232 SEXUAL DIMORPHISM 



whether the mutual resemblance between protected and 

 mimicking species can be due to the "coincident adaptation 

 of the two analogues to similar physical conditions." He 

 rejects the conclusion as an explanation of definite mimicry, 

 but thinks that facts of similar variation in two already 

 nearly allied forms do sometimes show that they have been 

 affected in a similar way by similar conditions. 



The genus Hypolimnas affords an excellent example of 

 unisexual mimicry. 1 In Hypolimnas bolina there is compara- 

 tively little difference between the sexes, in H. misippus 

 there is a great deal. In both species there are varieties, but 

 the males do not differ much from one another. The male of 

 H. misippus is similar to that of H. bolina, of which figures of 

 both sexes are given. These figures are taken from specimens 

 from Palawan in the Philippine Islands. The male of H. 

 misippus is smaller, and the white spot on the upper side 

 of the hind wing is larger and rounder. 



The commonest form of the female of H. misippus mimics 

 the commonest of all the Danainae, viz. Danais chrysippus, 

 and they both occur in India, the Malay Archipelago, Aden, 

 and South Africa. Danais chrysippus is of a brownish yellow 

 colour over the greater part of the wings, with a patch of 

 black and white on the apex of the fore wing, and a black 

 border with wdnte spots on the hind wing. 



In Africa 2 another form of Danais occurs which differs 

 from D. chrysippus in the fact that the yellow of the hind 

 wings is replaced by white except at the border. This form 

 was formerly described as a distinct species under the name 

 D. alcippus. It occurs in West Africa, Central Africa, and 

 Abyssinia, where chrysippus is absent, and in South Africa 

 close to, if not actually in the range of, chrysippus. A variety 

 of Hypolimnas, which we may call alcippoidcs, mimics D. 



1 See Colonel C. Swinhoe, Journ. Linn. Soc. Zool., vol. xxv. 1896, p. 339. 

 2 Arthur G. Butler, Proc. Zool. Soc, 1884, p. 478. 





