1877. ] The Destructive Locust of the West. 27 
It may be found after a series of careful meteorological obser- 
vations, that the prevailing winds at this early season are south- 
erly and southeasterly. It has been shown by meteorologists, 
as I learn from Prof. C. Abbe, that during May and June the 
winds blow inwards towards the heart of the continent from the 
Atlantic Ocean and Gulf of Mexico. On application to Gen. 
A. J. Myer, Chief of the Signal Service of the United States 
Army, for the meteorological data necessary to confirm this hy- 
pothesis, I promptly received a full summary of data observed by 
the officers of the Weather Signal Bureau, for periods of from 
two to five (usually the latter) years between 1871 and 1876, 
which show that the prevailing winds in June, in Davenport, 
Dodge City, and Keokuk, Iowa; Saint Paul and Breckenridge, 
Minnesota ; Yankton and Fort Sully, Dakota; Omaha, Leaven- 
worth, and Fort Gibson, Indian Territory, — all within the locust 
area, — are from the southeast and south. This fact may be suf- 
ficient to account for the prevailing course of the return migra- 
tions of the locust from the eastern limits of the locust area. 
Let us therefore grant this setting-in of southerly and easterly 
winds, which may last until the locusts are winged. When they 
rise on the wing into the air they are known to move in a gen- 
eral northwest direction. It is highly probable that they are 
borne along by these generally southeasterly winds, and pass over 
on to the plains. The cause is seen, then, to be entirely inde- 
pendent of subsistence ; possibly the reproductive instinct causes 
them to become uneasy, restless, to assemble high in the air and 
seek the dry, hot, elevated plateau of the northwest. Should 
this be so the cause of their migrations is probably purely me- 
chanical. Abundant testimony is at hand to show that they are 
wholly at the mercy of the prevailing winds, and that as a rule 
the course of their migrations is quite dependent on the direc- 
tion of the winds, while the course of the winds depend more or 
less on the season of the year. We may expect that future re- 
search over sufficient territory will show that the June migrations, 
from the eastern limits of the locust area, will be towards the 
northwest, and the July, August, and early September migra- 
tions, from the Rocky Mountain plateau, will be in a general 
easterly and southeasterly direction. 
It is not only of great scientific interest, but of high panai 
importance, to collect all facts bearing on the return migrations, 
in order to know where the locusts go in their return migrations 
the second year, as we only know that they do fly a certain dis- : <a 
