284 GEOLOGICAL SURVEY OF THE TERRITORIES. 



leaving Fort Laramie that the ground seemed alive with them; 

 and in walking a little moving cloud preceded our footsteps." They 

 had probably ceased their flight, and were preparing to deposit their 

 eggs. By reference to my present report on the agriculture of this sec- 

 tion it will be seen that here there appears to be an almost constant 

 current of air sweeping down the Platte Valley from »the west. When 

 we reached South Pass City I learned from Major Baldwin that about 

 the first of the month (August) a large swarm had crossed over the 

 pass from the west, moving eastward, and that they had not gone to 

 Wind Eiver Valley. I am satisfied that they did not go upon the Lar- 

 amie Plains, as I visited that section twice during the season, j^or did 

 we meet with any swarms during our passage up the Sweetwater ; we 

 may, therefore, reasonably infer that those we saw on the North Platte 

 were the same that crossed the mountains at South Pass. From whe*nce 

 did they come ? As we heard nothing of them during our passage down 

 Big Sandy along the stage road, I infer that they must have come from 

 the northwest; but what distance I have no means of ascertaining. As 

 heretofore stated, they have been very destructive in Utah for the past 

 three years, not only injuring very materially the growing crops, but 

 eating the leaves from the fruit trees to such an extent as to injure the 

 fruit. From Dr. A. T. McDonald, of Provo -City, I learned the follow- 

 ing particulars in regard to the incursions of this insect into the Terri- 

 tory. That the prevailing cold and winter storms are from the north- 

 west, but that the grasshoppers seldom come from that direction. On 

 the contrary, they generally came from the northeast through the 

 canons, being brought in by the local currents which sweep through 

 these mountain openings, and that they generally pass off in a south- 

 west direction, though the swarms that come in often remain and de- 

 posit their eggs, from which another brood arises in the spring. Some- 

 times, after a swarm has departed to the southwest, the wind changes, 

 and they are driven back to be swallowed up in the lakes, or perish in 

 the valley. The time of coming varies from the middle of May to the 

 middle of August. The eggs that are deposited here usually hatch out 

 in April and May. The growing crops receive their greatest injury 

 from the young, which are hatched in the valley. The usual method of 

 fighting these young gormands is to drive them into the irrigating 

 ditches, where they are drowned in the water. When they are a little 

 older they are often checked by scattering straw along the edge of the 

 ditches, and driving them into it early in the morning, and then firing 

 it ; those which are not destroyed by the fire being caught in the water 

 of the ditch and drowned. But these methods of combating them are 

 practicable only when they are in the larvas and pupa states. 



Dr. McDonald says that in Utah, at least, the females deposit their 

 eggs in the ground in sacks — a fact heretofore noticed and published — 

 on the gravelly elevated plateaus, or foot-hills. And from my observa- 

 tions this season I am inclined to agree with him in the opinion that 

 these elevated table lands, which are composed of coarse sand ' and 

 gravel, and but slightly covered with vegetation, are the principal hatch- 

 ing grounds of the migratory swarms. The local broods are to be found 

 all over the Rocky Mountain region, from Baton Mountains as far north 

 as I have been, and as far west, at least, as Salt Lake Valley. These 

 are found hatching out in the grassy valleys and broad plains of the 

 lower lands, and up the mountain canons almost to the snow limits. 

 And these broods appear to have little or no connection with the mi- 

 grating broods ; but the solution of these questions will require more 

 extended observations by those who can distinguish the species. 



