I would say that creating an encyclopedia of insects was a herculean task, but I think that sells the enterprise short. After all, Hercules only had twelve labors assigned to him, and twelve years to complete them—with insects, there are over 900,000 different species and many, many more stories to tell. Twelve years from now, there will likely be even more. Why, then, would anyone undertake the seemingly impossible task of compiling an encyclopedia of insects? To an entomologist, the answer is obvious. For one thing, there's the numbers argument—over 70% of all known species are insects, so if any group merits attention in encyclopedic form, surely it's the one that happens to dominate the planet. Moreover, owing in large part to their staggering diversity, insects are in more different places in the world than virtually any other organism. There are insects in habitats ranging from the high Arctic to tropical rainforests to petroleum pools to glaciers to mines a mile below the surface to caves to sea lion nostrils and horse intestines. About the only place where insects are conspicuously absent is in the deep ocean (actually, in deep water in general), an anomaly that has frustrated more than a few entomologists who have grown accustomed to world domination. Then there's the fact that insects have been around for longer than most other highprofile life-forms. The first proto-insects date back some 400 million years; by contrast, mammals have been around only about 230 million years and humans (depending on how they're defined) a measly one million years.

Probably the best justification for an encyclopedia devoted to insects is that insects have a direct and especially economic impact on humans. In the United States alone, insects cause billions of dollars in losses to staple crops, fruit crops, truck crops, greenhouse and nursery products, forest products, livestock, stored grain and packaged food, clothing, household goods and furniture, and just about anything else people try to grow or build for sale or for their own consumption. Beyond the balance sheet, they cause incalculable losses as vectors of human pathogens. They're involved in transmission of malaria, yellow fever, typhus, plague, dengue, various forms of encephalitis, relapsing fever, river blindness, filariasis, sleeping sickness, and innumerable other debilitating or even fatal diseases, not just abroad in exotic climes but here in the United States as well. All told, insects represent a drag on the economy unequaled by any other single class of organisms, a seemingly compelling reason for keeping track of them in encyclopedic form.

In the interests of fairness, however, it should be mentioned that insects also amass economic benefits in a magnitude unequaled by most invertebrates (or even, arguably, by most vertebrates). Insect-pollinated crops in the United States exceed $9 billion in value annually, and insect products, including honey, wax, lacquer, silk, and so on, contribute millions more. Insect-based biological control of both insect and weed pests is worth additional millions in reclaimed land and crop production, and even insect disposal of dung and other waste materials, although decidedly unglamorous, is economically significant in fields, rangelands, and forests throughout the country.

So, for no reason other than economic self-interest, there's reason enough for creating an encyclopedia of insects. But what can be learned from insects that can't be learned from an encyclopedia of any other abundant group of organisms? Basically, the biology of insects is the biology of small size. Small size, which has been in large part responsible for the overwhelming success of the taxon, at the same time imposes major limits on the taxon. The range in size of living organisms, on earth at least, encompasses some 13 orders of magnitude (from a 100 metric ton blue whale to rotifers weighing less than 0.01 mg). Insects range over five orders of magnitude—from 30-g beetles to 0.03-g fairyflies—so eight orders of magnitude are missing in the class Insecta.

Problems at the upper limit involve support, transport, and overcoming inertia, issues clearly not critical for organisms, like insects, at the lower end of the range.

We humans, in the grand scheme of things, are big creatures and as a consequence we interact with the biological and physical world entirely differently. Rules that constrain human biology often are suspended for insects, which operate by a completely different set of rules. The constraints and benefits of small size are reflected in every aspect of insect biology. They hear, smell, taste, and sense the world in every other way with abilities that stagger the imagination. They are capable of physical feats that seem impossible—most fly, some glow in the dark, and others control the sex of their offspring and even occasionally engage in virgin birth, to cite a few examples. Their generation times are so short and reproductive rates so high that they can adapt and evolve at rates that continually surprise (and stymie) us. The environment is "patchier" to smaller organisms, which can divide resources more finely than can large, lumbering species. Thus, they can make a living on resources so rare or so nutrient-poor that it defies belief, such as nectar, dead bodies, and even dung.

So they're profoundly different from humans and other big animals, and the study of insects can offer many insights into life on earth that simply couldn't be gained from a study of big creatures. By the same token, though, they are cut from the same cloth—the same basic building blocks of life, same genetic code, and the like—and their utility as research organisms has provided insights into all life on the planet.

The Encyclopedia of Insects contains contributions from some of the greatest names in entomology today. Such a work has to be a collective effort because nobody can be an expert in everything entomological. Even writing a foreword for such a wide-ranging volume is a daunting task. To be such an expert would mean mastering every biological science from molecular biology (in which the fruit fly Drosophila melanogaster serves as a premier model organism) to ecosystem ecology (in which insects play an important role in rates of nutrient turnover and energy flow). But, because insects, through their ubiquity and diversity, have had a greater influence on human activities than perhaps any other class of organisms, to be the ultimate authority on insects also means mastering the minutiae of history, economics, art, literature, politics, and even popular culture. Nobody can master all of that information— and that's why this encyclopedia is such a welcome volume.

Insects are ever present in human lives. They are at once awe inspiring, fascinating, beautiful, and, at the same time, a scourge of humans because of food loss and disease. Yet despite their negative effects, we depend on insects for pollination and for their products. As insects are the largest living group on earth (75% of all animal species), any understanding of ecological interactions at local or global scales depends on our knowledge about them. Given the current interest in biodiversity, and its loss, it must be remembered that insects represent the major part of existing biodiversity. Aesthetically, insect images are often with us as well: early images include Egyptian amulets of sacred scarabs; modern images include dragonfly jewelry, butterfly stationery, and children's puppets.

The idea of an Encyclopedia of Insects is new, but the concept of an encyclopedia is quite old. In 1745, Diderot and D'Alembert asked the best minds of their era—including Voltaire and Montesquieu—to prepare entries that would compile existing human knowledge in one place: the world's first encyclopedia. It took over 20 years to finish the first edition, which became one of the world's first best-selling books and a triumph of the Enlightenment.

What do we intend this encyclopedia to be? Our goal is to convey the exciting, dynamic story of what entomology is today. It is intended to be a concise, integrated summary of current knowledge and historical background on each of the nearly 300 entries presented. Our intention has been to make the encyclopedia scientifically uncompromising; it is to be comprehensive but not exhaustive. Cross-references point the reader to related topics, and further reading lists at the end of each article allow readers to go into topics in more detail. The presence of a certain degree of overlap is intentional, because each article is meant to be self-contained.

The Encyclopedia of Insects also includes organisms that are related to insects and often included in the purview of entomology. Therefore, besides the members of the class Insecta—the true insects—the biology of spiders, mites, and related arthropods is included. The core of this encyclopedia consists of the articles on the taxonomic groups—the 30 or so generally accepted orders of insects, the processes that insects depend on for their survival and success, and the range of habitats they occupy. The fact that entomology is a dynamic field is emphasized by the discovery of a new order of insects, the Mantophasmatodea, just as this encyclopedia was being completed. This is the first order of insects to be described in over 80 years, and we are pleased to be able to include it as an entry, further underscoring that there is much left to learn about insects. Some topics, especially the "poster insects"—those well-known taxa below the level of orders for which entries are presented—may not cover all that are desired by some readers. Given insect biodiversity, your indulgence is requested.

We have gathered over 260 experts worldwide to write on the entries that we have selected for inclusion. These specialists, of course, have depended on the contributions of thousands of their entomological predecessors. Because the modern study of entomology is interdisciplinary, we enlisted experts ranging from arachnologists to specialists in zoonotic diseases. Given that the two of us have spent over 25 combined years as editors of the Annual Review of Entomology, many of our contributors were also writers for that periodical. We thank our contributors for putting up with our compulsive editing, requests for rewrites, and seemingly endless questions.

Our intended audience is not entomological specialists but entomological generalists, whether they be students, teachers, hobbyists, or interested nonscientists. Therefore, to cover the diverse interests of this readership, we have included not just purely scientific aspects of the study of insects, but cultural (and pop-cultural) aspects as well.

We thank the staff of Academic Press for their encouragement and assistance on this project. Chuck Crumly had the original concept for this encyclopedia, convinced us of its merit, and helped us greatly in defining the format. Chris Morris provided suggestions about its development. Jocelyn Lofstrom and Joanna Dinsmore guided the book through printing. Gail Rice managed the flow of manuscripts and revisions with skill and grace, and made many valuable sug-

gestions. Julie Todd of Iowa State University provided a crucial final edit of the completed articles. All these professionals have helped make this a rewarding and fascinating endeavor.

We dedicate our efforts in editing the Encyclopedia of Insects to our wives, Cheryl and Anja; their contributions to our entomological and personal lives have been indescribable.

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