26 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



flights from the south are recorded in July, passing over the O^^press 

 Hills region in Northwest Territory, and reaching the North Saskatch- 

 ewan at a few points, and even passing some distance north of Fort 

 Oarleton, yet from the want of data in the intermediate country we 

 cannot say positively that these were continuations from our side the 

 boundary-line, though the probability is that they were. The evidence 

 — and it is very complete — indicates that some of the swarms that went 

 northward the past season, through Minnesota and Dakota east of the 

 Missouri, penetrated north of the boundary -line ; but we know from the 

 history of 1875, and from the experience of the Hon. Donald Gunn, of 

 Winnepeg (App., 11), that the return migration does at times reach 

 beyond said line, and that the insects often pass from the south over 

 Manitoba during the month of June, or so early as to imply develop- 

 ment several degrees south of that province. 



The question as to what eventually became of these northward-return- 

 ing swarms was everywhere asked during the summer. The evidence 

 is clear that, as in previous years, these returning insects were mostly 

 so diseased and parasitized that they dropped in scattered numbers and 

 perished on their northward and northwestward journey. This is no 

 theory, but known to have been the case in the more thickly settled 

 parts of Kansas, Nebraska, Iowa, and Minnesota, from which the in- 

 sects that dropped were reported, and in some cases sent to us. Mr. J. 

 G. Kittson, of Fort Walsh, Cypress Hills, British America, also reports 

 that those which alighted there gradually disappeared without taking 

 further flight, and that they were badly attacked by parasites (App. 

 11). As this return flight is principally over a vast plain and prairie re- 

 gion that is thinly settled, the number of insects that dropped and were 

 lost to sight in said plains must have been infinitely greater than that 

 which was observed to come down in the more thickly settled regions 

 to the east. We found the insects sparsely spread over the rank prairies 

 west of Brainerd, along the Northern Pacific, and along Eed River, and 

 by this we mean that a few would hop from the grass at every step 

 wherever we searched for them. We met with only here and there a 

 straggler in Manitoba; but they were more numerous, as we have just 

 seen, farther west. After the middle of July the flights began to trend 

 in the opposite direction, or toward the south, and the data, which we 

 have been at some pains to obtain on the autumn flights (App. 12), 

 show that they were, as usual, pretty constant in the same direction. 

 It is clearly shown that in the more northern parts of the country the 

 northward-bound insects are often driven back and forth, constantly 

 diminishing in numbers, and from their harmlessness and the fact that 

 the northwest breeding-grounds are known to have been measurably 

 free in spring, it is more than probable that the autumn flights over the 

 temporary region were made up of the more robust of the insects that 

 had, earlier in the season, left that region. West of the Eocky Mount- 

 ains, and in restricted sections in Montana, east of them, the flights 

 prevail in other directions. 



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