202 REPORT UMTED STATES ENTOMOLOGICAL COMMISSION. 



know that the corresponding species east of the Mississippi Eiver 

 abounds during dry summers following dry and warm springs. 



Given, then, the exceptional years of drought and heat and the great 

 extent of territory, and wo have as the result vast numbers of young 

 hatched out. The year previous having perhaps been warm and dry, 

 the locusts would abound, and more eggs than usual would be laid. 

 These would, with remarkably few exceptions, hatch, and the young 

 soon consume the buffalo grass and other herbage, and move about from 

 one region to another, following often a determinate course, in search of 

 food. In about six or seven weeks they acquire wings. Experience 

 shows that the Western locust as soon as it is fledged rises up high in 

 the air, sometimes a thousand feet or much higher. They have been 

 seen to settle at night on the ground, eat during this time, and toward 

 noon of the next day fill the air again with their glistening wings. As 

 more and more become fledged, the vast swarm exhausts the supply of 

 food, and when the hosts are finally marshalled, new swarms joining 

 perhaps the original one, the whole swarm, possibly hundreds of square 

 miles in extent, begins to fly off, borne by favorable westerly and north- 

 westerly winds, in a generally easterly and southeasterly course. 



Though the winds may vary and counter-currents exist, and storm- 

 gusts from due north, such as often sweep over the plains, and local 

 southerly breezes may retard their flight, the course of the swarms east 

 of the Rocky Mountains is either eastward or southeasterly. The rela- 

 tions between the average direction of the winds and the migrations of 

 the locusts have, however, never been sufficiently studied, either, so far 

 as we are aware, in Europe or in this country. And yet, if we would 

 intelligently study the causes of the excessive increase and migrations 

 of the locust, we must examine the meteorological features of the country, 

 ascertain the periods of drought and undue rain-fall, the average direc- 

 tion of the wind for the different months, in order to learn how far 

 they correspond with the phenomena of insect-life. That there are me- 

 teorological cycles, dry and hot seasons recurring at irregular intervals, 

 while the general average may remain nearly the same century after 

 century, is supported, though it may be vaguely, by observed meteor- 

 ological facts. 



The question then arises, Can meteorologists predict the coming of sea- 

 sons of undue heat and drought, and consequently can we predict locust 

 years f It is probable that we shall, after the lapse of years, be able to 

 foretell with a good degree of certainty locust invasions, and be able to 

 provide against the losses thus incurred. 



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 i)robable destination — so that when swarms start from Montana or 

 Wyoming their arrival in Colorado may with some certainty be pre- 



