﻿OF THE STATE ENTOMOLOGIST. 79 



not seem to have been durino^ this period any remarkable persistency of northwest 

 or northerly winds, the insects must have selected those favoring their intended direc- 

 tion of migration, an instinct which has very generally been observed elsewhere. 



Foreign swarms from the south crossed the 49th parallel with a wide front stretch- 

 ing from the 98th to the lOSth meridian, and are quite distinguishable from those pro- 

 duced in the country, from the fact that many of them arrived before the latter were 

 mature. These flights constituted the extreme northern part of the army returning 

 northward and northwestward from the States ravaged in the autumn ot 1874. They 

 appeared at Fort EUice on the 13th of June, and at Qu'Appelle Fort on the 17th of 

 the same month, favored much no doubt by the steady south and southeast winds, 

 which, according to the meteorological register at Winnipeg, prevailed on the 12th of 

 June and for about a week thereafter. Afcer their first appearance, however, their sub- 

 sequent progress seems to have been comparatively slow, and their advancing border 

 very irregular in outline. They are said to have reached Swan Lake House — the most 

 northern point to which they are known to have attained — about July 10; while Fort 

 Pelly, further west, and nearly a degree further south, was reached July 20th, and 

 about seven days were occupied in the journey from there to Swan River Barracks, a 

 distance of only ten miles. 



We thus learn that vast swarms not only reached into British 

 America in 1875, from our own country, but that the young hatched 

 there from swarms that had come the previous year from the further 

 northwest. 



There was, therefore, north of the 49th parallel, a repetition of 

 the devastation we were at the time experiencing; the insects hatch- 

 ing there in bulk just about the time they were leaving Texas on the 

 wing. 



SOURCE OF THE SWARMS OF 1876. 



From the preceding statement of facts, and from the detailed 

 history of the invasion of 1876, it becomes obvious that this invasion 

 was made up, let, of such insects as hatched out in southwest Minne- 

 sota, and parts of Colorado, Wyoming and Dakota; 2d, of additions 

 to these from Montana and British America, In how far those in 

 either of these categories 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 bevies 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 replaced each 

 other. And bearing this in mind, we can understand 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 moun- 



