136 Annals Entomological Society of America [Vol. XII, 



each red, otherwise legs black, wings hyaline, branching of the third 

 vein beyond the base of the second posterior cell, stump very short. 

 Abdomen largely gray pollinose, venter of segment four and five each 

 with a distinct red prominence, narrowed basally and enlarged apically, 

 with the main part of the enlargement directed posteriorly ; sixth segment 

 with a narrow pronounced red tooth-like appendage pointing almost 

 directly downward and acute at apex. Hypopygium red in color, 

 from side view, widest at basal third and gradually narrowed toward 

 apex, where it is almost truncate. 



Type: Male from Santa Rita Mountains, Arizona, 5,000 to 

 8,000 feet, July, (F. H. Snow). In the author's collection. 



The form and color of the hypopygium and ventral abdom- 

 inal prominences easily characterize the male of the species. 



Erax productus n. sp. 



Male. Total length IG millimeters. Body largely white pilose 

 and gray pollinose, palpi black hairy, basal two-thirds of tibiffi red, 

 legs otherwise black, and with black bristles; wings pale yellowish, 

 hyaline, branching of the third vein beyond the base of the second 

 posterior cell, stuinp very short. Abdominal segments four and five 

 ventrally, each with a short blunt prominence, segment six with a large 

 acute prominence directed downward. Hypopygium, from side view, of 

 nearly uniform width, rather long, apically each outer comer prominently 

 produced. 



Female. Of similar size and color as the male; oviduct fully as 

 long as the last three abdominal segments. 



Type: Male and allotype from Flinn Springs, Lakeside, 

 Cal., August 9, 1917. E. G. Holt, collector. Collection of the 

 author. Other specimens from Spring Valley and Poway, 

 August 10 and 14, by the same collector. 



This species is of nearly the same size as tuherculatus, but 

 the ventral abdominal appendages and hypopygium are quite 

 different and easily characterize the male. 



The rufibarbis Group. 



The females of this group differ from all other species by having 

 the last segment of the oviduct divided at the tip. This character is 

 easily seen from dorsal view. The mesothorax and scutellum is unus- 

 ually bristly, the third vein branches beyond the middle of the distance 

 between the base of the second posterior cell and the small cross vein. 

 The male has abdoininal segments six and seven silvery. The oviduct 

 is rather short and rigid and the hypopygium is rather small. Mystax 

 without or with very few black bristles. 



1. Mystax yellow, body and wings dark colored rufibarbis Macquart 



Mystax nearly white, body gray pollinose, wings hyaline. . . .bicaudatus n. sj). 



