1925] New Species of North American Dolichopodidce 187 
but to me it seems best, for the present at least to follow Dr. 
Lundbeck and use the name Gymnopternus as a subgenus. 
Most of our species are easily separated, especially in the 
male, the male hypopygial lamellae of the Hercostomus being 
large and formed about as in the genus Dolichopus; while those 
of the forms coming under Gymnopternus are small and more 
or less crescent shaped; in almost all the species of Hercos- 
tomus , as thus separated, the last section of fourth vein is bent 
or it is convergent with third vein in both male and female; 
while in the subgenus Gymnopternus the third and fourth veins 
are almost parallel beyond the cross- vein. 
As in most large genera, we have some species which are 
rather difficult to place if we have only the female; the exceptions 
that I know of among the North American species are, Hercos- 
tomus metatar satis Thomson and H. vetius Melander, in which 
the bend in the last section of fourth vein is small, and Gymnop- 
ternus corner gens Van Duzee, where these veins are decidedly 
convergent, but not as much so as in Hercostomus unicolor Loew. 
Two species which I have described some time ago as 
Paraclius ornatus and flavicornis should be placed in the genus 
Hercostomus, as both have the third and fourth veins convergent 
beyond the cross-vein, as in Hercostomus unicolor Loew. 
Gymnopternus fiavitarsis sp. nov. 
Male: Length 2.5 mm. Face very narrow below, blackish. 
Palpi black. Front green with whitish pollen. Antennae black; 
third joint small, scarcely as long as wide, somewhat rounded, 
scarcely pointed at tip ; arista basal, as long as the face. 
Thorax and abdomen green with white pollen; hairs on the 
abdomen black. Hypopygium black; its lamellae dark yellow 
with a narrow black border, fringed with rather long black hairs; 
inner appendages yellow with a few black hairs at tip. 
All coxae black, the hairs on anterior pair black, short on 
basal half, longer and with some bristles mixed with them 
towards the tip. All femora black with yellow tips, without 
longer hairs below. All tibiae wholly yellow. All tarsi yellow, 
only a little darker at tip. Posterior tibiae and tarsi not at all 
