some Parthenogenetie Chironowide. 223 
These, I believe, are the only cases so far placed on record 
of the occurrence of parthenogenesis in this family of the 
Diptera ; but I am now able to add two others. 
Chironomus clavaticrus, Kieffer. 
(Tanytarsus flexilis, Bause, ? Linné.) 
During the month of May 1917 I collected some weeds 
and mud from a pond at Letchworth, Herts, in the hope of 
being able to discover the larve of certain Culicid, but was 
then only able to rear various species of Chironomid from 
the material. Among these were a number of specimens of 
a species which I determined later as Chironomus clavaticrus, 
Kieff. (Bull. Soc. Nat. Hist. Metz, xxviii. 1913, p.17). My 
interest in these was aroused in the first place by the fact 
that this very distinctively marked species had not been 
recorded from Britain, and was quite unrepresented in the 
collections at the British Museum and at Cambridge. 
Secondly, it was noticeable that all the specimens which 
hatched (about: forty) were females. Suspecting that this 
might be a case of parthenogenesis, I isolated a few pupz in 
a small closed receptacle. ‘Two females hatched, and each 
of these deposited an egg-mass, From these eggs larvae 
developed which produced female adults on August 16; eggs 
were laid parthenogenetically on Aug. 18, and produced 
larvee on August 23. These for the most part died young, 
owing, I believe, to lack of food; a few lived through the 
winter and became full-grown in June 1918, but for some 
reason unknown to me no adults hatched from them. 
I made a diligent search by sweeping with a net in the 
neighbourhood of the pond where the larve were obtained, 
but succeeded in finding only female specimens, and am 
inclined to believe that in this locality at least no males 
occur. It is interesting to note that the species was origi- 
nally described by Kieffer from females only, reared from 
larvee by Thienemann. It was also reared by Réaumur 
from larvee collected near Paris; he figures the larva and 
the female adult (Hist. Ins, ii. p. 179, pl. xiv. figs. 11-16). 
No other records of the adult of C. clavaticrus have been 
made, and the species is thus known only in the female sex 
at present. 
‘The discovery of the male—supposing it to exist—would 
be a matter of some interest, since it might give a further 
clue to the correct generic position of the species. From 
the characters of the adult female alone, and particularly on 
account of the entirely bare wings, Kieffer was no doubt 
