158 REPORT UNITED STATES ENTOMOLOGICAL COMMISSION. 



flight was northeast across the Saguache Monntaios to Lake County. 

 Oq the main Arkansas Kiver, in Lake County, they fly east. These 

 flights are more or less local and evidently determined by the variable 

 winds in this mountain region. It seems, however, to be a matter of 

 fact that a large proportion of the locusts which devastate the arable 

 portions of Colorado appear late in July and duriug August, just as 

 the harvest is over, from the northwest and west, and that by the early 

 part of September they reach Texas, and continue to pass across the 

 plains in a general southeast course until early in November. 



Eastern Idaho and Utah. — In considering the migrations of the locusc 

 in the Upper Snake River Valley and in Utah, we should bear in mind 

 that this region is a southern continuation of Central Montana, this being 

 apparently the main source of the locusts which invade Utah. Our 

 observations in Idaho are quite satisfactory, as on the stage road from 

 Franklin to Virginia City we were enabled to gather considerable infor- 

 mation. From various sources it seems well established that the locusts 

 invariably fly south from the region of Virginia City, past Market Lake 

 and Fort Hall into the Bear River and Malade Valleys. At Franklin 

 we were told that the swarms always come from the north. Mr, J. B. 

 Hunter told us that in driving cattle for a distance of about 200 miles 

 south from Virginia City, swarms of locusts kept moving ahead of him, 

 flying either southeast or southwest, but never in a northward course. 

 At Franklin the parents of the young locusts observed by us early in 

 June were said to have come from a region 200 miles north, namely, 

 Central Montana ; they appeared from a point a little east of north in 

 September, 1876. It thus appears that when they are abundant one 

 year in Central Montana, they fly south into ISTorthern Utah, Cache and 

 Malade Valleys and lay their eggs. The young hatching out the suc- 

 ceeding year, or becoming fledged, fly south into the Salt Lake Valley, 

 For example, the locusts which hatched out in Salt Lake Valley were 

 said to be the progeny of those which bred in Malade and Cache Valleys 

 the year previous. 



At Logan City, in the Bear River Valley, and at Smithfield. they were 

 observed to come from the north. At Plain City, Weber County, in 

 1867 they came from the northeast, and departed in forty-eight hours 

 in a southwest direction, which took them over Salt Lake, when by a 

 change of wind many perished in the lake. At Nephi, in Central Utah, 

 and at Saint George, on the southern border of Utah, they arrive usually 

 from the north. For two successive years, according to Mr. Siler, the 

 flights in Southern Utah were to the north ; these were probably return 

 flights, the progeny of those which came the preceding years from the 

 north. 



MIGRATIONS OF THE LOCUSTS IN THE LOWER SNAKE VALLEY. 



The course of the flights in the Lower Snake Valley is mainly, so far as 

 we have been able to learn, in a general westerly direction. We heard 



