20 



The Rocky Mountain Locust. 



are the following characteristic black marks : an annulus near tips 

 of palpi, the inner borders of the mandibles, a spot at the upper 

 outer corner of clypeus, a spot running narrowly around hind border 

 of eyes and then from about the middle of the eye, broadening to 

 thorax; abroad patch on the upper side of anterior half of pro- 

 thorax, zig-zag beneath, and enclosing two pale subquadrate spots, 

 the upper anterior one across the second suture, the lower one 

 between the second and third sutures ; finally, more or less distinct 

 lines along and around the meso- and meta-thoracic sutures. 



There is also a conspicuous pale yellow mark bordering supe- 

 riorly the black stripe behind the eyes, the black of prothorax 

 inferiorly, at outer base of front wings, from this to base of hind 

 thighs and around bases of both middle and hind thighs. 



In the dead specimens all these colors become more dingy and yellow . 

 Palpi and front legs in some specimens tinged with red or blue ; 

 the hind tibiae sometimes yellowish instead of red, especially in the 

 middle ; at other times bluish. 



Larva. — When newly hatched, the larva is of a uniform pale gray 

 without distinctive marks. It soon, however, becomes mottled with 

 the characteristic marks. After the first molt the hind thighs are 

 conspicuously marked on the upper outside with a longitudinal 

 black line ; the thorax is dark with the median dorsal carina and 

 two distinct lateral stripes pale yellow, the black extending on the 

 head behind the eyes. The sides of the thorax then become more 

 3'ellow with each molt, the black on the hind thighs less pro- 

 nounced, and the face almost always black. The occiput and ab- 

 domen above are mottled with brown, the former marked with a 

 fine median, and two broader anteriorly converging pale lines, the 

 latter with two rather broken lateral lines of the same color. 



Pupa.— The pupa is characterized by its paler, more yellow 

 color, bringing more strongly into relief the black on the upper part 

 of the thorax and behind the eyes ; by the spotted nature of the 

 face, especially along the ridges, the black being less persistent ; 

 by the isolation of the black subdorsal mark on the two anterior 

 lobes of the prothorax, and by the large size of the wing-pads, 

 which are now dark, with a distinct pale discal spot, and pale veins 

 and borders. The hind shanks incline to bluish rather than red as in 

 the mature insect. The ground-color in the immature states varies 

 from pale yellow to orange-brown and even black, and from pale 

 yellow to pure green, as in the variety viridis. In many of the 



