﻿OF THE STATE ENTOMOLOGIST. Ill 



do notfore;et its irregularity in the same locality, and refer in conse- 

 quence to the bulk of the eggs. The invasion of northern regions, 

 like Minnesota and Dakota, from the still further northwest, makes it 

 also clear that the insects come from beyond. The theory of short 

 flights and development, in the immediate vicinity of the country 

 devastated, will scarcely answer for the late disastrous and general 

 irruptions like those of 1866 and 1874 ; and in discussing this question 

 the difference between these irruptions and the earlier, more frequent 

 and less disastrous ones, should always be borne in mind. 



[3J I deny that the species, as defined in these reports, and as it 

 swoops down from the mountain region, occurs every year in Missouri, 

 Texas, Kansas, or any of the country to which I have indicated it is 

 not indigenous. It occurs there only as the dwindling progeny of the 

 swarms from the west or northwest, and never becomes acclimated. I 

 have traveled through Iowa, and from Omaha to Denver, collecting 

 plants and capturing insects along the route on every occasion ; I 

 have traveled extensively in Kansas, Indian Territory and Texas, al- 

 ways collecting ; I have been overwhelmed in the latter State with 

 swarms of locusts while in front of an engine, and yet, among all the 

 locusts collected, I have never found the genuine spreius. It cannot 

 be found there any more than it can be found in our western counties, 

 except as the progeny of invading swarms. There is no instance on 

 record of the species, when hatching out in any of this country, re- 

 maining long enough to lay eggs, even supposing it capable of doing 

 so under such circumstances. We find it multiplying continuously 

 west and north of the boundary indicated ; pushing annually, in de- 

 tachments, eastward from the mountains to the west, and southeast- 

 ward from the country to the northwest ; but only at long intervals 

 does it sweep down in countless myriads and extended and devastat- 

 ing swarms from the extreme northwest. Just beyond the confines of 

 the country in which it permanently multiplies, it follows that it will 

 more often do injury than farther east and south ; it will also hold its 

 own longer, but sooner or later it vanishes from the country beyond 

 those confines. It either vacates the territory on the wing or is de- 

 stroyed by influences adverse to its well-being. 



In placing these confines along the 41th parallel and 100th merid- 

 ian, I think I have given the utmost southern and eastern limit. Prof. 

 Thomas indicates the eastern boundary as along the 103rd meridian, 

 while Mr. G. M. Dawson, in the pamphlet already referred to, says that 

 " north of the 49th parallel, the whole area of the third or highest 

 prairie-plateau, and probably much of the second, are congenial 

 breeding places, and here the locusts are always in greater or less 



