Natural Enemies. 



133 



be a perfect fly, it is seen that it would take but a few generations 

 to clean out an army of grasshoppers. — [Oscar J. Strong, Eolfe, 

 Pocahontas County, Iowa, in Western Farmer, Feb., 1869. 



Mr. Byers, in speaking of the locusts hatching in Colo- 

 rado in 1865, (loc. cit.) says : " That upon attaining about 

 half their full size, they were attacked by a fly, which, 

 stinging them in the back between the roots of the wings, 

 deposited one or more eggs, which produced a large white 

 maggot. The worm subsisted upon the grasshopper, finally 

 causing its death, when it cut its way out and entered the 

 earth. In this way probably half were destroyed, often 

 covering the ground, and filling the furrows in plowed 

 fields with their carcasses. The remainder, when their 

 wings were sufficiently developed, took to flight, moving 

 southeast, and we lost trace of them on the great Plains." 



Mr. J. W. Crow, of Bigelow, Mo., in his correspondence 

 with me, describes these maggots as infesting the " hop- 

 pers" in Holt county in the fall of 1876 ; and in 1869 I 

 received the parasite from John P. Dopf, of Rock Port, 

 Atchison County, Mo., and have bred it from the Differen- 

 tial Locust, figured further on, and from the Carolina Lo- 

 cust ((Edipoda Carolina, L.) in St. Louis County. 



Finally, Mr. S. E. Wilber, of Greeley, Col., has published 

 an account of what is evidently the same fly.* In this 

 account, after showing how persistently the fly pursues 

 the locust — leaving it no rest, and so effectually weaken- 

 ing whole swarms as to render them harmless — he expresses 

 the opinion that the constant importunities and annoyances 

 of this fly are the cause of locust migrations. While, 

 however, they may constitute a factor in the result, such a 

 conclusion is too sweeping. 



The Yellow-tailed Tachina-fly (Exorista flavicauda, Ri- 

 ley, Fig. 32) which is so useful in destroying the Army- 



* Popular Science Monthly, IV, p. 745. 



