GENERAL CROP PESTS 7I 



combined. Its range of injuriousness is not limited to the Rocky 

 Mountain region, but it is more abundant there than elsewhere. 

 It is illustrated in figure 40. Those who were interested in 

 farming in the 7o"s in Kansas, Nebraska, and some neighboring 

 states have cause to remember the depredations of the Rocky 

 Mountain locust. During 1874-1877 it was directly responsible 

 for the loss of $100,000,000, in addition to an indirect loss by 

 the stoppage of business and other enterprises which might 

 have aggregated as much more. It was for an investigation of 

 this species that the United States Entomological Commission 

 was formed, which published from 1877 to 1879 two voluminous 

 reports on it alone. 



The Differential Locust {Mclanoplus diffcrentialis ThomdLs). — 

 In the Middle West the farmer is much bothered at times by 



i\-—Melanoplus differenhalis- Natural size 

 (After Riley) 



the large yellow locust, shown in figure 41. It is found along 

 roadsides and on the edges of groves, preferring rank vegeta- 

 tion where such abounds. When it becomes unusually numer- 

 ous it is quite destructive to vegetable crops and to cereals. 



METHODS OF CONTROL 



Locusts or grasshoppers are largely kept within normal num- 

 bers by numerous enemies, among which are many large forms 

 of insectivorous birds and mammals, batrachians and reptiles. 

 They also have large numbers of predaceous and parasitic insect 

 enemies, which kill them off in ordinary seasons. With changes 

 of the weather, however, the insect enemies are frequently de- 

 stroved, and then the locusts become abundant. In such cases 



