196 Proceedings of the Biological Society of Washington. 



Chilosia pallipes Loew. 



This species was described (Cent. IV, 70, 1861) from females collected 

 in the District of Columbia. The male has never been authentically re- 

 corded from this region. The writer believes that males from the Eastern 

 States, which have usually been called C. tristis, are in reality pallipes, 

 as the records and material invariably show only males for tristis and 

 females for pallipes. The difference between the sexes is considerable but 

 the same dimorphism occurs in the sexes of true tristis, undoubtedly cor- 

 rectly associated, and described from the Red River of the North. A 

 description of local males, which are undoubtedly pallipes, is here given : 



Pile on ocellar triangle, dull rufous and with a few black hairs, on the 

 frontal triangle black. Antennae small, reddish yellow ; arista blackish, 

 minutely pubescent. Face shining black, the epistoma not at all pro- 

 duced. Mesonotum shining metallic greenish black; humeri yellow 

 tinged, with white pollen; the pile rather long, dull yellowish brown; 

 lateral margins of mesonotum with long and short black bristly hairs; 

 pleurae with whitish and luteous pile. Dorsum of scutellum with yellow- 

 ish brown pile, the margin with long, slender, black bristles and down- 

 wardly directed long white pile. Legs mostly yellow; front and middle 

 femora and hind tibiae with dark median bands, the hind femora black 

 with yellow base and apex; tarsi yellow, the last joint blackish; first 

 joint of hind tarsi exteriorly blackish, lighter at base and apex. Abdo- 

 men rather slender, brightly metallic bronzy black, the second segment 

 opaque black except at the exterior angles, the third opaque black on the 

 posterior half; pile on fir.st segment and lateral margins of second white, 

 rufous yellow on posterior margin of second and disk of third and fourth. 

 Wings hyaline, longer and narrower than in the female, the last section 

 of the fourth vein consequently longer than in that sex. 



Length 9 mm.; wing 8.25 mm. 



The male of tristis differs in having the face, the epistoma especially, 

 more developed; the pile on the dorsum of the thorax mostly black; legs 

 black, but the apices of femora, the bases and extreme apices of tibiae, 

 as well as the first joint of the middle tarsi, yellowish ; the third abdom- 

 inal segment more extensively opaque black, only the anterior angles 

 shining aeneous. 



Chilosia similis new species. 



Eyes bare; scutellum with marginal bristles; arista short pubescent; 

 abdomen of male in part opaque, the rest shining metallic bronzy black. 



Male : Ocellar and frontal triangles shining black and with black pile. 

 Antennae small, the first two joints shining brownish black, the third 

 ferruginous; arista about two and a half times as long as antenna, black 

 and with rather dense pubescence, most abundant basally. Face shining 

 black, eye margins with very fine, silvery pile; tubercle large, projecting 

 a little beyond antennal prominence. Thorax shining black ; mesonotum 

 with short, rather stiflT, black pile; post-alar calli with black bristles. 



