22 



The Rocky Mountain Locust. 



when the more typical specimens of the western spretus are com- 

 pared with femur-rubrum as it occurs around St. Louis. That these 

 distinguishing features will lose their value in proportion as 

 abundant material from all parts of the country is examined and 

 compared, I have not the least doubt ; for I have already shown 

 that such is the fact so far as coloration and length of wing is con- 

 cerned, and the meagre material which I have from the East 

 indicates considerable variation and approach in the more important 

 structural characters. 



A THIRD, CLOSELY RELATED SPECIES WHICH IS EASILY 

 COHEOUNDED WITH THE OTHER TWO. 



There is still a third species common in the Mississippi 

 Valley, and particularly along the Atlantic coast, and in 

 the New England States. It is smaller than either the 

 Rocky Mountain or the Red-legged species, but in struc- 

 ture and relative length of wing much more nearly 

 resembles the former than the latter ; in other words, its 

 relative length of wing enables it to fly with almost the 

 same facility as its Rocky Mountain congener. This 

 species I have called the Atlantic Migratory Locust, and 

 it is described below, in comparison with its close allies : 



Caloptenus Atlanis, Riley. — Length to tip of abdomen, 0.70 

 — 0.85 inch ; to tip of closed wings, 0.92 — 1.05 inches. At once 

 distinguished from femur-rubrum by the notched character of the 

 anal abdominal joint in the male and by the shorter, less tapering 

 cerci ; also by the greater relative length of wings which extend, 

 on an average, nearly one-third their length beyond the tip of the 

 abdomen, in the dried specimens ; also by the larger and more dis- 

 tinct spots on the wings— in all which characters it much more 

 closely resembles spretus Xhsmfemw-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 pro- 

 thorax and of the pale line from base of wings to hind tbigh ; also 

 by the anal joint in the 2, tapering more suddenly and by the two 

 lobes formiDg the notch being less marked ; also by the pale marks 

 on the outside of hind thighs being much more distinctly relieved. 

 From both species it is distinguished not only by its smaller size 



