124 DIPTERA OP NORTH AMERICA. [PART II. 



joint of the antennae transverse; third in the male rather large, 

 bare ; the apparently bare and distinctly two-jointed arista is in- 

 serted close to the tip of the antenna. Wings broad, the posterior 

 angle rather strongly projecting ; the first longitudinal vein is 

 rather more distant from the margin of the wing than in most of 

 the other genera, and is longer than usual ; the fourth longitudinal 

 vein is inflected forward before the middle of its last segment, 

 thence however it is quite parallel, or almost parallel, with the 

 third longitudinal vein ; the posterior transverse vein is not ap- 

 proximated to the margin of the wing. The first joint of the 

 hind tarsi without bristles. Hypopygium small, imbedded ; its 

 outer appendages are two very small, narrow lamellae directed 

 downwards ; the interior appendages are of rather simple struc- 

 ture and often not distinctly perceptible. 



The name of the genus (from dpyupoj, silver) has reference to 

 the beautiful silvery lustre of most of the species. 



The hitherto known species are distributed over Europe, a part 

 of Asia and North America. I know seven North American 

 species, of which the first has a hairy scutellum and therefore 

 belongs to the relationship of the European Argyra dlaphana. 

 The other six species have no hairs upon the scutellum ; the upper 

 side of the first joint of the antennae is, in some of them, so 

 scarcely provided with hairs that they can easily be mistaken for 

 species of Leucostola. 



Table for the determination of the Species. 



, / Scutellum hairy. 1 albicans Lw. 



*- Scutellum not hairy. 2 



2 f Feet mostly black. 3 



<- Feet entirely or mostly yellow. 4 



f The entire fore tibiae and a part of the four posterior tibiae yellow. 



2 nigripes, nov. sp. 

 ' j All the tibiae entirely and the root of the fore tarsi yellow. 



3 albiventris, nov. sp. 

 . I The whole feet yellow. 5 



I Not the whole feet yellow. G 



f The first joint of the hind tarsi only with the usual very short hairs, 

 j 4 minuta Lw. 



j The first joint of the hind tarsi with longer hairs than usual. 



5 calcitrans Lw. 



g l Tip of the hind femora not black. 6 calceata Lw. 



t Tip of the hind femora black. 7 cylindrica, nov. sp. 



