213 



phid Hy common in these sand regions, resembles a wasp. A 

 marked case of imitation was that of Cht'loniis fexaiuis, flitting 

 in sparse low vegetation in company with an undescribed 

 Sr/iizocenis, and with difficulty distinguishable from it while in 

 action. 



The non-sympathetic colors of the Acrid iida, such as those 

 of the hind wings and hind tibia?, are of unusual interest, es- 

 pecially as they seem to be subject to alteration — to a varying 

 degree in different species but always in the same direction — 

 as the effect of certain climatic intiuences, apparently that of 

 the degree of humidity, or of humidity and temperature com- 

 bined. 



The bright colors of the hind wings, especially noticeable 

 in the (Edipodina', are curiously at variance with the modest 

 protective tints of the insect at rest. Vosseler suggests that 

 these rainbow hues, which rival in brightness even those of the 

 Lcpidupftrd, con.stitute a "contrast-mimicry."' While the pur- 

 suer is dazzled by the flashing colors, the wings are suddenly 

 closed, and the insect settles quietly to the ground, all track of 

 it being lost in a monotony of color. The genus Catui-ald, among 

 the Lcjiiddpfcrii, is apparently an exactly parallel case. These 

 depend for protection on the close resemblance of the fore 

 wings to the bark of the trees on which they rest. It would 

 seem, however, from the data which follow, that any explana- 

 tion of the origin of the hind-wing colors of Orf/iojjfcra should 

 apply to those of the hind tibiif also. 



Bruner ('93) has pointed out that red-winged specie.s — and 

 he might have also .said individuals — of grasshoppers are most 

 common in humid regions, and yellow-winged ones in more or 

 less arid regions; that in mountainous regions '"just between 

 the dry and wet conditions" blue-winged forms occur: and that 

 from the Atlantic coa.st to the eastern edge of the Great Plains 

 red or orange is the characteristic color, while on the plains 

 and in other arid districts west and southwest these give way 

 almost entirely to yellow. 



In Illinois the hind wings of JJijijjiscas hilicrciilatna and 11. 

 jtlioemcopferiis are red, rarely yellow. Those of our common 



