Book excerpt: Written for students who have completed an introductory course in biology, the fourth edition of Daly and Doyen's Introduction to Insect Biology and Diversity presents the ideal balance of basic biological principles and in-depth treatment of insect classification, including keys for identifying more than four hundred families. In this fourth edition, James B. Whitfield, of the University of Illinois, Urbana-Champaign, continues as lead author, bringing a wealth of expertise on molecular analysis relating to development and systematics.