Glenn B. Wiggins - Caddisflies: The Underwater Architects

CADDISFLIES

The Underwater Architects

Caddisflies constitute the insect order Trichoptera in which some 10,000 species are now known in the world, including about 1400 in Canada and the United States. This book is a comprehensive reference about caddisflies for freshwater biologists, entomologists, and students in those fields of study. The underlying theme of the book is that the effective roles of caddisflies in the flow of energy and nutrients supporting freshwater ecosystems is due largely to extraordinary diversification in larval architecture. The book is concerned with behavioural ecology, evolutionary history, biogeography, and biological diversity of caddisflies.

In Part I several fundamental concepts of aquatic ecology are outlined, illuminating ways in which caddisflies help to make fresh waters work. Fossil evidence shows that caddisflies originated in the Triassic period some 200250 million years ago; the evolutionary sequence of photosynthesizing food resources from bacteria and algae through primitive plants to gymnosperms and angiosperms emerges as a significant factor in the diversification of caddisflies. Aspects of life cycles are examined, with evidence showing that the evolving architecture for pupation has been crucial in the radiation of caddisflies. Information from fossils and plate tectonics is analysed in a section on biogeography. Interactions between caddisflies and people are discussed in an Epilogue.

In Part II essential features of morphology, biology, and distribution are described for the 26 North American families of caddisflies; illustrated diagnostic keys are provided for larvae, pupae, and adults. Families that do not occur in North America are briefly summarized, and a revised classification for the 45 world families of Trichoptera is included.

In Part III supplementary comments enlarge on the sources of information and broaden the evolutionary context.

This book is also a resource for fly-fishers and naturalists interested in freshwater communities because it brings together information on caddisflies from widely scattered sources. Explanatory passages and illustrations have been added to make the book more widely informative.

GLENN WIGGINS is Curator Emeritus (Entomology) in the Royal Ontario Museum, and Professor Emeritus in the Department of Zoology, University of Toronto.

Frontispiece. Caddisfly larva in the case-making family Limnephilidae (Photograph by W.A. Crich; Royal Ontario Museum)

The Underwater Architects

Glenn B. Wiggins

University of Toronto Press Incorporated 2004

Toronto Buffalo London

Printed in Canada

ISBN 0-8020-3714-3 (cloth)

Printed on acid-free paper

National Library of Canada Cataloguing in Publication

Wiggins, Glenn B.

Caddisflies : the underwater architects / Glenn B. Wiggins.

Includes bibliographical references and index.

ISBN 0-8020-3714-3

1. Caddisflies. 2. Caddisflies North America. I. Title.

QL516.W53 2004 595.745 C2003-907152-9

Published in association with NRC Research Press in their monograph series.

NRC Monograph Editorial Board

Editor: P.B. Cavers

Board: W.G.E. Caldwell, K.G. Davey, S. Gubins, B.K. Hall, P. Jefferson, W.H. Lewis, A. May, N.R. Morgenstern, B.P. Dancik,

and the Royal Ontario Museum

A ROM PUBLICATION IN SCIENCE

The Royal Ontario Museum gratefully acknowledges the Louise Hawley Stone Charitable Trust within the ROM Foundation for its generous support of this publication.

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

University of Toronto Press acknowledges the financial support for its publishing activities of the Government of Canada through the Book Publishing Industry Development Program (BPIDP).

For Carol,
Greg, Linda, and Steven

I have watched what lives in water for most of my life. As a museum curator in entomology, I devoted part of my time to studying caddisflies a small order of insects in which the immature stages live in fresh waters of all kinds. To see caddis larvae at eye level, I have crawled around in streams, pored over the downsides of rocks, and waded in marshes and ponds; and I have passed countless nocturnal vigils waiting for adult caddisflies to find my illuminated sheet. All this was directed to studies in systematics the sector of science associated with museums and their research collections which explores and documents biological diversity and provides systems of classification and identification for living things. Systematics also undertakes to reconstruct the evolutionary history of living things, for, as Theodosius Dobzhansky has observed, nothing in biology makes sense except in the light of evolution.

This book stems from my goal to provide a comprehensive reference about caddisflies. Although I have written in the past on several of the topics included here, the book has allowed me to revisit them with the advantage of hindsight and to fit them into the context of geological time. Ecology shows that everything is connected, but palaeontology reveals that in the past things must have been connected in different ways. I have tried here to place caddisflies in the evolutionary context of an unfolding biosphere exploration in time as well as space. Taxonomy is necessarily an integral part of a comprehensive reference on caddisflies, and the book provides illustrated diagnostic keys with biological outlines for the North American families. A revised classification for world families is included.

On a global scale, caddisflies are a small part of biodiversity; even so, they are important animals in freshwater ecosystems, and understanding how fresh waters work ecologically requires knowledge of the aquatic insects, such as caddisflies, that live there. The underlying theme of this book is that the effective roles of caddisflies in the flow of energy and nutrients through freshwater systems is largely a result of extraordinary diversification in larval architecture. Construction behaviour of the larvae is interpreted as a pathway of natural selection in establishing new ecological niches for caddisflies. The book is concerned with behavioural ecology, evolutionary history, biogeography, and biological diversity of caddisflies. Primarily it is a reference for freshwater biologists and entomologists and for students in these fields of study. The book is intended as a bridge between entomology, where the extensive literature on aquatic insect ecology is largely unappreciated, and freshwater biology, which seldom relates to the evolutionary and biogeographic history of aquatic insects.

A comprehensive work such as this is a synthesis based on what is known, but it can also point up new directions to what is not known. Throughout the book, I have raised questions and drawn inferences that could lead to future insights. Some of these inferences will turn out to be wrong, but pursuit of better explanations will advance our understanding of Trichoptera. In a way, my sequencing is backwards. This book can be seen as a broad introduction to my earlier work on larvae of the North American caddisfly genera (1977, 1996a). Taken together, the two constitute part of the general reference sources for Trichoptera.