THE NEW MEXICO RANGE CATERPILLAR. 



65 



geographically close to the main center of distribution. In the cen- 

 ter of distribution, the Mexican plateau, several species may occur 

 in the same region; but whether they are actually associated or not is 

 not known; in the outlying portions of this area the 

 species occur singly. 



Probably all these species are grass-feeders in the 

 larval state and are derived from a common ancestor 

 with this habit which was originally developed from 

 the Mexican plateau, where prairie conditions prevail. 



DESCRIPTION. 



Below are given the technical descriptions of the egg, 

 larval stages, pupa, and adults: 



THE EGG. 



Egg (fig. 32) broadly oval, upper end slightly the larger. A large 

 saucer-shaped depression on two opposite sides gives a somewhat 

 quadrate appearance when viewed from above. Apex flattened, 

 with a small circular central depression that includes the micropyle. 



The entire egg is covered with a dense, homogeneous coating of 

 opaque, impervious material that is quite adhesive when fresh. By 

 stripping off this outside pellicle the true shell is disclosed, delicate 

 and membranous, finely and irregularly reticulate. 



The egg is filled with a finely granular, dark reddish brown fluid 

 that retains its peculiar color throughout the entire egg period, but 

 disappears gradually as the embryo develops, becoming less notice- 

 able during the later stages of incubation. 



Size, exceedingly variable, with an average measurement of 1.5 by 

 1.8 mm. 



THE LARVAL STAGES. 



Fig. 32.-Egg 

 mass of Hemi- 

 leuca oliiix on 

 weed stem. 

 Enlarged. 

 (Original.) 



Stage I (fig. 33). — Head rounded, shining black, the seta 1 rather 

 coarse, whitish; width about 0.75 mm. Body subcylindrical, uniform dark brown; 

 the spines black, equal, with single long whitish primary seta 1 ; on the abdominal seg- 

 ments tubercle % is at the summitof aspine, ii from the skin without spine, m from a 

 spine, iv and v from a single spine; leg plate with two small seta 1 ; on joint L2 a Bingle 

 forked dorsal spine bearing tubercles i of the two sides, /('from the skin as on the other 



Fig. 33.— The New Mexico range caterpillar: Larva, first stage. Highly magnified. (Original.) 



segments; on joint 13 a single forked dorsal spine posteriorly, single subdorsal an- 

 terior, single lateral, none from the skin. On the mesothorax and motaihorax 

 tubercles ia and ib on a single forked spine, iia and iib on another, m and D on 

 single spines. On the prothorax two forked spines on the anterior margin oi cervical 

 shields and one seta from the skin posteriorly; a forked spine bearing two setse 



