconsin lakes. Larvae of H. borealis have an exceptionally broad temperature tolerance; we collected larvae of this species in thermal streams of Yellowstone National Park, Wyoming, where temperatures ranged up to 34°C and no other caddis larvae were found. In other streams with thermal afi1uents in California and Montana, Helicopsyc/ze larvae were always among the few Trichoptera present. Experimental analysis of thermal tolerance and feeding behaviour was carried out by Resh et al. (1984). Food of H. borealis larvae, analysed by Coffman et a!. (1971) and Mecom (1972a), consisted of algal, detrital, and animal materials. From some studies there appears to be a continual emergence of H. borealis adults from spring through early autumn (Ross 1944), followed by a long egg-diapause of 5-6 months (Williams and Hynes 1974); but no evidence of diapause or extended emergence was found in a study of this species in California (Resh et a!. 1984). The biology of H. borealis was studied in Ontario by Williams et al. (1983); larvae fed on diatoms and detritus, the proportions changing with seasonal availability.

•

Helicopsyche borealis (Ohio, Ashland Co., Aug. 1968, ROM) A, larva, lateral x21 ; B, head and thorax, dorsal; c, case, lateral x 16; D, anal claw; E, forked lamellae on segment VlIl, x580; F, case, dorsal 238

Helicopsychidae: Heiicopsyche 17.1

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239

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1

18 Family Lepidostomatidae .

The Lepidostomatidae are widely distributed over much of the world, primarily in the Holarctic, Oriental, and Afrotropical regions; a few species also occur in northern parts of the Neotropical region of Mexico through Panama, and of the Australian region in New Guinea. A synopsis of the North American Lepidostomatidae has been provided by Weaver (1988) in which about 80 species are recognized. Genera have been unstable through much of the taxonomic history of the Lepidostomatidae. Generic characters based on the richly varied secondary sexual structures of the males led to the proposal of some 15 names in North America; these were reduced to two genera, Lepidostoma and Theliopsyc/ze, by Ross (1944, 1946). Within the genus Lepidostoma, four subgenera were proposed by Weaver (1988) for the North American species: L. (Lepidostol1la), L. (Mormomyia), L. (Neodinarthrum), and L. (Nosopus). Proposals for generic classification of the North American Lepidostomatidae have been made almost entirely on the basis of characters of the adults; little taxonomic information has been available for larvae. A key to larvae of species groups and some species was provided by Weaver (1988), based mainly on case structure and geographic distribution with some morphological information; the subgeneric groups proposed for Lepidostol1la lack larval diagnoses. In an attempt to augment the proposed classification with larval diagnoses, a comparative study was made of associated larvae of 12 North American species representing the four subgenera of Lepidostoma sens. lat. (Kerr and Wiggins 1993); detailed comparison of morphology including surface sculpture and chaetotaxy was included. From structural .characters, several of the larvae could be distinguished at the species level, but diagnostic larval characters were congruent only in two of the subgenera. Larvae of two species of L. (Neodillarthrum) were distinguished by pronotal surface sculpture; and two species of L. (Lepidostol1la) shared sparse secondary setation on the mesonotum. These provisionallarval characters for two of the subgenera are not proposed as taxonomic diagnoses because larvae of the large majority of species of Lepidostoma sens. lat. are still unknown. There is a tendency in the classification of insects for subgenera to become genera. However, most genera of Trichoptera now recognized in North America can be identified 241

18 Family Lepidostomatidae in the larval stage. This is an important functional principle of generic taxonomy; and it can be hoped that systematists proposing changes in the generic classification of Trichoptera will ensure that the character base includes concordant larval diagnoses (Kerr and Wiggins 1993: 119). Larvae of the Lepidostomatidae are generally similar to those of the Limnephilidae, but are distinguished by the position of the antennae close to the eyes, by the absence of a median dorsal hump on abdominal segment I, and by the absence of chloride epithelia enclosed by sclerotized oval rings on the abdominal segments. North American lepidostomatid larvae that we have examined possess a dense patch of pectinate spines on the distal end of the hind coxa (Fig. 18.1A). The mandibles have separate teeth, and the prosternal hom is well developed. Abdominal gills are single and arranged in dorsal and ventral rows only, or are lacking; the lateral fringe is sparse and often absent, and forked lamellae occur on several segments. Segment VIII bears a broad lobe at each side. Anal papillae are usually present. The majority of lepidostomatid larvae in North America are generally concordant with the one illustrated here as Lepidostoma. But in some of our collections from the west, the density of secondary setation on meso- and metanota is much greater than in typical Lepidostoma, or the head is flattened much as in Theliopsyche, or bulbous as in the limnephilid genus Ecclisocosmoecus; or the pronotum is modified to resemble that in Goera. Different larval cases are associated with some of these distinctive morphological characters. The typical larval case associated with this family is four-sided, and constructed of quadrate pieces of bark and leaves (Fig. 18.1e); in four-sided cases of the Lepidostomatidae the component pieces are squarish, distinguishing them from four-sided cases of the Brachycentridae in which the pieces are slender. But the North American lepidostomatid fauna also includes larvae that build several other types of cases - of bark and leaf pieces arranged irregularly, of leaf pieces arranged spirally (Fig. 18.10), of pieces of plant stems arranged transversely (Fig. 18.1H), and of sand grains too (Fig. 18.1F). These examples indicate that a good deal of larval diversity has yet to be incorporated into the data base for Lepidostomatidae in North America. For the present, all of these larval types, apart from Theliopsyche, are assigned provisionally to Lepidostoma; larvae of Theliopsyche have few distinctive characters. It can be noted that adults of the eastern Lepidostoma togatum (Hagen) were assigned to the genus Goerodes by Corbet et al. (1966) and by Nimmo (1966); associated larval material of that species in the ROM collection indicates little discordance from typical Lepidostoma. Two subfamilies have been proposed for the Lepidostomatidae (Weaver 1993): Lepidostomatinae and Theliopsychinae. The two are broadly similar in global distribution, but the Theliopsychinae, now with only four extant genera and 4 per cent of the species, were a major part of the Lepidost.omatidae in Baltic amber deposits of Oligocene age some 40 million years ago. Most larvae of this family occur in small, cold streams; in larger rivers they tend to frequent sections of slower current, and they are also found in the littoral zone of lakes. Lepidostomatid larvae are detritivorous, and are usually associated with accumulations of leaves and other plant materials.

242

.,

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Key to Genera* 1

Head usually unmodified and without carina (Fig. IS.1 8), but carina present in a few western species; cases of plant pieces usually 4-sided (Fig. IS.1 c), but pieces also arranged irregularly, transversely (Fig. IS.1 H), or spirally (Fig. lS.1 G); cases also of sand grains (Fig. IS. IF). Widespread 18.1 Lepidostoma Head with dorsal peripheral carina (Fig. lS.28); cases of sand grains. Eastern 18.2 Theliopsyche

*See qualifications under Use of Keys, p. 7. 243

1

I 18.1 Genus Lepidostoma

, i

DISTRIBUTION AND SPECIES Lepidostoma is primarily a Holarctic and Oriental

genns to which about 75 North American species have been assigned. The group is widespread over much of the continent, although most of the species are western. Larvae have been described for few species: L. griseum (Banks) by Sibley (1926); L. liba Ross by Ross (1944); L. bryanti (Banks) (as L. wiscollsinensis Vorhies) by Vorhies (1909). We have associated larval material for about 25 other species (e.g. Kerr and Wiggins 1993).

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M 0 R P II 0 LOG Y The larval diagnosis for Lepidostoma used in the generic key sub-

sumes the aberrant forms referred to previously in the introduction to this family. Most North American larvae are, however, generally concordant with the one illustrated here (A-E). Length of larva up to 12.5 mm. CASE Cases of late-instar larvae in most species of Lepidostol11a arc usually four-sided

and constructed of quadrate pieces of bark or leaf (c); observations indicate that in at least some of these species early-instar cases are of sand grains and cylindrical, with the foursided case of bark and leaves built on the anterior end during later instal'S (Vorhies 1909; Hansell 1972). Final instars in some other species assigned to Lepidostoma have cases of plant materials placed spirally or transversely (0, H), or sand grains (F). Length of larval case up to 15 mm. BIOLOGY

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Lepidostoma larvae most often occur in cool springs and streams, usually in

areas of little current, but they arc also found in lakes and in temporary stn.;ams (Denning 1958a; Mackay 1969). Food studies of Lepidostol11a larvae show that detritus comprises the major part of the materials ingested (Chapman and Demory 1963; Winterbourn 1971 a; Anderson and Grafius 1975), and larvae arc usually found in association with dead plant material; larvae arc also attracted to dead fish (Brusven and Scoggan 1969). Life- history data published by Anderson (l967b) and Mackay (1969) show a single generation per year [or five species studied, and indicate as well thal there is temporal and spatial separation among larvae of different species living in the same habitat.

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Lepidostoma 5pp. A-E (Ontario, Hastings Co., 15 Oct. 1968, ROM) A, larva, lateral x 17, apex of hind coxa enlarged; B, head and thorax, dorsal; c, case x 10; D, eye and antenna, lateral; E, head, ventral

(Arizona, Cochise Co., 23 June 1966, ROM), case x5 a (Oregon, Clatsop Co., 14 July 1963, ROM), case x4 H (Oregon, Douglas Co., 4 July 1961, ROM), case x5 F

244

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20.29 Genus Phanocelia This is a monotypic genus confined to northern North America. A single species, P. canadensis (Banks), has been recorded from the Northwest Territories, Alberta, Manitoba, Quebec, Nova Scotia, New Brunswick, and New Hampshire; sparse records for P. canadensis indicate that populations are highly localized. Information on the immature stages and biology was provided by Fairchild and Wiggins (1989). DISTR IB UTION A ND SPECIES

Among larvae of North American Limnephilidae with single-filament gills (A), Phanocelia is distinguished by short, wide mesonotal sclerites (B), and by sparse setation and lightly sclerotized oblique bands on abdominal segment I (A, D). Mesonotal setal areas 1, 2, and 3 are discrete, each represented by several setae (B); metanotal setae are confined to the three primary sclerites. Abdominal segment I bears approximately four setae at each side of the dorsal hump and also dorsad of each lateral hump, 1-2 setae ventrad of each lateral hump (A), and 2-3 pairs of median ventral setae (D). Abdominal gills are single (A), chloride epithelia occur ventrally on abdominal segments IV through VII (A), and forked lamellae are lacking; a linear band of fine setae extends across the posterior margin of segment VIII (E). The claw of the anal proleg bears a single accessory hook; typically for the Chilostigmini, lateral sclerites of the anal prolegs bear stout, clear setae among longer black setae. In well-sclerotized larvae of P. canadensis, a pair of indistinct sclerous points may be visible at the posterodorsal margin of each lateral hump (A); these points could lead to confusion with Desmona, but they are not ring-like, and the short mesonotal sc1erites are diagnostic for Phanocelia. Length of larva up to 12 mm. MORPHOLOG Y

Larval cases of Phanocelia now known are distinctive in construction, with short pieces of sphagnum moss arranged transversely. Length of larval case up to 10 mm. CASE

Larvae of P. canadensis are known yet from only a single site - a typical sphagnum bog pool in New Brunswick (Fairchild and Wiggins 1989); there they occurred in the floating fringe of moss around the open pool in water of pH 4.1. Whether they are restricted to sphagnum bog pools remains to be confirmed. Gut contents indicate that larvae feed on Sphagnum, insect larvae, and crustaceans. Larvae are univoltine, pupating and emerging in late summer. B I 0 LOG Y

Diagnostic characters for adults of P. canadensis have been summarized and illustrated by Nimmo (l971) and by Schmid (1980). A metamorphotype of this species from 1100 years B .P. has been documented from southern Ontario (Wiggins 1991). REM ARKS

Phanocelia canadensis (New Brunswick, York Co., June 1985, ROM) A, larva, lateral x 11, fore leg and abdominal segment I enlarged; E, head and thorax, dorsal; C, case, lateral x8; D, abdominal segment I, ventral; E, segments VIII and IX, dorsal (From Canadian Entomologist) 334

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20.30 Genus Philarctus f DISTRIB UTION AN)) SPECIES This is a northern genus of the Holarctic region, with

only one North American species, P. quaeris (Milnc), which is known from Manitoba to Yukon and south to Colorado. Lalvae associated in Manitoba have been described elsewhere (Wiggins 1963). MORPHOLOGY Three light-coloured areas on the narrowed portion of the fronto-

clypcus occur in Asynarchus, ClistolVllia, and Limnephilus as well as in Philarctus. A provisional diagnostic character for Philarctus is found on the mesothoracic femur (D.H. Smith, pers. comm.); the proximal of two major ventral setae is located about midway between the proximal end of the femur and the more distal seta (A). The accessory hook on the anal claw is single and lacks basal spines. Because of the close morphological similarity between larvae in Philarctus and Lil1lllephilus, and of the large number of Li/1lnephilus spp. for which larvae are not known, separation between the two genera is equivocal at this stage in our knowledge. Length of larva up to 18.5 mm.