26 The Rocky Mountain Locust. 



of the country, will very likely write : Caloptenus femur - 

 rubrum, DeGeer, var. spretus, Thomas, var. Atlanis, Riley; 

 but the broad fact will remain that these three forms — 

 call them races, varieties, species, or what we will — are 

 separable, and that they each have their own peculiar 

 habits and destiny. 



COMPARISONS OF THE THREE ALLIED SPECIES IN THEIR 

 EARLY STAGES. 



Comparisons of the immature stages of these three species show 

 that, when large material is examined, femur -rubrum and Atlanis 

 are more nearly allied than this last and spretus, though, as in the 

 mature insects, they approach each other through exceptional 

 individuals. 



In the first stage, spretus has a decidedly ferocious look, the head 

 being out of all proportion to the rest of the body. The colors are 

 brown, gray and dull white, the general tint being light gray, and 

 the insect presenting a mottled and speckled appearance. The 

 antennae have several joints less than when mature, and are more 

 thick and clavate. The frontal ridge is more prominent and deeply 

 sulcate. The cerci extend beyond the rounded tip of the abdomen. 

 The tarsi show the three joints, but the middle one less distinctly 

 than afterwards. The medio-dorsum from vertex to near the tip of 

 the abdomen, is carinate and pale. Of the dark dots and marks 

 the most conspicuous and persistent (for some specimens are much 

 darker than others) are, one behind the eyes, a subquadrate one on 

 the side of the meta-thorax, a crescent streak on the sides of the 

 swollen end of the hind femora, and two spots on the bulbous base of 

 the hind tibiae. In the second stage the face with very rare excep- 

 tions is pitchy black, the top of the head showing the three charac- 

 teristic rows of transverse black marks on a rust-brown ground, the 

 outer rows curving around the eyes, and the middle one broadest 

 and divided by a narrow medial, pale line ; the rust-brown color 

 continues, with more irregular black marks on the prothorax, nar- 

 rowing toward its middle ; on each side of it the anterior part of 

 the prothorax is black, relieved below by a conspicuous, arched 

 pale line, and this again with a more or less distinct dark lateral 

 mark beneath. The cheeks are mottled with rust-brown and edged 

 behind with yellow; the head beneath, and palpi, except a black 

 rim around tips, are pale yellowish. The other colors are much as 



