BREEDING GROUNDS OF THE LOCUST. 131 



CHAPTER V. 



perma:n^ent breeding grounds of the rocky 

 mountain locust. 



Previous to the year 1877 our knowledge of the extent of the breed- 

 ing grounds of the Rocky Mountain locust {Caloptenus spretus) was vague 

 and unsatisfactory. It was known that the swarms invading the Mis- 

 sissippi Yalley mainly came from portions of Wyoming, Montana, and 

 the region in British America lying north of this territory, but to attempt 

 to map out the area and to determine its extent was impossible. From 

 the data obtained, either directly by the Commission or from its corres- 

 pondents, we are enabled to present a more or less definite statement 

 regarding the extent of the region, and to indicate it upon a map, which, 

 besides showing the geographical distribution of the species and its 

 migrations, indicates the annual or permanent breeding grounds of this 

 locust, its less permanent or subpermanent breeding grounds (Subper- 

 manent Region), and the region only periodically visited, i. e., the Tem- 

 porary Region. 



PERMANENT REGION. 



The area in which the locust breeds each year in greater or less num- 

 bers is approximately 300,000 square miles ; further explorations may 

 increase this area, particularly in Idaho and Montana. 



It is not to be inferred that the locust breeds continuously over the 

 whole extent of this area each year, as it is to be understood that the 

 locust within its native, permanent habitat is essentially migratory in 

 its habits, and while for a series of years it may deposit its eggs in a 

 given river valley, in some park, or in some favorable area on the 

 plains lying about the mountains; in a certain year, or for several 

 years in succession, it may desert its customary breeding grounds for 

 adjoining regions, or cross a low range of mountains and breed in a 

 more distant valley. Moreover, the true breeding grounds in this area 

 are for the most part confined to the river bottoms, or sunny slopes of 

 uplands, or to the subalpine grassy areas among the mountains, rather 

 than continuously over the more elevated, dry, bleak plains. For ex- 

 ample, over the great range of the plains east of the mountains, where 

 the buffalo grass alone grows, we have no evidence that the larger 

 swarms originate, and where they do, at times, it will be probably found 

 that the locusts hatched in the prairie land bordering the streams in- 

 tersecting the plains, rather than on the drier, less fertile plains them- 

 selves. In Central Montana the breeding grounds are, for example, 



