490 BULLETIN UNITED STATES GEOLOGICAL SUKVEY. 



Colorado, and another detachment into Minnesota, but not reaching the 

 settlements of Nebraska and Kansas. In 1866, we find them spreading 

 over Nebraska and Kansas, and even reaching Missouri and Texas, an 

 invasion which has almost universally been attributed to a direct 

 importation from Colorado. 



Is the opinion correct? Was it not in fact a continuation of that of 

 1864, and, if so, thus showing that these invading hosts have interme- 

 diate stopping-grounds on the great plains, as did the advancing hordes 

 of Asiatic locusts in Europe, and probably even beyond the Bosphorus? 

 In the first place, there is no sufficient proof of any such swarms leaving 

 Colorado in 1866 ; but, on the contrary, the most competent authority in 

 the Territory, Colonel Byers, asserts the opposite in his letter to me, 

 which is published in the Report of Hayden's Geological Survey for 1870. 

 In the second place, as it appears that the great hive of 1864, from 

 which the swarms issued, was Eastern Montana, Western Dakota, and 

 Northeast Wyoming, it is scarcely probable that it would send forth bub 

 two lines, one towards Minnesota and the other towards Colorado, and 

 these at right angles to each other, while the usual direction of air-cur- 

 rents, by which they are carried, is along the diagonal. Again, the 

 advanced guards of those which reached Colorado, and which doubtless 

 came from the nearest hatching-ground, after stopping here a short 

 time, passed off southeast in the direction of the Arkansas Eiver. We 

 hear nothing further of them in 1865 ; but as the remaining portion of the 

 horde of 1864 stopped in Colorado, it is not probable that these proceeded 

 very far, but that they deposited their eggs in Southeast Colorado. The 

 brood of 1865 may have advanced but a short step farther, and then in 



1866 those which entered Texas were t'he first of the advancing column, 

 for it was not until 1867 that the storm fell in its full force upon the 

 interior of that State, and then not until late in the season^October 

 and November. 



Advancing north, we find a corresponding state of affairs. Those 

 "^which hatched in Colorado in 1865 left there in June and passed out 

 •upon the Plains. By turning to the Monthly Agricultural Report of 1868, 

 we find it stated that they were in Arkansas (Montgomery County) in 

 1867. If we suppose those from the section farther north moved in a 

 southeast direction, they would probably have reached the region imme- 

 'diately south of the Black Hills of Dakota ; and it is from this section 

 at is supposed by some that those which visited Iowa came. The time 

 of arrival in Kansas and Nebraska would show a similar rate of pro- 

 gress to the lines already traced, and on this point we have some very 

 strong corroborating testimony. 



Mr. J. A. Allen, of Cambridge, Mass., who was in Western Iowa in 



1867 collecting plants and insects, states that on September 5 he beheld 

 a flight of myriads of grasshoppers coming from the northwest and 

 alighting so thickly as to cover the ground ; that on the 13th he saw 

 another immense flight coming from the same direction. He adds, that 



