THOMAS ON ORTHOPTERA OF DAKOTA AND MONTANA. 487 



meridian ; on the south, the sonth line of Colorado and Utah;^ on the 

 west, the west line of Utah extended north to British America ; the 

 northern line being somewhere in British America — even this area in 

 the northern part being expanded indefinitely east and west. 



Now for the proof. 



While connected with the United States Geological Survey, under 

 Dr. Hayden, for four years, I traveled over a large portion of the area 

 mentioned, traversing it on various lines east and west and north and 

 south, studying somewhat carefully the habits of these destructive 

 locusts. During this time I noticed them in the larva and pupa state, or 

 depositing their eggs, at the following places : — At various points along 

 the east base and in the bordering valleys of the mountains in Wyoming 

 and Colorado, from l^orth Platte, near Fort Laramie, to the Arkansas 

 River ; in Laramie Plains and around Fort Bridger ; from Utah Lake 

 in Utah to Fort Hall in Snake River Valley, Idaho ; in Northwestern 

 Dakota near the Red River of the North, and on both sides of the range 

 in Montana along the valleys of Deer Lodge River, and the branches of 

 the Upper Missouri. I also obtained satisfactory proofs of the same 

 thing occurring in British America north of Dakota, in Middle Park, 

 Colorado, and in the regions west of that point, in Wind River Valley 

 in Wyoming, in Central Montana along the Yellowstone, and in the 

 Green River country west of South Pass. These facts, which are but a 

 small portion of what might now be gathered, will give some idea of the 

 work necessary to be done if we undertake to exterminate these insects 

 by destroying their eggs in their native haunts. 



In order to further illustrate, and belter understand the point now 

 under consideration, I will present some facts in regard to their migra- 

 tions in and from the mountains and northern regions, which, will assist 

 the reader in forming a more correct idea of their habits, and the extent 

 of their operations, — and here be it remembered I confine myself to the 

 single species Caloytenus spretus. I have traced a swarm from the area 

 west of South Pass to their stopping-place and hatching-ground north 

 of Fort Fetterman, from Northeastern Dakota nearly to Lake Winni- 

 peg, and have ascertained that some swarms have extended their migra- 

 tions from some supposed southwest point as far as the north side of 

 this lake. It is also known that, in one instance at least, those which 

 left Colorado moved in the direction of Texas ; those visiting Salt Lake 

 Valley have repeatedly come from the northeast, sometimes doubtless 

 from Cache and Bear River Valleys, and others from the Snake River 

 region 5 while those hatched in Salt Lake regions moved south, in some 

 instances returning with the change of wind. In 1864, those hatched 

 east of the mountains of Northern Wyoming and along the Yellowstone 

 in Montana swept down the east flank of the range upon the fields of 

 Colorado, while a part moved east to Manitoba and Minnesota. In 1867, 

 a swarm from the west side of the range poured into Middle Park, and 

 there deposited their eggs, but those hatched from these failed to scale 



