320 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



guid than it otherwise would be 5 yet it seldom dies till the maggots 

 have left. Often in pulling off the wings of such as were hopping about, 

 the bodies have presented the appearance of a mere shell filled with 

 maggots J and so efficient is this parasite that the ground in parts of the 

 Western States is often covered with the Rocky Mountain locust dead 

 and dying from this cause. 



" Mr. Byers, in speaking of the locusts hatching in Colorado in 1865, 

 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. S. E. Wilber, of Greeley, Colo., has published an account of what 

 is evidently the same fly.*^^ In this account, after showing how persist- 

 ently the fly pursues the locust — leaving it no rest, and so effectually 

 weakening 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.'^ We have already expressed our 

 belief that at times they may prove one of the immediate causes. 



Persons who have not lived in the West, where the locust has pre- 

 vailed, can form no idea of the great abundance of these Tachina flies. 

 We found them buzzing about so numerously in the mountain regions 

 last summer as to prove a positive nuisance to travelers, and every 

 locust as it attempted to fly was pursued by several. It was also very 

 generally conceded, especially in Colorado, that one of the principal 

 reasons why the locusts did so little damage in 1877 was because they 

 were so generally infested with Tachina maggots. We found the same 

 state of things wherever we went in the Northwest, and in 1875 in parts 

 of Manitoba, as we were credibly informed by Mr. W. F. Luxton and 

 others, they so effectually killed off the young locusts that none matured 

 to fly off. In Minnesota they were so numerous as to follow the locusts 

 in vast swarms. Mr. J. I. Salter, of Stearns County, having communi- 

 cated the fact of vast clouds of flies passing over Todd County, we wrote 

 to ascertain the kind, and received the following account: 



As to the flies, they were the fly described in your bulletin as the Tachina-fly. Some 

 two or three weeks before the final flight of the 'hoppers I noticed thousands of those 

 flies on my timothy and clover meadow, where the locusts were in great numbers, and 

 noticed that these seemed to be in fear, restless, and uneasy. I found, by watching, 

 that they, had cause to be, for no sooner would one take wing, or even hop, but it 

 would be attacked by those flies. Finally, the locusts rose en masse and left, and shortly 

 after (I have now forgotten how soon) the flies left in a cloud or swarm, nearly all. I 

 saw the locusts leave ; also the flies. Then about the last flights of locusts, going 



'8 Popular Science Monthly, iv, p. 745. 



