Food Uptake and Utilization

Abstract

The strongly favorable reception accorded previous versions of this book, together with the not infrequent urgings of colleagues and students, encouraged me to take on the task of preparing a third edition of Entomology. My early retirement, in 1999, freed up the time necessary for a project of thissize, andfor the past 2 yearsmyeffort has been almost entirely focusedinthis direction. Obviously, all chapters have been updated;this includes not only the addition of new information and concepts (some of which are highlighted below), but also the reduction or exclusion of material no longer considered ‘mainstream’ so as to keep the book at a reasonable size. My strong belief that an introductory entomology course should present a balanced treatment of thesubject still holdsandisreflectedinthe retention of the format of earlier editions, namely, arrangement of the book into four sections: Evolution and Diversity, Anatomy and Physiology, Reproduction and Development, and Ecology. Section I (Evolution and Diversity) has again undergone a great reworking, mainly because the last decade has seen the uncovering of significant new fossil evidence, and the application of molecular and cladistic analyses to extant groups. As a result, ideas both on the relationships of insects to other arthropods and on the higher classification of many orders have changed drastically. However, as in previous editions, I have stressed that most phylogenies are not ‘embedded in stone’ but represent the consensus based on existing information; thus, they are liabletorefinement as additionaldata are forthcoming. Chapter 1 discusses theevolution of Insecta inrelation to other arthropods, emphasizing theageless debate on whether arthropods form a monophyleticorpolyphyletic group, and the relationship of insects to other hexapodous arthropods. Evolutionary relationships within the Insecta are considered in Chapter 2, together with discussion of the factors that contributed to the overwhelming success of the group. Chapter 3 serves two purposes: It provides a description of external structure, which remains theprincipalbasisonwhich insects can beclassified andidentified,while stressingdiversitywith reference to mouthpart and appendage modifications. In Chapter 4 the principles of classification and identification are outlined, and a key to the orders of insects is provided. Diversity of form and habits is again emphasized in Chapters 5 to 10, which deal with the orders of insects, including the Mantophasmatodea, established only in 2002. For many orders, new proposed phylogenies are presented,and thetext has undergone significant rearrangement to reflect modern ideas on the classification of these taxa.The chapters in Section II (Anatomy andPhysiology) deal with the homeostatic systems of insects; that is, those systems that keep insects ‘in tune’ with their environment, enabling them to develop and reproduce optimally. The section begins with a discussion of the in- tegument (Chapter 11), as this has had such a profoundinfluence on the success ofinsects. Chapter 12 examines sensory systems, whose form andfunction are greatly influencedby the cuticular nature of the integument. InChapter 13,where neural and chemicalintegration are discussed, new sections on kairomones and allomones have been included. Chapter 14 considers muscle structure and function, including locomotion. In this chapter the section on flight has been significantlyrevised, especiallywith respect to recent proposals for the generation of lift using non-steady-state aerodynamics. Chapter 15 reveals the remarkable efficiency of the tracheal system in gaseous exchange, and Chapter 16 deals with the ac- quisition and utilization of food. Chapter 17 describes the structure and functions of the circulatory system, including the immune response of insects about which much has been learned in the past decade. New to this chapter is a section on how parasites and parasitoids are ableto defend themselves against the host insect’s immunesystem.Chapter 18 concludes this section with a discussion of nitrogenous waste removal and salt/water balance. In Section III reproduction (Chapter 19), embryonic development (Chapter 20), and postembryonic development (Chapter 21) are discussed. Chapter 19 includes additional information on behavioral aspects of reproduction (courtship, mate guarding and sexual selection), as well as sperm precedence. Chapter 21 has been revised to provideanupdated account of theendocrine regulation ofdevelopment and molting. Section IV (Ecology) examines those factors that affect the distribution and abundance of insects. In Chapter 22 abiotic (physical) factors in an insect’s environment are considered. Chapter 23 deals with the biotic factors that influence insect populations and serves as a basis for the final chapter, inwhich thespecific interactions ofinsects andhumans are discussed.Of all of thechapters, Chapter 24 has received the most drastic overhaul; such has been the ‘progress’ (and the costs of such progress) inthe battleagainst insect pests. Asmay be inferred from the opening paragraph of this Preface, the book is intended as a text for senior undergraduates takingtheir first course in entomology.Suchstudents probably will haveanelementary knowledge ofinsects acquiredfrom an earlier course in general zoology,aswell as a basicunderstanding of animal physiology and ecological principles. With such a background, students should have no difficulty understanding the text. Preparation of the third edition has benefited, not only from both published and un- solicited reviews of previous editions, but also from my solicitation of comments on the content of specific chapters from experts in those areas. Of course, any errors that remain, and I hope these are extremely few, are my responsibility. I have enjoyed preparing this third edition, for it has given me, once again, the opportunity to delve into aspects of ento- mology that are well outside the range of an ‘insect sexologist’. For example, I never cease to be impressed by the remarkable discoveries and insights of those entomologists who deal with fossil insects, by those who develop integrated strategies for the management of insect pest populations, andbythe patience anddedication (and imagination—see Chapter 4, Section 2) ofinsect taxonomists. Hopefully, readers of thenewedition will receive the same enjoyment.