AMERICAN DIPTERA. 321 



Heteropogon laiitiis. 



Heteropogon lauius Loew, Cent., X, 34, 1872. 



Anisopogon lautus Williston, Tr. Am. Ent. Soc, XI, 16, 1884. 



(^ 9- — Length 9-11.5 mm. — -Black; the thorax brownish-gray pru- 

 inose; the tibiae and tarsi reddish or reddish-brown. In the male the 

 wings are pure hyaline and the front tarsi are densely clothed above 

 with white pile. In the female the wings are pure hyaline except the 

 extreme base as far as the humeral veinlet, which is black; the trans- 

 verse veins, and the unions of the veins, are likewise narrowly margined 

 with black. 



(^. — Black; the tibiae and tarsi reddish, the apex of the former and 

 the several segments of the latter toward the apex a little more deeply 

 tinged. Head covered with a dense grayish-white bloom, opaque; 

 the pile white and bristles whitish; but the bristles of the mystax 

 immediately above the oral margin, all the pile of the palpi, and most 

 of that of the antennse, and indeed the stout bristle which is situated 

 just above the second segment of the antennee — -all black. The whole 

 thorax is obscured by a brownish- gray bloom; the color of the pleurae 

 and of the humeral angles verging much toward a whitish color, that 

 of the rest of the dorsum and of the scutellum much toward brownish- 

 gray. All the pile of the thorax white, bristles black; on the posterior 

 margin of the dorsum and on the margin of the scutellum, whitish. 

 The first six segments of the abdomen black, polished, with very short 

 pile, the posterior margin and the posterior angles of each segment 

 covered with a grayish- white bloom and with very short pale pile; 

 the last two segments, and the small hypopygium reddish; toward 

 the base, the sides of the abdominal segments are covered with long, 

 white pile. Venter grayish, clothed with long, white pile. Femora 

 above almost wholly covered with short black pile, the rest of the 

 pile white, much longer toward the base of the femora; bristles of the 

 femora mostly black, a few whitish. The tibiae covered with white 

 pile and armed with black and white bristles; the front tarsi above 

 densely clothed with pure white pile, the middle and hind tarsi with 

 white hair and black bristles. The middle tibiae are not adorned with 

 the brush of hair and bristles, as it is in some of the other species. 

 Halteres yellowish. Wings wholly purest hyaline, the lower part of 

 the base as far as the axillary veinlet somewhat grayish. 



Like the male, but the bloom of the front, face, dorsum and scutel- 

 lum verges into deep brown; the marginal bristles of the scutellum 

 are black; the abdomen alnaost wholly black, more rarely is absolutely 

 reddish toward the apex; the posterior margins of the several segments 

 scarcely showing traces of a grayish bloom and of pale pile; the front 

 tarsi above are adorned with no dense pure white pile, the lowermost 

 part of the base of the hyaline wings as far as the humeral veinlet, is 

 black, and the transverse veins and junctions of the veins are narrowly 

 shadowed with blackish. 



TRANS. AM. ENT. SOC., XXXV. (41) AUGUST, 1909 



