AMERICAN DIPTERA. 273 



sparsely clothed with yellowish-fulvous erect pile, not concealing at 

 all the ground color, and not forming the fringes of fur so conspicuous 

 in the male; segments 5-7 are almost glabrous, some very scarce, short 

 pile only being perceptible. The thorax is more densely pruinose than 

 in the male; the grayish bloom forms a V-shaped figure posteriorly, 

 the apex of which rests on the scutellum, the ends branch off on each 

 side along the thoracic suture; the geminate stripe is longitudinally 

 divided by a more yellowish line; the usual brownish shadows in the 

 humeral region." 



Type.—M. C. Z. A single male and female. 



Habitat. — Webber Lake, Sierra Nevada, Cal. (Osten Sacken, 

 July 22, 1876). 



The male is easily recognized from all other species by the 

 white tuft of pile on the posterior lateral margins of the first 

 abdominal segment, and the larger tufts of yellow pile on seg- 

 ments 2-4 which are very distinct and unique when viewed 

 from above. The short pile on the terminal segments which 

 forms a brush is another characteristic which goes to make 

 this one of the prettiest Cyrtopogons. The female has a sim- 

 ilar red third antennal segment, but the tufts of pile on the 

 abdomen are reduced in amount so that they are not at all 

 prominent; in fact, cannot really be called tufts in the sense 

 that they are in the male. Pruinose bands, similar to those 

 in the female, are found in the male, but are not conspicuous 

 because of the tufts of yellow pile. In the female the pruinose 

 bands are most prominent ; in the male, the tufts. 



Cyrtopogon princeps. 



Cyrtopogon princeps Osten Sacken, West. Dipt., 302, 1877. 

 " % . — Length 10.5 mm.— Front tarsi remarkably long, once and 

 three-quarters the length of the tibiae; their whole upper side beset 

 with a dense fringe of silvery pile; hind femora, tibiae and tarsi on the 

 upper side with a similar, but broader, covering of silvery pile. Face 

 and front with a brownish-yellow bloom; mystax pale yellow, black 

 only above the mouth and on the lower part of the face; lower part of 

 the occiput with white, upper part and vertex with black pile; third 

 antennal segment red, rather long and slender, the style black. Thorax 

 black, somewhat polished posteriorly, and somewhat brownish-pruin- 

 ose, especially about the humeri; scutellum black; thoracic pile black. 

 Abdomen black, polished, with black pile; segments 2-6 with a yellow- 

 ish-gray bloom on the hind margins; on the second segment, this 

 pollen is visible on the sides only; on the third and fourth, it forms an 



TRANS. AM. ENT. SOC, XXXV. (35) JULY, 1909. 



