188 PEOCEEDl^GS 01 TUE SAJWSAL MUSEUM. vol.xx- 



South Saskiitcliewaii to AVyoiiiiiij;, iiiclusivt*, juid in tlie Kockj' Moun- 

 tain region projuT in Colonulo and Ttah. 



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

 mill September, migratory hordes of incr<'dible ninnbers and of both 

 sexes pass from their natural breedin*; «?r(mnds 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 frou) Lake Win- 

 nijieg to or almost to the (inlf of Mexico, rarely ]>assii<;i' fartlier east 

 than lon<»itu«le U3^, and devastating- the countries they reach to an 

 alarming extent, sometimes in places abstdutely destnninji: all standing 

 crops and defoliating fruit trees. 



(3) As they rise for flight from home onlj' 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 tiights to a distance oti 

 at least 500 miles from their jjoint of origin, but there is no <lear evi- 

 •lence to show that (as claimed by the C(unmission) they extend it to 

 dcmble that distance. 



(.">) 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 i)receding year (although on the ground 

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

 their i)revailing <lirection — at least during the earlier part of the sea- 

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

 alight and <*over the ground they are far less harmful than were their 

 invading i)arents. 



(()) 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 \). m., but they are sometimes certainly made at night. 



(7) lielatively sj>eaking. 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 tht invaded soil grow less and less numerous, and, in 

 eftect if not in fact, die out in the course of a very few. i)robably at 

 most two or three, years. 



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

 Commission. It may be worth while to state that in 1S77 I took or 

 noted tiiis insect at the following points; July 11. between Idaho aiid 

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

 Georgetown, Colorado, from 8,500 feet to above timber, mature aii<l 

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

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

 stones on the mountain crests; July 2(K Laramie, Wyoming; July 

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

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

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



