PACKAKD.l THE LOCUST IN COLORADO. 595 



on the fallen trees by tlie side of a brook, while the atlnlts wore fl.vin;? 

 perhaps 1,000 feet overhead. On the extreme summit (elevation 14,llf, 

 Parry's estimate 14,216, feet), the locusts were flying, though not in great 

 abundance, at least 500 feet above the top; some f^U with a thud on tiie 

 rocks and seemed paralyzed or were found benumbed on the snow. I 

 did not notice that they were flying in any determinate direction, but 

 as vast numbers of a green Haltica covered tlie low alpine vegetati(jn, 

 I judge tbat as these had evidently been borne up by currents of wind 

 from the plains below, the locusts had been carried up in a similar 

 manner, especially as they were more abundant on that day at an eleva- 

 tion of 8,000 to 9,000 feet. That, however, even at this latter elevation, 

 the winged locusts had probably come from the plains east of the mount- 

 ains seems evident, as the young born at this altitude had not yet ac- 

 quired their wings. Indeed, it seems to me exceedingly doubtful whether 

 those born above an altitude of 8,000 or 9,000 feet arrive at maturity if 

 they do acquire wings; their flight is only local, from one canon to 

 another. It seems evident that the vast swarms which appear occa- 

 sionally must have been hatched on the plains to the west and northwest, 

 at an altitude of 5,000 to 7,000 feet. 



As regards the inferences to be drawn from my own observations in 

 Colorado, which were made between June 27 and July 19, namely, after 

 the spring brood had taken flight and before the late summer swarms 

 had arrived on the plains, I would state: 



1. That in the caQons and mountains above an elevation of about 

 8,000 feet the young were too few in number and too late in their devel- 

 opment to supply the material for the swarms that visited the plains 

 about Denver in August. 



2. The grasshoppers seen by me sailing in the air between about 0,000 

 and 9,000 feet elevation were probably derived from the April and May 

 broods of the plains about Denver, east of the foot-hills of the Rocky 

 Mountain Range. 



3. The August swarms which spread over the plains about Denver 

 and the country north and south, within a hundred miles or so, origi- 

 nated in Colorado, but probably not the adjacent Territories, and were 

 derived from those bred on the plains about Denver directly east of the 

 mountains, which were borne aloft in June, and then collected in large 

 swarms and migrated back, borne by westerly winds, later in the sea- 

 son, to find suitable places for laying their eggs. It is not improbable 

 that the earliest local swarms, such as devastated the plains of Colorado, 

 bred in the plains about Denver, and gathered for about a mouth in the 

 lower portion of the mountain valleys into the compact and well-organ- 

 ized swarm which, to some extent,, devastated the Colorado Plains. 

 Undoubtedly^ the sexual instinct leads large swarms, bred during favor- 

 able seasons, to migrate in search of broad plains which aflbrd the proper 

 conditions for the deposition of their eggs and the nourishment of their 

 young. But it is evident that the parks and canons of the Rocky JMount- 

 ains of Colorado, all of which lie above an altitude of 7,000 "feet, pre- 

 sent conditions of elevation, climate, extent of territory, and food too 

 unfavorable for the production of the immense swarms which at long 

 intervals devastate the Colorado Plateau and portions of Kansas and 

 adjoining States. It is most probable, however, that the late August 

 and early September broods of locusts noticed by Mr. Byers about 

 Denver may have been born and bred during exceptionally dry seasons 

 in the plains of Wyoming and Montana, and thus appeared in Colorado 

 a month later than those bred east of the mountains. It is doubtful if 

 the young individuals (larvje) which I saw at different elevations up to 



