Characters of the Species. 



27 



in the mature insects. With each succeeding stage the broad and 

 pale streaks of prothorax intensify, and as soon as the hind wing- 

 pads are turned up over the front pair, viz., in the fourth stage, the 

 pale spot at the base which becomes so conspicuous in the pupa, is 

 visible. The black face after the first molt is quite characteristic, 

 and often endures to the pupa state. 



Atlanis, in the first stage, is distinguished by its deeper, more 

 livid, or rosy, less speckled appearance, and more strongly contrast- 

 ing brighter yellow venter. In the subsequent stages these 

 colorational differences still prevail, and the face is not black as in 

 spretus; the pale spot on the hind wing-pads is less conspicuous in 

 the fourth stage, and the pupa is distinguished not only by its 

 smaller size and different color, but by the narrower, more obsolete 

 black marks of the prothorax and by the wing-pads being consider- 

 ably shorter and smaller, the hind pair livid, with only rarely a 

 touch of black at base, and with the pale spot obsolete. The pale 

 streaks on the outside of the hind thighs are always conspicuous. 

 It presents in fact a marked contrast to the pupa of spretus. 



Femur-rubrum, in the early stages, is distinguished by the gen- 

 erally paler, less livid and greener hue ; by the black being more 

 intense and contrasting more with the pale colors ; by the wing- 

 pads having no pale spot, and by the outer black mark on hind 

 thighs showing no pale streaks. 



Spretus, though palest when mature, has altogether the largest 

 amount of black in the immature stages, and notwithstanding the 

 osculant individuals, one who has great familiarity with these three 

 species in life, can distinguish them with great ease at any time 

 after the first molt, and can even distinguish the cast off skins. 



Further, Atlanis invariably has a pale face — yellow or greenish, 

 speckled with gray-brown ; and just as invariably, the outside of 

 the hind thighs, more mottled, with pale oblique streaks through 

 the black. 



Femur-rubrum has a pale face but less speckled, with no pale 

 streaks through black of bind thighs, and with the upper white 

 mark running from the side of the prothorax much the most con- 

 spicuous on the head behind the eyes. 



A GEEEN VARIETY OF THE EOCKY MOUNTAIN LOCUST. 



In this connection I will also record the occurrence of a 

 variety of spretus, in which all the pale or normally yellow- 



