32 



" The question then arises : Can meteorologists predict the coming of seasons of mtdue 

 heat and drought 2 and consequently can we predici insect years? that is, the migrations of 

 loatsls and the xmdiie increase of the chinch hug and the army and cotton worm ? I believe 

 that we shall, after the lapse of years, be able to foretell with a good degree of cer- 

 tainty locust invasions, and be able to provide against the losses thus incurred. 



" On the frontier of the Western States, in Colorado, or in the Territories of 

 Wyoming, Montana, and Utah, where the losses from the ravages of the locust cannot 

 easily be made up by importations from contiguous territories, it seems the most practi- 

 cable mode to provide in years of plenty against years of want. We should imitate on 

 a grand scale the usage of the ancient Egyptians under Pharaoh, who lai<i up in time of 

 unusual harvests stores of grain for times of famine. It is said that this has been done 

 on a small scale by the Mormons. If this were done in the far West, in seasons imme- 

 diately preceding insect years, which had been predicted by entomologists in conjunction 

 with the meteorologists, we should be saved the distress, destitution, and even loss of life 

 from starvation, which have resulted from ignorance of the laws regulating the appear- 

 ance of destructive insects, especially the western locust. 



" The Return Migration. — By simultaneous observations for a number of years over 

 the region liable to be visited by migratory hordes of locusts, added to the knowledge we 

 already possess, it will not only be possible to predict the course of certain swarms from 

 their breeding-places, and their probable destination, so that when a swarm starts from 

 Montana or Wyoming, its arrival in Colorado a week or a fortnight later may with some 

 certainty be predicted, and again, its arrival in Kansas and adjoining States be announced 

 with a certain amount of precision, as has already been done by Dr. Riley, but we shall be 

 able to foretell the course taken in the return flight of their progeny in the succeeding year, 

 I will confess that, previous to my visit to Kansas and Colorado, in 187-5, I was sceptical 

 as to Dr. Riley's opinion that there was a general movement in a north-west course of 

 the young of the previous year, broods from Missouri and adjoining regions north-west- 

 ward. The facts and resulting theory have already been stated in full by Dr. Riley and 

 others. It remains to determine the causes of this return migration, this completion of 

 the ' migration-cycle,' as Professor Dawson terms it. It is evident that in this case the 

 desire for food is not the cause, for food is many times more abundant in the Mississippi 

 Valley than on the plains whither they return. The solution of the problem, I think, 

 must be sought in the direction of the prevailing winds during the middle of June, the 

 time they become winged. It may be found after a series of careful meteorological obser- 

 vations, that the prevailing winds at this early season are southerly and south-easterly. 

 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 Ser- 

 vice 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 Wea- 

 ther Signal Bureau for periods of from two to five (usually the latter) years between 

 1871 to 1876, which show that the prevailing winds in June, in Davenport, Dodge City 

 and Keokuk, Iowa ; St. Paiil and Breckenridge, Minnesota ; Yankton and Fort Sully, 

 Dakota ; Omaha, Leavenworth, and Fort Gibson, Indian Territory — all within the locust 

 area — are from the south-east and south. This fact may be sufficient to account for the 

 prevailing course of the return migrations 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 general north-west direction. It is highly probable that they are 

 borne along by these generally south-easterly winds, and pass over on to the plains. The 

 cause is seen, then, to be entirely independent 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 north-west. Should this be so the cause of the mi- 

 grations is probably purely mechanical. Abundant testimony is at hand to show that 

 tliey are wholly at the mercy of the prevailing winds, and that, as a rule, the course of 

 their migrations is quite dependent on the direction of the winds, while the course of 

 the winds depend more or less on the season of the j'ear. We may expect that future 



