OSTEN SAC KEN ON WESTERN DIPTERA. 299 



sum, scutellum, and pleurae are black ; some few scattered pale colored 

 small hairs are mixed with them. Segments 2-5 of the shining black 

 abdomen have each, on their hind margin, a moderately broad cross- 

 band of whitish pollen. The cross-bands on segments 2-4 are inter- 

 rupted in the described specimen (probably rubbed off ?) ; that of the 

 fifth segment seems to have been interrupted even in the intact speci- 

 men. The hairs on the abdomen and hypopygium are, without excep- 

 tion, black ; a part of the hairs near the lateral margins has the ends of 

 a lighter color. The hairs on the coxae are whitish, those on the hind 

 coxae are mixed with numerous black hairs. The legs are of the same 

 structure as in C. longimanus Loew, especially the front tarsi of the same 

 conspicuous length ; the pile on the femora is prevailingly, but not alto- 

 gether, black ; some whitish hairs on the under side, at the basis of the 

 front femora, and short white hairs on the greater part of the upper 

 side of the hind femora, are especially perceptible ; the front tibiae like- 

 wise have principally black hairs; on the hind tibiae only the under side 

 is beset with long black hairs, while elsewhere short white pile, on the 

 upper side longer white pile, is prevailing. The tarsi are almost exclu- 

 sively beset with black hairs. The bristles on the legs are without ex- 

 ception black (the halteres are wanting). Wings grayish-hyaline, hardly 

 more grayish on the distal half ; the veins normal, brownish black ; the 

 central cross- veins with vestiges of darker shades in their surroundings, 

 which will probably not be visible in fresher specimens. 



"Hob.— Sierra Nevada (H. Edwards)." 



I have three males from Webber Lake, Sierra Nevada (July 22), which 

 seem to belong to this species. The white pile on the face prevails 

 over the black, which is distinct on the under side only, but very scarce 

 on the sides ; a very thin brownish pollen conceals but very little the 

 black, shining thoracic dorsum; a median geminate stripe is hardly 

 visible, but on the side of it a semblance of the figure 5 in gray pollen, 

 with its reverse on the other side, is more distinct; the cross-bands of 

 white pollen on the abdominal segments are all interrupted. Length 

 S.5-9.5 mm . 



I will add the description of the females, taken in the same locality, 

 wbich may belong here. 



Female. — Thorax more densely brownish-pollinose ; the double figure 

 5 on each side of the brown median stripe grayish-pollinose; the white 

 abdominal cross-bands entire, except that on the fifth segment ; sides of 

 the abdomen beset with white pile, alternating with tufts of black pile 

 at the base of the segments ; in some specimens, however, these black 

 tufts are hardly perceptible. The fan-shaped row of hairs in front of the 

 halteres is black here, as it is in the male specimens. Length 10-ll™ m . 

 Four specimens. 



5. Cyrtopogon leucozonus Loew, Bed. Ent. Zeitschr., 1874, 364. 



Female. — Ater, tibiis posticis tamen et metatarso postico rufis, pilis 

 nigris et albis vestitus, abdomine toto albo-piloso, segmentis 2-5 singulis 

 8 H B 



