Mr. F. W. ‘Rawanda on British Limnobiidae. 213 
venation, but our specimens do not differ from E. taenionota 
in any noticeable manner, apart from the structure of the 
hypopygium. Most of the species of this genus vary in 
the smaller details of the venation, and it seems unsafe 
to base any specific distinctions on these characters. 
E. squalida Lw. This species is common at Norton 
Pond, Letchworth—a locality which has yielded quite 
a number of good things. It is of the size and build of 
E. flavescens, but of a brownish-ochreous colour, even on 
the wing-membrane. Mr. Cheetham has taken it at 
Gormire, Yorks. 
E. nielseni Meij. (1921) (Pl. I. fig. 10). 
Head, thorax, hypopygium and legs ochreous brown; palpi 
blackish; abdomen dingy greyish-ochreous; wings with the mem- 
brane clear, hairs light brown, moderately long; halteres uniformly 
dark brownish. Antennae of the male with the second scapal joint 
much swollen; first two flagellar joints almost globular; next three 
somewhat smaller and more elongate; remainder long and slender, 
with verticils about twice as long as each joint; in the female the 
second scapal joint is less swollen, and the terminal flagellar joints 
less elongate. Stem of cell R, considerably shorter than that of 
cell M,. Hypopygium (see fig. 10): side pieces simple, about three 
times as long as broad. Upper (inner) clasper scarcely darkened 
apically, with a hump some way before the rounded tip. Lower 
(outer) clasper somewhat swollen a little before the pointed black 
tip. Parameres short, simple, pointed, black-tipped. 
Several males and one female from Austwick, nr. Ingle- 
boro, 17 vii. and 27 viii. 1920 (C. A. Cheetham). The 
antennae resemble those of the flavescens group, but the 
body colour is not such a clear yellow. 
MOo.LopHiuus. 
The species of this genus are often very similar, but 
can be readily recognised by the striking differences in 
the male hypopygium; in many cases these characters 
cannot be seen well in the dry specimen; the end of the 
abdomen must be removed, cleared in potash and mounted. 
The following key will show which species are distinguish- 
able by other characters. Too much reliance should not 
be placed on the colour-differences indicated. 
