200 Mr. F. W. raed on British Limnobiidae. 
are alike in their thoracic markings, and differ somewhat 
from de Meijere’s description, but he had no hesitation 
in regarding as D. lucida a specimen which I sent him, 
There is a male in the Cambridge Museum from St. Merryn, 
Cornwall (Lamb). 
D. patens Lundstr. I only know this as British from a 
female in the British Museum taken at Aviemore, Inverness, 
10 vin. 1911 (Lt.-Col. Yerbury). This agrees in most details 
with a female from Finland named by Lundstrém, and I 
have very little doubt as to the determination. The open 
discal cell may possibly not be constant. 
D. ventralis Schum. South Uist, Hebrides, 13 vi. 1906 
(B. Kinnear); Freshfield, Lanes., 29 ix. 1920 (H. Britten). 
The hypopygium (Pl. I. fig. 2) differs shghtly from de 
Meijere’s figure, but there can be little doubt of the 
identification. ‘The reduced palpi are diagnostic. 
D. chorea Mg. Verrall and de Meiyere both seem to me 
to have confused two quite distinct species under this 
name, both of them widespread and abundant. The one 
which I consider to be the true D. chorea is very variable 
in colour, but can be fairly easily recognised by the char- 
acters given in the key. In addition to these it differs 
shghtly but constantly from the allied species in the struc- 
ture of the hypopygium: the fleshy lower claspers are 
scarcely longer than broad, and the two spines on the 
“rostrum” (7.e. the inward projection of the fleshy 
claspers) are short, slightly shorter than the rostrum, just 
as in de Meijere’s figure. A peculiarity of this species, 
which I have not noticed in its allies, is that the newly- 
emerged fly frequently has a green body. 
D. mitis, Mg. This is the other common species which 
has been confused with D. chorea. The identification with 
Meigen’s mitzs is due to Goetghebuer and Tonnoir; it will 
be convenient to follow them and so avoid proposing a 
new name. Apart from the distinctions given in the key, 
which are usually, but perhaps not invariably applicable, 
this species differs from D. chorea in the male hypopygium : 
the fleshy lower claspers are much larger, and at least half 
as long again as broad, and the two spines on the “ rostrum ” 
are about twice as long as the rostrum itself. The hypo- 
pygium of D. affinis and D. lutea has an almost identical 
structure, and it is quite possible that these species are 
nothing more than the extreme dark and light forms of 
D. mitis ; such at least is the opinion of de Meijere (in 
