AMERICAN DIPTERA. 281 



Face, front and occiput grayish pruinose; mystax dense, extending 

 up to antennse, whitish in the center and above, black on the sides and 

 oral margin. Antennas black; third segment longer than the first two 

 taken together, constricted toward base, more swollen distally, style 

 bristle-like, about one-third the length of the third segment. Pile of 

 palpi, front, upper occiput, dorsum, the long pile of the convex scutel- 

 lum and on the pleurae wholly black; that of the basal segments of 

 the antennae largely, lower occiput, proboscis and coxae white. Thor- 

 acic dorsum with a thin brownish bloom, which conceals but very little 

 the black polished ground color; the median geminate stripe is hardly 

 perceptible, but on each side of it a semblance of a figure 5 in gray 

 bloom, with its reverse on the outer side, is more distinct. Pleurae 

 grayish pruinose; scutellum brownish pruinose at base only, polished 

 on the outer margin. Halteres yellowish-white. Abdomen polished 

 black; segments 2-5 each with a moderately broad cross-band of white 

 bloom apparently entire on segments 2-4, but interrupted on segment 

 5; pile of abdomen wholly black except on sides of first segment, where 

 there is often some white pile, longest on sides of segments 1-2, but 

 gradually decreasing in length from thence to tip. Pile of femora is 

 largely, though not altogether, black; some whitish hairs on the 

 under side of the front femora at the base, and short white hairs on 

 the greater part of the hind femora above are especially perceptible; 

 front tibiae chiefly black pilose, but the hind tibiae are clothed on the 

 under side only with black hairs, elsewhere with white pile, which on 

 the upper or posterior side is more proininent; the pile of the tarsi 

 and bristles of legs black. Wings grayish hyaline, hardly more grayish 

 at the distal half; venation normal, the central cross- vein with vestiges 

 of darker shades which will probably not be visible in fresher specimens. 

 9 . — Quite similar to male, but dorsum more densely and more 

 brownish pruinose, the double figure 5 on each side of the brown 

 median stripe grayish pruinose. Abdomen less pilose, the white 

 pruinose cross-bands of segments 2-5 entire, that on segment 5 some- 

 times interrupted; side of all the segments with short fine white pile 

 except at the base, where the pile is black. Osten Sacken says that 

 this black pile appears as "tufts," but I have not seen indications of 

 such. The trichostical pile is black and white mixed. Tarsi with only 

 traces of reddish color; almost black. 



Type. — M. C. Z. Loew's single male type is, as he says, 

 in poor condition, somewhat greased. The three male and 

 five female specimens mentioned by Osten Sacken in " West- 

 ern Diptera," are at the M. C. Z. and in good condition. 



Habitat. — Sierra Nevada (type), Col.; Beulah, N. M. (H. 

 Skinner) ; Yosemite, and Webber Lake, Sierra Nevada (July 

 22, Osten Sacken); Vernon, B. C. (May 14, 22, Miss Ricardo). 



TRANS. AM. ENT. SOC, XXXV. (36) JULY, 1909. 



