Inter sexual forms of Plebeius argus L. 235 



mentary ovaries, ovotestes or an ovary and a testis. lie 

 has shown by cytological examination that these inter- 

 sexes all possess the second and third (autosomal) chromo- 

 somes in triplicate and the X-chromosome in duplicate, 

 and that some have the fourth chromosome in triplicate 

 and some in duplicate, and some have a Y-chromosome 

 and others are without it. He draws the conclusion that 

 in this species the sex is due to a balance between the 

 X and the autosomal chromosomes, the fourth chromosome 

 having genes with a disproportionately large influence 

 in producing male characters. Of the four kinds of inter- 

 sex differing in their chromosome complex, two were 

 recognisable in their structural characters. Those with 

 a triploid fourth chromosome were mainly male, those 

 with a diploid fourth chromosome were mainly female 

 in structure. Using X for the X or sex chromosome and 

 A for each set of autosomal chromosomes, individuals 

 with 2X : 2A, 3X : 3 A and ? IX : lA were all females, 

 although in normal DrosopJiila those with IX are males, 

 those with 2X : 3A were intersexes and those with 3X : 2A 

 or IX : 3A were sterile females and sterile males respectively. 

 The original brood from which he obtained his intersexes 

 produced 96 females, 9 males and 80 intersexes. Ten per 

 cent, of the females were structurally unlike the rest and 

 these produced more intersexes. 



It is evident that intersexes in insects may be produced 

 in different ways and that every case requires special 

 investigation. The intersexes of Agriades and Plebeius 

 differ in certain respects from any others, notably in the 

 unilateral distribution of male characters in the great 

 majority of them. They appear to have most in common 

 with Bridges' Drosojihila. In these there was a great 

 excess of females and intersexes over males, and the 

 intersexes themselves were of more than one kind. The 

 Lycaenid intersexes occur in places where females are 

 in great excess over males, and it is not unlikely that the 

 intersexes are of two kinds, a commoner one with reduction 

 of the size of the wings and with blue scales and androconia 

 scattered over them, and a rarer one with no alteration 

 in size of wings, with streaks or large patches of blue 

 scaling but without androconia. 



The abnormality of the chromosomes cannot be identical 

 with that of Bridges' DrosopJiila, because in Lepidoptera 

 the female is the sex with only one X-chromosome and 



