59G REPORT UNITED STATES GEOLOGICAL SURVEY. 



about 9,000 feet ever arrived at maturity; they may winter over and 

 acquire ^vin^^5 in tbe spring, but tbis is improbable. 



In Northern Colorado the grasshoppers may have in part taken wing 

 from the Laramie Plains of Wyoming and the phiteau east of the Black 

 Eills, while the swarms devastating Southern Colorado may have been 

 in i)art indigenous and in part derived from the plains of iSTew Mexico 

 on the south and Utah on the west. 



As I was not able to observe the locust in spring or late in the sum- 

 mer, I am obliged to rely on the statement of others regarding the hab- 

 its of the locust at these periods. The following letters from W. N. 

 Byers, esq., written at my request, give an able summary of the results 

 of his observations and are of value, as the leading jjoints confirm my 

 own impressions. It will be seen that I quite agree with Mr. Byers's 

 view that comparatively fe\t of the swarms originate in the mountiiin 

 cafion, as originally stated by the late Mr. B. D. Walsh (based on the 

 statements of Drs. Pairy and Velie), and reiterated by others: 



Denver, Colo., August 22, 1875. 



Dear Sir: Yonr letter of IGth instant is before rae, and fearinii that if may be mis- 

 laid or overlooked if not answered until " the close ol iLo season," I will endeavor to 

 reply, so far as able to do so, now. 



yijiiR- years ago I answered a similar inquiry from Prof. Cyrus Thomas, ak.i'^f Dr. 

 Haydeii's Survey, and I think it found place in some one of the reports. My option 

 respecting the liatching-tields. Sec, of the grasshopper was then seriously questit ned, 

 but Pr()fcssor Thomas, after another year's observation and si ndy, freely admitted that 

 I was right. I presume yon have seen what I wrote at that time, or if you have not, 

 that yon can readily do so. My opinions have not changed since. I may here say that 

 I tirst made the acquaintance of the destructive grasshopi)er in 1852, about the 1st of 

 August, upon the jdains of Northern Utah and Southern Idaho, at which time they 

 were Hying cast-northeast in swarms that obscured the sun. 



Their lueeding-places may be in any part of this arid portion (the western half) cf 

 the United States. The </?•<«< swarms that attain maturity ?nd migrate are hatched, 

 doubtless, within altitudes ranging from 4,000 to 7,000 feet above sea-level. At 7,000 

 to 8,000 feet they may so far mature as to make short flights and remove to new local- 

 ities not far distant. Above 8,000 feet they seldom, if ever, become able to lly, though 

 I have seen myriads of them hatched at 10,\!00, 11,001), and even up to 12,000 feet above 

 the sea. Probably they did not attain more than one-third of their growth before 

 being destroyed by autumn frosts and snows. 



The most iavorable hatching-grounds are the plains like this east of the mountains, 

 u])on which are situate Denver, Pueblo, Greeley, Cheyenne, Fort Laramie, &c., from 

 4,000 to (i.OOO feet above the sea. Where they settle down to propagate their .species 

 they must have subsistence ; hence there must be fertility and vegetation. As to the 

 latter, they are not very particular, but are sure to take the best there is. Sexual 

 union begins in August and the deposit of eggs soon after, and both continue then 

 until stopped by severe frosty weather, say in October. They choose, hrst, plowed 

 ground ; second, comparatively loose sandy or gravelly land, partially but not thickly 

 covered with grass or other vegetation ; third, the most favorable spots where they 

 may happen to be and from which they are not able to get away. The female, with 

 her nether extremity, perforates a hole in the ground about as deep as the length of 

 her body, and deposits a cluster of eggs that resemble in size and form the eggs of the 

 caterpillar-moth attached to the twig of an apple or cherry tree, except that in the 

 ]>liice of the twig there is a hollow space. They are cemented together by a glutinous 

 substance, which is ooubtless impervious to water. The eggs deposited, the hole above 

 them is soon tilled and leveled by wind or rain. In a warm winter young grasshop- 

 pers are frequently found hatching out at various peiiods. They have been noted here 

 in November, in Febrnary, March, and April, but of course only in limited areas and 

 small nuuibers; and such do no harm, being soon destroyed by cold. The main hatch 

 iug begins about the second week in May, and lasts, say, a month. At higher alti- 

 tudes, from 7,000 to 12,000 ft^et (if eggs happen to have been deposited there, which u 

 rarely the case), the hatching coiatinues from the above dates until the last of August 

 or even into September, owing to the altitude. But from all these latter uo harm ueed 

 ever bo feared. 



The flight of moving swarms is governed mainly by the preva'ling winds, although 

 they seem to be controlled somewhat by choice or laws of their own. A change of 

 wind, or ]iarticnlarly a sudden chill, even slight, brings a flight of them quickly to 

 the ground ; but if the text day is fair and warm, and the wind favorable, they again 



