188 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL.XX. 



South Saskatchewan to Wyoming, inclusive, and in the Bocky Moun- 

 tain region proper in Colorado and Utah. 



(2) In certain years, especially in dry seasons, between raid- July and' 

 mid-September, migratory hordes of incredible numbers and of both 

 sexes pass from their natural breeding grounds to the east, southeast, 

 and south, conveyed by the winds (toward which they head) over a 

 greater or less and sometimes a vast extent of country from Lake Win- 

 nipeg to or almost to the Gulf of Mexico, rarely passing farther east 

 tban longitude 93, and devastating the countries they reach to an 

 alarming extent, sometimes in places absolutely destroying all standing 

 crops and defoliating fruit trees. 



(3) As they rise for flight from home only in dry clear weather (when 

 the prevailing winds are from the north or northwest), they do not seri- 

 ously invade the regions (mostly infertile) to the west of their home. 



(4) The invaders extend or may extend their flights to a distance ofi 

 at least 500 miles from their point of origin, but there is no clear evi- 

 dence to show that (as claimed by the Commission) they extend it to 

 double that distance. 



(5) They deposit their eggs throughout the invaded territory, but 

 their descendants therein of the succeeding year not only do not effect 

 a tithe of the damage of the preceding year (although on the ground 

 earlier), but when winged move about in swarms from place to place, 

 their prevailing direction at least during the earlier part of the sea- 

 son being the reverse of that of their parents; but even when they 

 alight and cover the ground they are far less harmful than were their 

 invading parents. 



(6) With few exceptions, movements on the wing are with or nearly 

 with the wind, and are usually made in clear weather between 9 a. m. 

 and 4 p. m., but they are sometimes certainly made at night. 



(7) Eelatively speaking, exceedingly few of the returning swarms 

 ever reach the true home of the species. As a rule, they show signs of 

 enfeeblement and deposit few eggs in the invaded region, so that their 

 descendants on the invaded soil grow less and less numerous, and, in 

 effect if not in fact, die out in the course of a very few, probably at 

 most two or three, years. 



1 can add almost nothing to the facts given by the Entomological 

 Commission. It may be worth while to state that in 1877 I took or 

 noted this insect at the following points: July 11, between Idaho and 

 Georgetown, Colorado, common, both mature and immature; July 12-13, 

 Georgetown, Colorado, from 8,500 feet to above timber, mature and 

 immature; July 16, Argentine Pass, Colorado, 13,000 feet, in abundance, 

 from young just hatched to imagos, and masses of dead imagos under 

 stones on the mountain crests; July 20, Laramie, Wyoming; July 

 21-31, Green River, Wyoming, plenty but not abundant and mostly 

 mature; Alkali Station, north of Green River, Wyoming, 6,000 feet; 

 August 1-4, Salt Lake Valley, mostly mature, very plenty everywhere 



