4 INTRODUCTION 
mated. By far the greater part of the annual toll goes unrecorded, — 
often unnoticed. Each season every crop on every farm pays its tax, 
whether large or small, to the busy, six-footed creatures that look to it 
for food. It is only when we stop to consider what this total must be, 
reckoned as a percentage of the value of all crops combined, that its 
tremendous proportions become evident. 
The best observers agree that, in the average, insect depredations 
equal at least 10 per cent of the value of all farm crops. Our agricul- 
tural products in this country have now reached an annual worth of 
$10,000,000,000. The total damage wrought by insects, therefore, may 
fairly be placed at $1,000,000,000 cach season! This is nearly five 
times as great as the combined appropriations for the United States 
army and navy; is equal to the entire bonded debt of the United 
States; is more than four times the annual property loss by fire; more 
than fourteen times the annual income of all colleges in this country ; 
is sixty times greater than the funds allotted annually to the United 
States Department of Agriculture. 
Value of a Knowledge of Insects 
Unquestionably, the loss due to insect attack may be reduced ma- 
terially by the adoption of proper methods of prevention and control. 
In many cases, the program to adopt involves no direct fighting, such as 
spraying, but simply the shaping of farm, garden, or orchard practice 
along lines unfavorable to the insects concerned — such matters as 
judicious rotation of crops, or cleaning fields of weeds. To-day’s 
warfare against insect pests strives toward prevention as well as cure. 
In order to plan our campaign intelligently we need to know the 
more important general facts about insects as a class: the main charac- 
teristics of the different groups with which we have to deal; how they 
have fitted themselves to survive and multiply; what measures of 
control are adapted to particular groups; how the structure and habits 
of one group render it susceptible to certain kinds of control measures, 
such as spraying, while in other groups wholly different measures are 
necessary. To know these general facts is to possess a fundamental 
advantage in conducting successful warfare. Not to know them usu- 
