118 Annals Entomological Society of America [Vol. XII, 



Erax subpilosus Shaeffer. 



Male. Length 22 millimeters. Head grayish-white pollinose, 

 beard and mystax white, occipito-orbital JDristles white. Thorax 

 black, faintly grayish-brown pollinose, mid-dorsal stripe faint; dorsum 

 sparsely covered with short, black hairs, which are longer apically. 

 Scutellum with black hairs and bristles, some of which are white apically. 

 Pleurae faintly pollinose, covered not densely with moderate long white 

 hairs. Abdomen black, first to third segments with black hairs, longer 

 at sides, fourth segment with long white hairs intermixed with black 

 hairs, which are directed outwardly; fifth segment white pollinose and 

 with shorter white hairs, sixth and seventh segments densely white polli- 

 nose; apical margins of segments two to five grayish pollinose. Venter 

 grayish-white pollinose, covered with long, white hairs. Hypopygium 

 black, clothed with shorter white hairs. Wings pure hyaline. Legs 

 entirely black, clothed with shorter and longer white hairs. Furcation 

 of the third vein almost directly opposite the base of the second posterior 

 cell, stump rather short. 



Female. Total length 22 to 27 millimeters. Colored much as in 

 the male, abdomen black, narrowly gray pollinose on the sides and 

 posterior margin of each segment, hair of the abdomen largely white, 

 but some black, especially on the dorsum. Oviduct rather long, 

 longer than the last three abdominal segments. 



Type: Male, in the Brooklyn Museum of Arts and Sciences, 

 is labeled Beaver Creek Hills, Beaver County, Utah. Other 

 specimens at hand from Reno, Nevada, New Mexico and Cal- 

 ifornia. The California specimens are at the Museum of 

 Comparative Zoology at Cambridge, Mass., and are from the 

 collections of Loew and Osten Sacken. Loew gave the manu- 

 script name lencotrichus to the species. 



The predominance of pure white bristles of the legs is a 

 distinctive character and easily separates it from most related 

 forms. The bristles of the feet especially practically all are 

 white. 



Williston's aridus is much like subpilosus in general appear- 

 ance but the latter has a much longer oviduct. The color of 

 the vestiture of the abdomen is more or less variable in sub- 

 pilosus. 



