134 Annals Entomological Society of America [Vol. XII, 



six segments with long white hair parted at the middle and directed 

 outward. Hypop3'gium black with black hair. See Figure 52. 



Female abdominal segments all black above, sides and narrow hind 

 margin of each gray pollinose, oviduct about as long as the last four 

 abdominal segments. Fresh specimens have the body more or less 

 metallic, which accounts for Schaeffer's name. 



Specimens from Montana, Colorado, New Mexico, Arizona 

 and Nevada. 



The. robust form and white-haired scutellum are character- 

 istic for the species. 



Erax cressoni n. sp. 



Male. Total length 14 millimeters. Mystax and beard white, 

 palpi black haired, mane-like row of hairs on the middle of the meso- 

 thoracic dorsum black and composed of numerous short hairs and an 

 occasional long one, space in front of the scutellum with scattered black 

 bristles and short white hairs. Scutellum with numerous short white 

 hairs on the disc and four long dark bristles on the margin; femora 

 black, tibi« and tarsi red; wings hyaline, branching of the third vein 

 far beyond the base of the second posterior cell, anterior branch with 

 scarcely a suggestion of a stump. Abdomen, first segment white 

 haired, second to fifth segments with white hair parted at the middle 

 and directed outward, hair shorter on the fifth segment than on the 

 others, first segment, anterior part of second and a small triangle 

 anteriorly on dorsum of third showing dark from above, otherwise 

 abdominal segments silvery white. Hypopygium dark, pale hairy, 

 superior part notched at apex, part above notch narrow, but of same 

 length as part below. See Figure 50. 



Female. Length 14 millimeters, like the male in most respects; 

 anterior branch of the third vein with a stump about equal in length 

 to the basal section, each abdominal segment with a triangular spot 

 which is not as densely pollinose as the other parts, oviduct shining 

 black, about as long as the last three abdominal segments. 



Type: Male and allotype from Alamogordo, New Mexico, 

 in the collection of the Academy of Natural Sciences of Phila- 

 delphia; other specimens from El Paso, Texas. 



Named for E. T. Cresson, Jr., who sent me the specimens. 



Erax costalis Williston. 



Total length, male and female, 14 to 16 millimeters. Mystax 

 white with some black bristles intermixed, scutellum with abundance 

 of white hair and about four black marginal bristles, wings hyaline, 

 femora black, tibi^ and tarsi mostly dark red. Male, abdomen with 

 segments two, three and four with long white hair parted at the middle 

 and directed outward, first three segments largely black dorsally, 

 apex of three and all of segments four to seven inclusive silvery, hypo- 



