The Lepidopters (moths and butterflies) are one of the largest groups of insects with over 150,000 named species. This book deals with their structure and function, environmental significance, and diversity. Part I provides a review of the main body parts with discussion of function and importance in the lifestyle of the organisms. Further chapters cover feeding, flight, migration, hearing, sound production, defence, and many other aspects of lepidopteran life. The environmental significance of Lepidoptera, which is summarized in Part II, is discussed mainly in terms of larvae as herbivores and as prey. In part III, the author provides a global conspectus of the Lepidopters. He describes the adults and immature stages of each family, and summarizes their biology, classification, and evolutionary relationships within and between groups. This book will be an indispensable reference work for naturalists, professional entomologists, and conservationists for years to come.