124 
30. THE LESSER LOCUST —(Caloptenus atlantis). Riley. 
The species most closely allied to spretus , or the Rocky Mountain 
locust, is C. atlantis , Riley, or the “Lesser Locust,” which the author 
describes 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 of 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 p^rts, the colors thus more strongly 
contrasting. 
“Just as the typical femur-rubrum is at once distinguished from the 
typical spretus by the characters indicated, so atlantis , though structur¬ 
ally nearer to the 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 ap¬ 
proach 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, .095, 0.98, 0.95, 0.96, 0.34, 1.05, 0.93—averag¬ 
ing 0.954* 
31. THE RED-LEGGED LOCUST— {Caloptenus femur-rubrum )—Deg. 
Fig. 22. 
Caloptenus femur-rubrum. 
This is our common Red-legged Lo¬ 
cust, and has been so often mentioned 
and described in scientific and agricul¬ 
tural publications that I will simply 
refer to the differences between it and 
two other species ( spretus and atlantis). 
Female. —As compared with spretus 
the only very marked difference between 
the females is the shorter wings of this 
