52 



The Rocky Mountain Locust. 



much less felt. In most sections visited, part of the 

 migrating hosts remained to lay eggs ; and the invasion 

 of 1876 is remarkable, as compared with that of 1874, for 

 the large extent of country supplied with eggs. Another 

 fact is noticeable, viz., that the very parts of Minnesota in 

 which eggs were laid in 1875, and the portions of Missouri 

 and Kansas in which they were most thickly laid in 1874, 

 escaped in 1876. I can not believe, however, that this is 

 anything more than coincidence. 



A careful review of the invasion, shows that it was made 

 up, 1st, of such insects as hatched out in Southwestern 

 Minnesota, and parts of Colorado, Wyoming and Dakota; 

 2nd, of additions to these from Montana and British 

 America. To what extent those in either of these cate- 

 gories were made up of the progeny from the insects that 

 left our country in 1875 we shall never be able accurately 

 to determine. The proportion of parasitized and diseased 

 insects that left Missouri, doubtless became less among 

 those which hatched and rose from the farther north and 

 west, and we may, I think, take it for granted that the 

 larger part of the swarms that reached Montana and 

 British America, laid eggs. In addition to the vast swarms 

 which invaded the Northwest from the south and southeast, 

 there were in 1875, as Prof. Dawson shows, others that 

 hatched in the Northwest, pouring from British America 

 into our Northwest territory. There were, in fact, in 

 Manitoba and large parts of the Northwest, two grand 

 opposing movements of the winged insects, which thus to 

 some extent replaced each other and coalesced about our 

 northern boundary. Bearing this in mind, we can under- 

 stand the increased area in the Northwest over which eggs 

 were laid that year, and from which the 1876 swarms had 

 their source. As no eggs were laid in Manitoba, while the 

 young are known to have abounded in the mountain region 



