300 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



postice fascia albo-pollinosa ornatis; alis cinereo-hyalini s. Long. corp. 



4 T 5 2 lin.; long- aL 3 T 7 2 lin« 



(TraDslation.) — "Deep black; hind tibiae red, their extreme base brown, 

 the tip hardly infuscated ; first joint of the hind tarsi dark reddish, brown - 

 ish-black toward the tip. Occiput near the vertex and on the upper 

 part of the posterior orbit beset with black pile ; below, the pile is white 

 or whitish; front with long black pile. The hairs on the first two antennal 

 joints are whitish, (third joint wanting). The dense inystax, which 

 reaches the antennae, is black, with a moderate number of white hairs 

 on the inside of its upper half. Palpi with black pile. The thoracic dor- 

 sum seems to have been clothed near the humeri with whitish-gray, else- 

 where with brownish-gray pollen. (The condition of the specimen for- 

 bids any positive statement.) The hair on the thoracic dorsum is prin- 

 cipally whitish ; from the middle, however, toward the anterior margin, 

 the blackish hairs become gradually more numerous. The usual bristles 

 near the lateral margin and above the root of the wings are black. Nu- 

 merous whitish hairs are mixed with the long black pile on the scutel- 

 lum ; the hairs on the pleur are exclusively whitish. Segments 2-5 of 

 the shining black abdomen each have on their hind margin a moderately 

 broad cross-band of white pollen ; that on segment 5 is interrupted in 

 the described specimen (probably denuded). The hairs on the abdomen 

 are without exception white, longer at the base, shorter and more scarce 

 toward the end, on the last segments erect, in the usual manner. The 

 pile on all the coxae is whitish, without any admixture of black hairs. 

 The hairs on the femora are prevailingly but not exclusively whitish ; 

 those on the front femora toward the tip are mostly black on the upper 

 and the front side ; on the hind femora, most of the black pile is at the 

 end of their posterior side. The hairs on the front and middle tibiae are 

 mostly black ; on the upper side of the middle tibiae, numerous white 

 hairs are mixed with them ; on the hind tibiae, the under side is beset 

 with long black hairs, while the remaining pubescence is white; on the 

 upper side, rather dense and moderately long. The hairs on the tarsi 

 are exclusively black ; the bristles on the legs are also black. Halteres 

 whitish-yellow, with a brown stem; wings grayish-hyaline, hardly 

 more grayish on the distal half; the venation normal ; the veins brown- 

 ish-black ; the central cross- veins show in their immediate surroundings 

 distinct traces of a darker shade, which are probably less distinct in 

 very fresh specimens. 



" Hab.— Sierra Nevada (H. Edwards). 



" Observation.— Cyrt, leucozonus is so very different from C. montanus, 

 especially in the color of the pubescence of the whole thorax, of the ab- 

 domen, and of the femora, that I do not dare to take it for the other sex 

 of that species, although in the structure of the legs and in the position 

 of the bristles on them their agreement is such as usually occurs between 

 the sexes of the same species/' 



I have five female specimens from Webber Lake, Sierra Nevada, July 



