iv INTRODUCTION 



The extent of insect injuries in the United States has 

 been carefully estimated by experts in the U. S. Department 

 of Agriculture and these estimates place the total annual 

 loss at not far from the stupendous sum of one billion 

 dollars. This estimated loss is divided among various 

 classes of products. Of these, grain and forage crops are 

 the heaviest sufferers, bearing about one-third of the total; 

 the live stock industry assumes another third; truck 

 crops stand one-sixth the total loss. After these come, 

 with smaller totals, cotton, fruit, tobacco, forests and mis- 

 cellaneous products. 



In addition to the tangible monetary losses occasioned 

 by the activities of the insects which attack crops, must 

 be considered the less definite, but none the less real, im- 

 portance which is based on their disease-carrying faculties, 

 the study and knowledge of which has been confined to 

 the more recent years. 



No one can estimate the actual importance of the mos- 

 quitoes in terms of dollars. The money loss to the nation 

 in any year from malaria is undoubtedly great, but the 

 importance of the insects which transmit it from one 

 person to another would not be based on the consideration 

 of money at all. Nor is the comfort of the inhabitants 

 of the mosquito-ridden lands a financial problem, primar- 

 ily, although land values undoubtedly increase rapidly 

 when the mosquito-breeding places are destroyed. 



The house-fly, carrier of filth as it has long been known 

 to be, and carrier of disease from a more recent convic- 

 tion, likewise is not a problem of the pocketbook. Both 

 are, in the larger sense, problems of the higher civiliza- 

 tion, and both add to the importance of the study of 

 insects and present this in an entirely different light than 

 the one of the billion dollar annual loss. 



