INSECTA 



89 



of grasshoppers already infected with contagious diseases. 

 Several years ago a plague of locusts was successfully fought 

 in Argentina by liberating a fungous disease. More 

 recently in New Mexico a fly, Sarcophaga kellyi, "was 

 found to be by far the most important factor in control." 

 Some wild birds (horned lark, meadow lark, sparrow hawk, 

 kildeer, quail) also served as loyal allies of man on this 

 occasion. 



The great "plagues" of grasshoppers in the United States 

 have in most cases been due to the ravages of the migratory 

 locust, Melanopus spretus, which travels in enormous flocks 



FIG. 43. A hopperdozer. Kerosene is placed in the trough which is then 

 dragged over a field. 



through the high prairies of Western Kansas, Nebraska, and 

 Eastern Colorado. In the plague of 1913, another species, 

 Dissostera longipennis, was so abundant that it repeatedly 

 stopped trains by massing on the railroad tracks. It 

 rendered an area of 500 square miles unfit for grazing. 

 Grasshoppers not only harm man by feeding on crops, 

 but do injury by spreading the spores of various plant 

 diseases. 



If a grasshopper successfully escapes all its enemies, it 

 still cannot rest in idle ease, but must make continual 

 adjustments to the changing conditions in its surroundings. 

 During rains the big head and roof-like wings protect it 



