Possibly the development most significant for agricultural entomology which has taken place since this book was first published is the preparation of the new insecticides D.D.T. and Gammexane. Since the application of these substances to the control of insect pests of agricultural crops has as yet hardly begun it is difficult to say how successful they will be. So far as they have been tried they seem to show great promise and I have endeavoured to indicate each case where success has been achieved.

The bulk of the book remains unchanged but any new facts concerning life-histories and control methods have been incorporated so far as possible.

The study of the insect-borne virus diseases affecting agricultural crops has made great strides and in consequence Chapter xiv has been entirely re-written and some new illustrations added. I am indebted to my colleague Dr Roy Markham for taking the photographs for Figs. 82, 84.

A book of the nature of the present volume must necessarily be something of a compilation, and in preparing it I have made free use of the many papers on entomology which have appeared in the various scientific journals. I have, however, endeavoured to make acknowledgment of the source of any new or important facts and observations which I may have quoted. In surveying this literature the invaluable aid rendered by the Review of Applied Entomology must be mentioned.

Special acknowledgment is due to my sister, Faith Blomfield Smith, for her care and skill in reproducing many of the figures borrowed from other sources and for making, the original illustrations of Figs. 13-18, 20-22, 40 and 43.