38 
Dimensions. —Female. Length to tip of elytra, 1.15 to 1.43 inch* 
usually about 1.30; length of elytra beyond the tip of the abdomen, 
0.15 to 0.38 inch ; usually 0.22 to 0.27 inch. Male. Length to tip of 
elytra 1.15 to 1.40 inch ; usually 1.20 to 1.30 inch ; length of elytra 
beyond the tip of the abdomen, 0.20 to 0.38 inch ; usually 0.25 to 0.33- 
inch. 
The Lesser Locust — (Caloptenus atlanis)— Riley. 
The species most closely allied to spretus , or the Rocky Mountain, 
locust, is C. atlanis , Riley, or the “Lesser Locust,” which the author de¬ 
scribes as follows : “Length to tip of abdomen, 0.70 to 0.85 inch; to 
tip of the closed wings, 0.92 to 1.05 inches. At once distinguished 
from femur-rubrum by the notched character of the anal abdominal 
joint of the male, and by the shorter, less tapering cerci; also, by the 
greater relative length of the wings, which extend on an average 
nearly one-third their length beyond the tip ot the abdomen in dried 
specimens; also, by the larger and more distinct spots on the wings— 
in all which characters it much more closely resembles spretus than 
femur-rubrum. From spretus , again, it is at once distinguished by the 
smaller size, the more distinct separation of the dark mark running 
from the eyes on the prothorax, and of the pale line from the base 
of the wings to the hind thighs; and also by the anal joint in the 
male tapering more suddenly, and by the two lobes forming the notch 
being less marked. From both species it is distinguished not only by 
its smaller size, but by the deeper, more livid color of the dark parts, 
and the paler yellow of the light parts, the colors thus more strongly 
contrasting. 
“Just as the typical femur-rubrum is at once distinguished from the. 
typical spretus bv the characters indicated, so atlanis , though structur¬ 
ally nearer to spretus , is distinguished from it by a glance at its much 
smaller size, and darker, more marked coloring. The contrast is all 
the greater in the living specimens of spretus that at all approach it 
in these respects.” 
I find the male, as seen in Illinois, varies in length to the tip of the 
elytra as follows: 0.97, 0.95, 0.98, 0.95, 0.96, 0.84, 1.05, 0.93 averag¬ 
ing 0.954. 
The Red-legged Locust —( Caloptenus femur-rubrum) — Deg. 
jj i| . I 
This is our common Red-legged Locust, and has been so often men¬ 
tioned and described in scientific and agricultural publications that I 
will simply refer to the differences between it and two other species 
( spretus and atlanis). 
Female.— As compared with spretus the only very marked difference 
between the females is the shorter wings of this species, yet there are 
other slight differences observable when a large number of specimens 
are compared. The eyes in femur-rubrum are slightly more promi¬ 
nent ; the head, pronotum and sides of the thorax are usually sorne 
shade of olive-brown, varying from pale to almost black ; the blacs; 
