﻿106 EIGHTH ANNUAL REPORT 



other words, toward what I believe to be the native home of the spe- 

 cies, whence their parents had come in 1S74. That they instinctively 

 sought this direction there can, I think, be no doubt; for while they 

 depend in great part on the wind for propulsion, and without its aid 

 would be unable to migrate to very great distances, I have a large num- 

 ber of reports to show that whenever the wind blew from the north 

 or northwest, the locusts came down and waited a change to a more 

 favorable direction. They begin to rise when the dew has evaporated, 

 and descend again toward evening. A swarm passing over a country 

 yet infested with the mature insects, constantly receives accretions 

 from these, and is, consequently, always more dense in the afternoon 

 than in the forenoon. In rising, the insects generally face the wind, 

 and it is doubtful if they could ascend to any great height without 

 doing so. They are, I believe, good navigators, and know how to take 

 advantage of the diflferent air currents. The rate at which they travel 

 will depend on the force of the wind ; but it is evident from the ob- 

 servations made in Dakota, where their advance was reported by tele- 

 graph, {ante p. 37,) that last Spring they often traveled a hundred 

 miles a day. Their minimum speed, in tolerably calm weather, when 

 the wind is scarcely felt at the surface of the ground cannot be much 

 less than from eight to ten miles an hour. 



The exceptions to the northwest course occurred toward the end 

 of the first week in July, when swarms were seen flying southeast 

 over northeastern Kansas. These could hardly have originated in the 

 adjacent parts of Iowa or Missouri, as the bulk of the insects had by 

 that time left that section ; they were probably detachments of the 

 swarms that left Minnesota about the first of the month and which, as 

 their parents came from the southeast in 1874, instinctively flew in 

 that direction. During July they also flew south from their native 

 hatching grounds in Colorado ; while later in the season, viz. in 

 August, fresh swarms from the northwest and west flew over that 

 State in a southeast direction. 



DESTINATION OF THE DEPARTING SWARMS. 



That the swarms which left the fertile country in which they 

 hatched and are not indigenous — say all the infested region lying^ 

 south of the 44th parallel and east of the 100th meridian — passed by 

 degrees to the northwest and reached into northwest Dakota, Wyom- 

 ing and Montana, the records clearly prove. Whether or not they 

 reached up into British America, I have no means of judging. I be- 

 lieve, however, that few, if any, did. Those which survived long 

 enough to deposit eggs evidently reached the higher and treeless 



