It was gratifying to be invited to prepare a third edition of this book, which first appeared in 1951. Preliminary discussions with the publishers, however, revealed a considerable challenge in the present high costs of printing, so that changes and some improvements were clearly necessary to justify the venture. It was immediately apparent that the chapter on chemical control measures would have to be substantially re-written, because of the great changes in usage due to resistance and the regulations introduced to prevent environmental pollution. Also, I decided to expand the scope of the book by increased coverage of the pests of continental Europe and North America, including some new figures and keys in the Appendix. These two undertakings resulted in considerable expansion in length, with about 370 new references and 250 additional specific names in the Index. In order to avoid too alarming an increase in price, I decided to sacrifice three chapters from the earlier editions: those dealing with the structure and classification of insects, their anatomy and physiology, and their ecology. Readers who require basic biological information on insects should buy one of the various short introductions to entomology available.