ORTHOPTERA 



255 



Fig. 280. — Melanopliis 

 Riley.) 



bivittatus. (From 



The permanent home or breeding grounds of this species is in the 

 high, drylands on the eastern slope of the Rocky Mountains, extend- 

 ing from the southern limit of the true forests in British America 

 south through Montana, Wyoming, the western part of the Dakotas, 

 and the Parks of Colorado. There are also regions in which the species 

 exists permanently west of 

 the Rocky Mountains in 

 Idaho and Utah. 



When the food of this 

 insect becomes scarce in its 

 mountain home, it migrates 

 to lower and more fertile re- 

 gions. Its long wings en- 

 able it to travel great dis- 

 tances; and thus the larger 

 part of the region west of the Mississippi River is liable to be invaded 

 by it. Fortimateiy, the species cannot long survive in the low, moist 

 regions of the valleys. Although the hordes of locusts which reach 

 these sections retain their vigor, and frequently consume every bit 



of green vegetation, the yoimg, which 

 hatch from the eggs that they lay, perish 

 before reaching maturity. In this way 

 the invaded region is freed from the pest 

 until it is stocked again by another in- 

 cursion. There is, however, a large sec- 

 tion of country lying immediately east of 

 the great area indicated above as the 

 permanent home of this species, which it 

 frequently invades and in which it can 

 perpetuate itself for several years, but 

 from which it in time disappears. This 

 sub-permanent region, as it has been 

 termed, extends east in British America 

 so as to include nearly one-third of Mani- 

 toba; and, in the United States, it em- 

 braces nearly the whole of the Dakotas, 

 the western half of Nebraska, and the 

 northeast fourth of Colorado. 



The temporary region, or that only 



periodically visited and from which the 



Fig. 281 . — Melanoplits bivitia- species generallv disappears within a year, 



(FVom iS^ e/) ^ ^^"^"''- extends east and south so as to include 



" ^' more than half of Mitmesota and Iowa, 



the western tier of counties of Missouri, 



the whole of Kansas and Oklahoma, and the greater part of 



Texas. The coimtry lying east of the section thus indicated has 



never been invaded by this locust, and there is no probability that 



it will ever be reached by it. 



