228 On some Parthenogenetic Chironomid. 
identical with C. innupta in all structural characters, 
differing only in the much blacker colour of the whole body, 
which is exhibited particularly in the broad confluent meso- 
notal stripes. It is a matter for speculation whether 
C. innupta may not be a pale parthenogenetic form of 
C. celeripes. However, it would seem to be impracticable to 
test this possibility, simce the male celeripes (=atra, Winn.) 
appears equally indifferent in captivity to females of celeripes 
or innupta. 
In considering the question of parthenogenesis in Coryno- 
neura, it may not be out of place to mention that a species 
exists in this country in which the males and females are 
similar in coloration, and in which, moreover, the male 
antenne are hardly more hairy than those of the female. 
Bred specimens of this species (which is apparently un- 
described) were sent me by Prof. J. W. Carr in 1914, and, 
being under the impression that all were females, I was at 
first inclined to regard this as another possible case of 
parthenogenesis ; it was only on mounting a specimen for 
detailed study that presence of males was discovered. In 
the case of C. innupta, however, the occurrence of partheno- 
genesis 1s indisputable; since the females hatched from 
isolated pupz produced eggs, there is no room for error on 
account of similarity of the : sexes. 
The question as to the origin of parthenogenetic species or 
varieties is too obscure to be profitably discussed, but, given 
the existence of forms which are capable of asexual reprc- 
duction, it is easy to understand how the male sex may be 
clipinated in a part or in the whole of the range of the 
species. It has been pointed out by Williams* that many 
insects will not pair except under special conditions of space, 
heat, moisture, ete., and that under the abnormal conditions 
encountered in Nature by the spread to new localities of a 
fenale-producing parthenogenetic race, the male sex may be 
eradually lost. According to this suggestion, the apparent 
non-existence of males of C. clavaticrus (and perhaps of 
C. innupta) might be due to their having spread from some 
ceitre where both sexes existed, and where conditions were 
favourable to pairing. Another possible explanation would 
be that climatie conditions prevented pairing during the 
whole of one flight-season, leaving only unfertilized females 
to perpetuate the species. 
* C, B. Williams, “Some Problems of Sex Ratios and Partheno- 
genesis,” Journal of Genetics, vi. 1917, pp. 255-257. 
