290 ERNEST A. BACK. 



abdominal segment is not interrupted (the thorax of the specimen 

 is greasy) ; the claws are whitish-yellow, with black tips, a very char- 

 acteristic mark of the species." 



Type. — M. C. Z. Four female, and one male specimens. 



Habitat. — Webber Lake, Sierra Co., Cal. (Osten Sacken) ; 

 Mt. Hood, Oregon (Williston) . 



I have the following notes upon the type material. Face, 

 front, occiput, pleurae, scutellum, grayish-white pruinose; pile 

 of face, front and upper occiput fine, black, not dense, nor 

 obscuring the bloom. Beard, pile of pleurae, trichostical pile, 

 and that of the sides of the segments 1 and 2 of abdomen 

 white. Pile of thoracic dorsum short, erect; bristles black; 

 scutellum with long weak bristles only on the posterior mar- 

 gin. Legs black; often tinged with chestnut; coxae white 

 pruinose; femora below with white pile; rest of the pile and 

 bristles black. 



Williston states that a male from Mt. Hood has the second 

 and third abdominal pruinose cross-bands narrowed in the 

 middle, but entire (thus removing the doubt from Osten 

 Sacken's male). I have two females and two males from 

 Cloudcroft, N. M., belonging to the Am. Ent. Soc. which I 

 refer to this species. 



Cyrtopogon positivus, 



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

 "%. — Length 7-8 mm. — Peculiar coloring of the thoracic dorsum; 

 the extreme anterior margin and the posterior beyond the thoracic 

 suture are grayish; the intervening space is of a rich dark brown, the 

 usual stripes coalescing completely; they reach for a very short distance 

 beyond the thoracic suture; the longitudinal dividing line of the 

 median stripe is very feebly marked with a paler bloom (sometimes 

 indistinct) ; front and face rather narrow, clothed with a brownish 

 bloom and dense deep black pile; first segment of abdomen black, with 

 very little white on the sides; posterior margin segments 2-5 marked 

 with white on the sides only, the interruption growing wider on each 

 subsequent segment." 



Type. — M. C. Z. Three male specimens. 



Habitat.— Webber Lake, Sierra Co., Cal. (July 22-24, Osten 

 Sacken); Moscow, Idaho (F. H. Snow); Cloudcroft, N. M. 

 (May 17, 23, 27). 



Beard white. White pile on the first three abdominal seg- 



