18 The Rocky Mountain Locust. 



tip of the last [ $ ] ventral segment. Posterior lobe of the prono- 

 tum slightly expanding ; median somewhat distinct. Elytra and 

 wings pass the abdomen about one-third their length. The last 

 [ $ ] ventral segment, which is turned up almost vertically, is some- 

 what tapering and is notched at the apex, which distinguishes it 

 from the femur-rubrum ; the notch is small, but is distinct. Pros- 

 ternal spine robust, subcylindrical, transverse. Migratory. 



Color. — Scarcely distinct from the C. femur-rubrum. The occi- 

 put and disk of the pronotum generally reddish-brown; the posterior 

 lobe somewhat paler than the anterior and middle. Spots, as in 

 femur-rubrum, arranged in a line along the middle of the elytra ; 

 these are a little larger and more abundant toward the apex. The 

 head and thorax are sometimes a very dark olive-brown, at others, 

 reddish-brown, and even brownish-yellow, the color deepening 

 with age. The wings are pellucid, nerves dusky toward the apex ; 

 when flying high and against the sun, the wings look like large 

 snow flakes. 



Dimensions. — ? Length [to tip of abdomen], 1 to 1.2 inches; 

 elytra as long as the body ; posterior femora, 0.55 inch; posterior 

 tibiae, 0.5 inch, s Length, 0.85 to 1 inch; elytra, 0.9 to 1.05 inches. 



As with femur-rubrum, the color of spretus is quite variable,, 

 and the dead specimens, from which Mr. Thomas's description is- 

 evidently made, convey a very imperfect idea of the living colors. 

 In the fresh or newly fledged specimens the colors, taken from my 

 notes in the field, are as follows: The more common specimens 

 are yellowish-white beneath; glaucous across the breast and about 

 mouth-parts ; pale bluish-glaucous, often with shades of purple and 

 ferruginous, on the sides of the head and thorax, and the upper 

 front of the face, which is sparsely and shallowly punctate and 

 faintly mottled with fuscous ; olive-brown and rust-red on the 

 occiput and pronotum — the rust-red relieved along the middle in the 

 following characteristic marks : two stripes on occiput, diverging 

 from between the eyes, and a very narrow median line — the brown 

 relieving them in a series of transverse mottlings ; a broad shade on 

 anterior lobes of pronotum, narrowing posteriorly and intersected 

 by black along the median carina, and the three transverse sutures; 



not believe that spretus occurs in Murphysboro, 111., where Mr. Thomas was then 

 residing, and where he quotes Acridium spretis as being quite common; secondly,, 

 because the description in some respects would not apply to spretus as at present 

 defined. I call attention to this discrepancy, because it is upon this (as I believe 

 erroneous) reference, that Mr. Thomas quotes spretus from Illinois ; whereas I 

 agree with Mr. Walsh that (as we understand the species to-day) it is not indige- 

 nous to that State. Where the anal characters of the male are not carefully 

 given, it is impossible to be sure of the species. Mr. Thomas himself now 

 believes that he must have had before him what is defined farther on as Atlanis. 



