JAMES A. G. REHN 231 



to the eastward showing a marked Great Plains influence in in- 

 stabihty of features and tendency toward D. h. haydenii. South- 

 ward in Mexico it is known to occur as far as Camacho, Zacatecas. 

 This subspecies is new and is here described. 



Derotmema haydenii tnesembrinum^ new subspecies Plate XXVI, figs. 

 1 and 2; plate XXVIII, figs. 1 and 2.) 



This race is more nearly related to D. h. haydenii (see plate 

 XXVI, figs. 3 and 4; plate XXVIII, figs 3, 4, 5 and 6), from 

 which it is chiefly separable in the male sex having the ej^es larger, 

 more prominent and protuberant, more circular in basal outline 

 and deeper in proportion to the infra-ocular portion of the genae, 

 and in the slightly broader pronotum; in the female sex it can be 

 distinguished by the eyes being slightly more prominent and the 

 pronotum distinctly broader, particularly the metazonal portion 

 of the disk. From D. h. rileyanum (see plate XXVIII, figs. 7 

 and 8) the present race differs in the male sex having more promi- 

 nent eyes, which are somewhat more elevated, although not as 

 rounded in basal outline, more prominent fastigio-facial angle 

 when seen in profile, and in the prozonal lobes of the median 

 carina of the pronotum being of the type found in D. h. haydenii; 

 in the female sex differing much as in the male sex, but with 

 features less decidedly indicated, also in the pronotum having 

 the metazona appreciably broader and in general more deplanate 

 on the disk. 



Type. — cT ; Double Windmill," Brewster County, Texas. 

 Elevation, 2725 feet. September 3, 1912. (Rehn and Hebard.) 

 [Hebard Collection, Type no. 490.] 



Description of Type. — Agrees fully with virtual topotypes of D. h. haydenii^ 

 except in the following characters. Eyes more globose, when seen from dor- 

 sum with width across eyes very appreciably greater than width of metazonal 

 disk, in profile more circular and depth and width more nearly subequal, 

 instead of appreciably deeper than wide, as in the typical form of the species ; 

 in cephalic aspect appreciably more protuberant, making width across eyes 

 decidedly greater, instead of but moderately greater, than greatest width 

 across genae. Pronotum with the metazona of disk slightly more transverse. 



Allotype. — 9 ; Marfa, Presidio County, Texas. Elevation, 

 4650 to 4750 feet. September 1, 1912. (Rehn and Hebard.) 

 [Hebard Collection.] 



* From fjLtcrriiu^pLfov, southern. 



'Appearing on the recent government topographic map as "Twin Mills." 



* From Casper, Wyoming. 



TRANS. AM. ENT. SOC, XLV. 



