﻿OF THE STATE ENTOMOLOGIST. 77 



they rise and fly from day to day they concentrate and condense, 

 since in passing over a given area during the hotter parts of the day 

 new accessions are constantly being made to the flying hosts which, 

 with serried ranks, descend in the afternoon. Thus, in returning, the 

 swarms were thicker and more destructive in places than they were 

 in leaving. Yet it is evident that the column which thus came back 

 to Minnesota and passed to the south and southwest was more strag- 

 gling than in 1874, and that by the middle of the month it had spent 

 its force and left eggs throughout most of the country traversed. Had 

 the invasion consisted of these only, the damage would have been but 

 slight, and the insects would hardly have reached into Kansas. Their 

 eggs, laid in August, were far more liable to injury and to premature 

 hatching than those laid later. But it is clear that fresh swarms that 

 hatched in Dakato, and further northwest, followed on the heels of 

 the Minnesota swarms, passing over much of the same country to the 

 east and southward into Colorado, and eventually overruning the- 

 larger part of Nebraska and Kansas, the Western half of Iowa and 

 some of the Western counties in Missouri, and reaching into Indian 

 Territory, Texas and parts of Arkansas. 



The extent of the region invaded will appear by referring to the 

 map (Fig. 16). Coming generally later than in 1S74, they did less 

 damage, and the farmers were in so much better condition to with- 

 stand injury, that it was 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 to that of 1874, for the large extent of 

 country supplied with eggs. Another fact is notable, viz: that the 

 very parts of Minnesota in which eggs were laid in 1875, and the por- 

 tions of Missouri and Kansas in which they were most thickly laid in 

 1874, escaped in 1876. I cannot believe, however, that this is any- 

 thing more than coincidence. 



DESTINATION OF THE DEPARTING SWARMS OF 1875. 



In considering this subject a year ago, I expressed the belief — 

 founded on observation and the records as far as made — that the 

 swarms which left the country south of the 44th parallel and the 100th 

 meridian passed to the N. W., reaching into N. W. Dakota, Wyoming 

 and Montana. I was unable at the time to state whether or not they 

 reached up into British America, and from the large per centage of 

 the departing insects that were diseased and that dropped on the 

 way, I was led to the following conclusions : 



We may very justly conclude that a laro^e proportion of the insects which departed 

 from the country invaded in 187J, perished on their way toward the native habitat of 

 the species, and that those which did not perish reached the Rocky Mountain reo^ion of 

 the Northwest whence their parents had come the previous year. They struggled back 



