AMERICAN DIPTERA. 291 



ments tufted and quite long in proportion; it, together with 

 the grayish bloom of the posterior portion of the thorax and 

 scutellum, is one of the principal distinguishing features. 

 Trichostical pile black. Legs wholly black, not abundantly 

 clothed with black and white pile; bristles black. 



I have a male from Moscow, Idaho, which I refer to this 

 species. It is a trifle larger than the type material and is 

 greased, but has the same characteristic white pile of the 

 abdomen. There appears to be a white pruinose spot on the 

 sixth segment; there is a similar spot on a corresponding seg- 

 ment of one of Osten Sacken's co-types which he failed to 

 mention. 



Cyrtopogoii sudator. 



Cyrtopogon sudator Osten Sacken, West. Dipt., 307, 1877. 

 " \, 9. — Length, % 8.5-9 ynm.; 9 8.5-10 nitn. — Front and face dis- 

 tinctly broader than in either evidens, rejectus, nugator or positivus, 

 clothed with a whitish hoary bloom; bloom on the thorax also whitish- 

 gray in most specimens; the brownish stripes are variable, but often 

 feebly marked, although distinct. Often abdominal segments are 

 marked with white on the sides only; in the female, the usual white 

 cross-bands on segments 2-4 are entire, on the fourth interrupted, 

 occasionally subinterrupted on the fourth; in the male, interrupted on 

 all segments." 



Type. — M. C. Z. Two male and eight female specimens. 



Habitat. — Webber Lake, Sierra Co. (July 22-24), and Sum- 

 mit Station, Central Pacific Railroad (July 17), Cal. (Osten 

 Sacken) . 



Pile of face, front, thoracic dorsum, scutellum and before 

 the halteres black; on the occiput, sides of abdominal seg- 

 ments white. Wings hyaline slightly tinged with grayish on 

 the distal half. 



ABERRANT SPECIES. 



Cyrtopogou cerussatu.s. 



Cyrtopogon cerussatus Osten Sacken, West. Dipt., 308, 1877. 



" o ?• — Length 6.5-8 tnni. — Black; thorax whitish pruinose; ab- 

 domen with whitish cross-bands on the anterior margin of segments 

 2-6; the sides of the same segments posteriorly each with a large 

 white spot; wings hyaline; legs black, with white hairs. 



" Face covered with a white hoary bloom; mystax black, more dense 

 immediately above the mouth than higher up; facial gibbosity rather 

 flat, little prominent; antennae black; third segment three times the 



TRANS. AM. ENT. SOC, XXXV. AUGUST, 1909 



