228 On some Parthenogenefic Ciiirjnoinidte. 



identical M'ith C. innupta in all structural characters, 

 differing only in the much blacker colour of the whole body, 

 which is exhil)ited particularly in the broad confluent naeso- 

 notal stripes. It is a matter for speculation whether 

 C. innupta may not be a pale parthenogenetic form of 

 C. celeripes. However, it would seeiu to be impracticable to 

 test this possil)ility, since the male celeripes {■=alra, 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 w^hich the males and females are 

 similar in coloration, and in which, moreover, the male 

 antennae are hardly more hairy tiian those of the female, 

 lired specimens of this species (which is apparently uu- 

 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 is indispntable; since the females hatched from 

 isolated pupse prothiced 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 repro-^ 

 auction, it is easy to understand how the male sex may be 

 eliminated 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, etc., and that under the abnormal conditions 

 encountered in Nature by the spread to new localities of a 

 feniaie-producing parthenogenetic race, the male sex may i)e 

 gradually 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 

 centre where both sexes existed, and wheie conditions Mere 

 favourable to jiairing. Another possible explanation would 

 be that climatic conditions ])revented pairing during the 

 whole of one flight-season, leaving only unfertilized females 

 to perpetuate the species. 



* C. B. Williams, "Some Problems of Sex Eatios aud Partlieuo- 

 ger.esis,'' Journal of Genetics, vi. 1917, pp. 255-257. 



