316 ERNEST A. BACK. 



on the head and humeral angles of the thorax; the pleurae and coxse 

 likewise very thinly white pruinose. Abdomen polished black, on the 

 tergum almost bare. Mystax and pile of entire body of male, snow- 

 white, of the female white or sometimes pale yellow and, aside from 

 the very short pile of the tergum of the abdomen, very long. In the 

 male, the pile of the venter of the abdominal segments 1-3 is long 

 and forms a large tuft which can readily be seen from above. Legs 

 wholly black; pulvilli pale. Wings purest hyaline, veins pale yellow; 

 venation normal. 



Type. — M. C. Z. The type series consists of four male and 

 five female specimens. 



Habitat. — Neb. (type); Glen, Sioux Co., Neb. (P. R. Jones); 

 Lorrey's Lake (Sept. 7) and Carbon Co. (Am. Museum), Wyo.; 

 Col. (Aug., C. W. Johnson). Prof. R. A. Cooley has sent me 

 specimens from the following places in Montana: Lombard 

 (July 25, elev. 4,000 ft.), Livingston (July 14), East Flathead 

 (July 25, elev. 5,700 ft.), Bozeman (June 25, July 3, elev. 

 4,800 ft.), and Lolo Mount, (July 1). 



In specimens which have been kept a long time under poor 

 conditions, and those which have become greased, the pile is 

 matted or otherwise injured, so that it does not appear very 

 prominent. 



Holopog-oii siiowi n. sp. (PI. XI, fig. 2) . 



9 . — Length 6-8 mf^i. — Black; when viewed from the side, the gray- 

 ish bloom of the anterior portion of the thoracic dorsum and of the 

 pleuras stops short at the transverse and mesopleural sutures respec- 

 tively; legs black, the tibise and tarsi dark reddish. 



Wholly black, including the antennas; the abdomen highly polished; 

 pile of the entire body white, except that on the upper occiput, basal 

 segments of antennae, a few hairs on the upper and lower portions of 

 face and on the posterior portion of dorsum, which are black. Face 

 and front densely brownish-yellow pruinose; the occiput black; the 

 ocellar tubercle with a tuft of white hair. The pruinose spot on each 

 side of the thoracic dorsum, including the humerus and extending in- 

 ward to the median thoracic stripe and backward as far as the trans- 

 verse suture, is gray, with a slight tinge of yellow; the bloom of the 

 pleurae is most dense upon the mesopleurae. When viewed from the 

 side, the bloom of thoracic dorsum and pleuras stops suddenly at the 

 transverse and mesopleurae sutures respectively; the remainder of the 

 pleurae is clothed with a pale bloom, which is nearly or quite as dense 

 on the sternopleurae as on the mesopleurae, but elsewhere very much 

 thinner and hardly perceptible. The broad median thoracic stripe 



