58 



The Rocky Mountain Locust. 



may suffer from swarms from the mountain regions farther 

 south, it seems quite certain that the extensive and disas- 

 trous swarms which come late in summer and fall, and 

 which reach as far east as Missouri, have their origin in the 

 vast plains regions of the Northwest lying east of the 

 mountains, in Montana, Dakota, and the Saskatchawan 

 and Red River countries of British .America.* Some wri- 

 ters find it difficult to believe that the insect can fly over 

 such immense distances, and they believe that the swarms 

 originate (as Mr. S. H. Scudder, of Cambridge, puts it), 

 " in the immediate vicinity of the regions which they 

 devastate." 



Such language is not very definite, since much of the 

 country devastated must be in the immediate vicinity of 

 the hot, dry plains and plateaus in which I believe the 

 species is more particularly at home. The swarms that 

 occasionally, during summer, devastate the country in 

 which the species is not indigenous, must necessarily be 

 the progeny of insects developed at no great distance 

 from the sections they invade, whether they come from 

 Minnesota southward, from Colorado eastward, or from 

 Texas northward ; and I endeavored to draw the distinc- 

 tion in 1874 between these summer swarms and the more 

 disastrous fall swarms. On this point the Minnesota 

 commission remarks (Special Rep. to Gov. Davis, p. 25) : 



It is plain that locusts hatched in Colorado and regions to the 

 south and southwest of Minnesota, acquire wihgs in lime to allow 

 them to reach t bis State in the former half of June. This is shown 

 by the time when the invasion occurred in 1873, and by the immense 

 flights of locusts which passed over Nebraska and Dakota to the 

 northward in June, 1875. It seems to be a common impression that 

 the locusts which have invaded Minnesota at other times were 

 hatched in Montana, Northwestern Dakota and British America, 

 and this is rendered probable by what few facts we know r , and by 



* The origin of the swarms that devastate the Pacific slope is probably in 

 the similar high plains regions of Washington, Idaho and Oregon. 



