1919.] NATURAL SCIENCES OF PHILADELPHIA. 103 



compared with M. m. macchingi, but much variation, often of a 

 confusing character, is found in the large series before us. Pro- 

 gressive elongation and slenderness is evident in material from 

 south-central, south to southern Texas, and in the Trans-Pecos 

 region of the same state, particularly emphasized in specimens from 

 the intermontane section of the Rio Gra*nde valley, to at least as far 

 north as Albuquerque, from the northward of which ' point we 

 have no New Mexico material. From southern Arizona, on the 

 other hand, we find the material unusually robust, in this respect 

 paralleled by AI. neo-mexicana, which has identical tendencies in 

 the same region. 



The variation in general form of the fastigium and of the fas- 

 tigio-facial angle is parallel to that found in other species of the 

 genus, show'ing similar variation in single locality series in both 

 sexes, but, as usual, more pronounced in the male than in the fe- 

 male. The extremes of both sexes in three representative fair- 

 sized series show fastigial (horizontal) angles as follows :cf; Bene- 

 vides, Texas, 63°, 72°; Dallas, Texas, 62°, 84°; Albuquerque, New 

 Mexico, 72°, 75°; 9; Benevides, Texas, 73°, 80°; Dallas, Texas, 

 82°, 88°; Albuquerque, New Mexico, 65°, 82°. 



Non-typical material from northern Texas and Oklahoma 

 shows a distinct shortening and relative broadening of the prono- 

 tum, particularly the disk, when compared with central and south 

 Texas individuals. In typical material the caudal margin of the 

 pronotal disk is more broadly and weakly angulate than in the 

 non-typical material, which averages with more distinct and pro- 

 duced angulation. The more apparent median constriction of 

 the disk of the pronotum, when compared with typical M. m. tnac- 

 clungi, is a feature almost invariably characteristic of M. m. mac- 

 iilipennis, while in non-typical northern Texas and Oklahoma 

 material, particularly of the female sex, the tendency is but faintly 

 or not at all indicated. 



The caudal femora show to an extreme degree the variation in 

 robustness frequent in the genus, and occasionally the disparity 

 in proportion of length to breadth is very marked. 



Synonymy. — Fortunately the species, and more particularly 

 this form, has managed to escape synonyms, which is particularly 

 remarkable when its great variability is known, and when the fact 

 that it was first described from a strongly variant and non-diag- 

 nostic color phase is considered. The general practice has been 

 either to use the name bivittata for the northern race here called 



