This field handbook has been prepared to provide information on western forest insects. The discussions are limited to the insects and the problems which they raise in the management and protection of the forests of the Western States, although the general principles of control are applicable to other forest regions as well. It is hoped that the information assembled will add timber owners and foresters in recognizing the work of important western forest insects, in applying suitable control measures, or in adjusting forest practices so as to reduce losses from this source to the lowest possible point.

The investigations by the United States Government of the insects affecting forest trees, forest products, and shade trees are centered in the division of forest insects of the Bureau of Entomology. The investigations carried on by the division are grouped for administrative convenience into projects, the most important of which are briefly described in the following paragraphs.