1919] Hine: Genus Erax 133 



considers them as belonging to the material which Williston 

 had when he wrote the original description although they are 

 not marked as types. 



Erax jubatus Williston. 



Total length 18 to 23 millimeters. A large, black, robust species, 

 plainly the largest of the group. Mystax composed of numerous long 

 bristly hairs which are mixed white and black in about equal numbers, 

 beard silky white, palpi black haired, hairs and bristles of the thorax 

 largely black, numerous long black bristly hairs on the scutellum and 

 in front of it, although in some specimens white ones are intermixed. 

 Femora black, tibiae and tarsi dark red. Abdomen largely black, 

 narrow posterior margin of the segments gray. Male, abdominal 

 segments six and seven silvery, hypopygium noticeably large. See 

 Figures 3 and 54. Costal margin of the wing prominently expanded 

 and there may be a very short stump on the anterior branch of the third 

 vein. 



Female, usually a distinct stump on the anterior branch of the third 

 vein; oviduct somewhat longer than the last three abdominal segments. 



Forty specimens of both sexes from Northern Mexico, Ari- 

 zona, New Mexico and Colorado. 



A study of the variations exhibited in the specimens at hand 

 suggest strongly that prolificus Osten Sacken, is a synonym of 

 jubatus. The type locality iov jubatus is New Mexico and that 

 of prolificus is Northern Sonora, Mexico. Specimens vary 

 much in some particulars, many have white hairs on the scu- 

 tellum and before it, the bristles of the body are mostly black, 

 but yellow and brownish ones occur, the fifth abdominal seg- 

 ment of the male is almost wholly black, with a rounded black 

 spot, or entirely silvery. 



The large size, generally dark color, and enlarged hypo- 

 pygium suggest the species. However, there is much difference 

 between the largest and smallest specimens. 



Erax subcupreus Schaeffer. 



Total length, male and female, 15 to 20 millimeters. Larger and 

 more robust than costalis. Mystax rather long and dense, composed of 

 black and white bristles and hairs in nearly equal proportion. Mane-like 

 crest of hairs on the middle of the dorsum of the thorax conspicuous, 

 black and reaching well beyond the transverse suture where it merges 

 into a widened area of black and white hairs and bristles which reaches 

 to the scutellum. Scutellum densely white haired and with several 

 black marginal bristles, wings hyaline, femora black, tibiae and tarsi 

 very dark reddish. Male abdomen quite densely haired, first five or 



