Caddisflies, the Underwater Architects

Glenn B. Wiggins
University of Toronto Press
2005; 292 pp.
Price: $125, hardcover
ICBN: 0-8020-3714-3

Caddisflies, or Trichoptera, are usually considered among the “minor orders” in general entomology textbooks or popular publications on insects. In the printed edition of Zoological Record, they are included in the volume “Other Orders.” The same is seen in the many pie charts meant to visually display the distribution of known diversity among the insect orders; in these representations, caddisflies are afforded only a tiny slice. As such, when compared with the overwhelming diversity seen in certain subgroups of Coleoptera, Diptera, Lepidoptera, and Hymenoptera, the diversity and importance of Trichoptera are often overlooked or underappreciated. Adding to their status are the secretive, crepuscular habits of the small, somber adults and the aquatic habitat of the immature stages—characteristics that render their collection and observation unfavorable to all but the specialists.

   With almost 12,000 described species, Trichoptera ranks as the seventh largest order of insects (closely behind the Orthoptera) and is larger than many other more “popular” groups of arthropods and even vertebrates. The importance of caddisflies in the trophic dynamics and energy flow of freshwater ecosystems is a direct reflection of their biological diversity and abundance. Furthermore, biological indices and other metrics incorporating relative abundance and diversity of larval Trichoptera have long been used by state and federal agencies to assess and monitor water quality. The use of silk by larvae to construct intricate portable cases as protection from predators, to weave delicate nets to capture prey, or to filter food has given this “minor” order a prominent role in the study of insect behavior. It is this feature, the architectural habits of caddisfly larvae, that is the subject of a wonderful new book by Glenn B. Wiggins.

Wiggins long ago established himself as one of the world’s preeminent trichopterologists. His 1977 book, Larvae of the North American Caddisfly Genera (Trichoptera), also published by the University of Toronto Press and now in its 2nd edition (1996), was a masterpiece of scientific inquiry and scholarship; it was the seminal piece of literature that started and continues to inspire my career in caddisfly systematics. His new work, Caddisflies, the Underwater Architects, will certainly have a similar effect on current and future students of the group.

The book begins with an introduction that contains an inspiring, almost romantically written account of water, its unique qualities, its importance to life on Earth, and as habitat for Trichoptera. The remainder of the book is divided into three sections: Caddisflies in Ecosystems, the Families of Caddisflies, and Supplementary Information.

In Part I, Caddisflies in Ecosystems, Wiggins presents chapters on Architecture and Biology, Caddisflies in Freshwater Communities, Architecture of Pupation by Caddisflies, Evolution of Caddisflies and Their Architecture, Biogeography of Caddisflies, and an Epilogue, which provides the bulk of the scientific content of the book. These chapters are rich in content and are an encyclopedic source of information about all aspect of larval biology. The accounts of the different ways caddis larvae use silk to construct portable cases or fixed retreats with their accompanying capture nets are fascinating. Wiggins also provides a detailed review of the habitat and trophic diversity of larvae, which is couched in terms of modern stream ecological theory, including the River Continuum Concept.

Much of this information is from Wiggins’ own published research and observations, including his pioneering studies of caddisflies in temporary vernal pools and of pupation behavior (allotted an entire chapter), but he has taken the time to reinterpret his hypotheses on the basis of newly published information. For example, he presents evidence from newly published morphological as well as molecular phylogenetic analyses on the evolution of caddisflies and their construction behaviors. He rightly points out that an understanding of the relationships of the four families of the suborder Spicipalpia, cocoon-makers (itself equivocally monophyletic), and of the taxa with the strongly supported monophyletic suborders Annulipalpia, retreat-makers, and Integripalpia, case-makers, is key to understanding the basal radiation of the order and its biological attributes.

Wiggins’ comparison of previous phylogenetic analyses and their conclusions, however, is confounded by the different datasets (weighted toward adult, larval, behavioral, or molecular characters) and methods of analysis (Hennigian argumentation, compatibility analysis, equally weighted parsimony, noncladistic methods, etc.) used in the published phylogenies. Until a large dataset (in terms of characters and sampled taxa) is accumulated and analyzed by currently accepted modern methods, a firm understanding of caddisfly evolution remains a goal. As in his treatment of caddisfly evolution, I found most of his discussions to include new findings from the recent literature; a rare exception is the omission of recent important contributions by Stuart and Currie on caddisfly case making behavior and its use in phylogeny reconstruction.

Part II is a survey of the larvae of all 45 currently recognized families of Trichoptera. Each North American family is discussed, more or less comprehensively, in terms of its diagnostic characters, construction behavior, biology, and distribution, along with closing comments about its fossil history, taxonomy, or other interesting features. This section is fascinating reading for those enchanted by the morphological and behavioral diversity among organisms. The illustrations accompanying the section are outstanding (among the best in entomology, in my opinion) and were largely excerpted from the author’s previous works.

This section, however, is disappointing, given the comprehensive nature of the previous sections, in that it superficially treats the non-North American fauna. Those families not occurring in North America, except for a few extralimital families previously researched by the author (e.g., Phryganopsychidae, Limnocentropodidae) are treated only briefly and without accompanying illustrations, even through sufficient information exists about their biology and behavior. This is especially true of those families endemic to the southern continents. Granted, although Wiggins states his intent in the objectives of the book to treat comprehensively only this restricted fauna, where his expertise is rooted, he misses a golden opportunity: no such treatment, to the extent and skill that Wiggins provides for the North American fauna, exists for the world fauna. Similarly, the excellent keys he has provided to the larvae, adults, and pupae of the North American fauna have no equivalent for the world fauna. As such, as an identification resource, the book will be much less useful to non-North Americans, although it will be of use to inhabitants of the northern hemisphere, where the same families by and large occur.

The quality of the illustrations, diagrams, and charts, all in black and white except for a single color frontispiece, are excellent throughout the work. The detailed illustrations of caddisfly larvae and their wonderful cases will enthrall the viewer. The quality of the paper, printing, and binding are excellent. At $125, the cost may appear high, but given the physical quality of the work and its outstanding scholarship, it is worth the price.

Glenn Wiggins obviously has deep affection for caddisflies. His devotion to the study of Trichoptera has been expressed in this work and in the quality of his entire body of research. Here and elsewhere, he has given this “minor” order the recognition that it deserves.

Ralph Holzenthal
Department of Entomology
University of Minnesota
St. Paul, MN, 55108
holze001@umn.edu
American Entomologist
Vol. 52, No.3, Fall 2006