OSTEN SACKEN ON WESTERN DIPTERA. 301 



22, and Yosemite Yalley, June 8, which agree with this description, 

 with the single exception that on the face there is more than a " moder- 

 ate number" of white hairs. The upper part of the mystax maybe called 

 white, with a few rare black hairs on the sides. I have no male to match 

 these females. 



G. leucozonus and montanus seem to belong to a group of closely re- 

 sembling species. I have several specimens, among them a male from 

 Salt Lake, Utah, which closely resembles the specimens which I have 

 identified with Dr. Loew's descriptions, but cannot possibly be consid- 

 ered as the same species. I am not absolutely certain of having identi- 

 fied those two species correctly ; nor am I very confident that the speci- 

 mens which I described as the female of montanus really belong there. 

 In order to render my possible error harmless, I have purposely repro- 

 duced Dr. Loew's descriptions, and abstained from describing any species 

 of my own belonging to this group. 



6. Cyrtopogon aurifex n. sp., $9. 



Male. — Abdomen narrow, tapering, black, shining, with some bluish 

 reflections on the first segment and very distinct purplish reflections to- 

 ward the tip before the hypopygium ; first segment on the sides with 

 tufts of black pile anteriorly and white pile posteriorly ; the hind part 

 of the second and the greatest part of the third and fourth segments 

 are occupied each by a conspicuous broad fringe of long, erect, yellow- 

 ish-fulvous fur, with narrow bare spaces between these fringes. The 

 three following segments are covered with short, dense, erect, deep black 

 hairs, forming a brush, especially conspicuous on the sides, and longer 

 posteriorly before the hypopygium ; the purplish, black, shining ground- 

 color is almost covered up by this pile ; hypopygium black, shining, 

 with but little pile. Face and front with brownish-gray pollen ; face 

 with whitish pile above and black pile below ; occiput with white pile 

 below and black pile above and on the vertex ; third antennal joint red? 

 the style black. Thorax black, brownish-pollinose, especially about the 

 humeri ; a brown geminate stripe, with a paler, grayish-yellow dividing- 

 line in the middle. Femora black; front tibiae red at base, black on 

 their distal half; the other tibiae red, broadly black at tip ; tarsi black, 

 the base of the first joint and the extreme root of the following joints 

 red ; three first joints of the front tarsi with some white pile on the 

 upper side. Wings brownish-hyaline; fourth posterior cell hardly 

 coarctate at all. Length 8.2 mm . 



Female.r—Legs like those of the male; only the red on the tarsi occu- 

 pies more space and the front tarsi have no silvery pile ; the hairs on 

 the face are more scarce and whitish ; the abdomen comparatively nar- 

 row, shining, black; segments 2-5 each with a moderately broad cross- 

 band of yellowish- white pollen near the posterior margin; segments 2-4 

 are sparsely clothed with yellowish-fulvous erect pile, not concealing at 

 all the ground-color, and not forming the fringes of fur so conspicuous 

 in the male ; segments 5-7 are almost glabrous, some very scarce, short 



