32 STUDIES IN AMERICAN EPHYDRIDAE (dIPTERA) 
beneath, and, in one group, their tibiae- are also ciliate beneath 
with a comb-like series of short, erect setiilae. In both sexes 
there are only three erect extensors on the middle tibiae, the 
fourth or preapical one being absent or very minute. 
The species may be separated into two rather poorly defined 
groups, which are well worthy of note but hardly of nomencla- 
toral recognition. These groups are based wholly on male sec- 
ondary sexual characters, namely, the ciliation of the middle 
femora and tibiae, the females apparently not showing any corre- 
lation. For this reason I have not considered the groups except 
in the arrangement of the species. They may be characterized 
as follows: 
IMiddle tibiae not ciliate riparia-group 
Middle tibiae ciliate cinerea-group 
The npana-group 
This group contains species which seem to be more generalized 
than any others in the genus. Some of the species are difficult 
to separate and it is probable I have been too radical in their 
treatment; but am at loss sometimes to decide whether or not a 
specimen or a small series represents a distinct species, or only 
an extreme variety of, or perhaps a subspecies of, another known 
or unknown species. My material, although the most extensive 
ever studied of the American species, is discouragingly lacking in 
large series of such forms. Consequently synonymy is liable to 
occur, but I prefer such to erroneous determinations or indis- 
criminate lumping. 
The species belonging here have the middle femora of the male 
weakly, and their tibiae not at all, ciliate. It is rather a hete- 
rogenous group and may not stand as here considered. 
Notiphila riparia M eigen 
1830. Notiphila riparia Meigen, Syst. Beschr., vi, 65. 
After comparing the American specimens with those of the 
European riparia, I can find no characters for specific differentia- 
tion, nor even of subspecific value. In comparison with our 
other species of this group, we find the present one more robust 
and with stouter bristles; the mesonotum is evenly colored, 
without any indication or suggestion of stripes, especially mesad of 
the intra-alar series, although isolated spots on the lateral margin 
and at the lateral roots of the scutellum, may be present. The 
