2 MISC. PUBLICATION 273, U. 8. DEPT. OF AGRICULTURE 
INTRODUCTION 
Protecting forests from destruction is the first ‘basic requirement 
in the practice of forestry. Important destructive agencies include 
not only fire but also insect pests, fungous diseases, animals, drought, 
flood, and wind. While damage from insects to timber is less spec- 
tacular than that caused by either fire or wind, timber losses from 
any of these three agencies may be of catastrophic magnitude. More- 
over, Insects are constantly at work in the forest and are the cause 
of a steady drain on timber supplies. To allow fire or insects to run 
unchecked in our forests is to invite disaster and seriously to threaten 
the present and future timber supply. 
Protection from fire has been given intensive study, and notable 
progress has been made in fire control. Less attention has been given 
to the control of timber- destroying insects, partly because practical 
control methods have not always been available and partly because 
the expense of applying them has not been warranted in view of cur- 
rent timber values. Moreover, practicing foresters in the West have 
been handicapped by lack of a convenient reference manual, and as 
a result have considered insect control a specialized subject with 
which only the entomologists were prepared to deal. With the new 
emphasis on forest conservation, there is, however, an increasing 
demand by foresters for information on insects, as this information 
is intimately related to many phases of forest protection and man- 
agement (fig. 1). 
Forest insects other than tree-killing species also present many 
special problems. They may be encountered in every operation, from 
the collection of seed through the planting, growing, and harvesting 
of forest trees, in the handling and protection of utilized wood prod- 
ucts, and even in the management of grazing lands. In all of these 
cases some special knowledge of the insects concerned and of their 
habits is required in order that suitable methods of prevention or 
control may be effectively applied. 
This field handbook has been prepared to meet this need. The dis- 
cussions 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 1s hoped that the information assem- 
bled will aid timber owners and foresters in recognizing the work of 
important western forest insects, in applying suitable control meas- 
ures, or in adjusting forest practices so as to reduce losses from this 
source to the lowest possible point. 
KINDS OF FOREST INSECTS AND THE LOSSES THEY 
CAUSE 
All forests are swarming with insect life. This insect population 
serves many functions and is as much an essential part of the com- 
plex association of living, growing, and dying organisms which we 
call the forest as are the trees themselves. 
Of the thousands of insect species found within our forests, many 
are harmless or even beneficial, A great many feed on dead trees and 
