Xll INTRODUCTION 



In America, too, before the advent of Europeans, the Indians were 

 acquainted with insects that injured their corn fields, and during the 

 seventeenth and eighteenth centuries the crops of the early settlers were 

 seriously ravaged by "canker worms" and grasshoppers. One may say, 

 therefore, with Webster: "the actual economic element in entomology 

 is inevitably as old as Agriculture itself." On account, however, of the 

 ignorance and superstition that prevailed even among the learned 

 classes regarding the nature and habits of insects, no progress in the 

 control of insect pests was made or was possible until the latter half of 

 the nineteenth century. The introduction of rational methods of 

 control had to wait until considerable advance had been made in the 

 classification of insects and in a knowledge of their structure, habits and 

 life-history. 



In so far as America is concerned, it may be said that outbreaks of 

 certain insects, viz., the Rocky Mountain locust, the cotton worm 

 and the Colorado potato beetle during the last quarter of the nineteenth 

 century produced wide-spread attention to the great losses caused by 

 them, and forced the U. S. government at that time to appoint a 

 commission of entomological specialists for the purpose of investi- 

 gating the conditions. It was during this period that some of the 

 modern insecticides and improved spraying machinery were introduced, 

 Paris green becoming the standard remedy against the Colorado 

 potato beetle and the cotton worm, and kerosene emulsion against 

 sucking insects. The reports of Harris, Fitch and Riley, especially 

 those on the Rocky Mountain locust laid the foundation for future 

 ecological studies when the relations of injurious insects to other 

 organisms and to external factors were closely investigated. 



About the beginning of this century the San Jose scale and the 

 cotton boll-weevil threatened two important industries, and as a result 

 of the investigations many advances were made in the use of spraying 

 machinery and insecticides, notably lime-sulphur wash and hydrocyanic 

 acid gas, and in the application of biological processes and principles. 



In the attempt to solve the problem of the control of the gypsy and 

 brown-tail moths during the last twelve years another very important 

 advance was made toward a better understanding of parasitic insects 

 and of the part they are likely to play in the control of insects in the 

 future. Regarding the outlook of fighting insects along this line Dr. 

 Howard says: "There will be a very considerable development of this 



