296 Professor E. B. Poulton 07i Mimetic Forms of 



would not remain intermediate, but would split up, in 

 accordance with the Mendehan conception, into the parent 

 forms ; and we can thus understand the comparative 

 rarity of intermediates. But while this is almost certainly 

 true of the sub-species of dardanus in the W., S., and on the 

 E. coast of Africa, where the specialization of the female 

 forms has been carried to a high pitch, it is probably not 

 equally true of the sub-species iwlytrophus of the Kikuyu 

 Escarpment. 



(e) ProbaUe origin of planemoides from' early variants 

 of trimeni. 



The abundance of intermediates of all kinds among the 

 females of iwlytrophus and the relative numbers of the 

 ancestral form trimeni indicate a near approach to the 

 origin of the diverse female forms. It is probable indeed 

 that first-cross intermediates between the specialized forms 

 themselves would split up into the parent forms on the 

 Escarpment as in other parts of Africa : but it is by no 

 means equally certain that the intermediates between each 

 of them and their primitive ancestor trimeni would behave 

 in this manner. Only thus does it seem possible to ex- 

 plain the relative abundance on the Escarpment of inter- 

 mediates almost always exhibiting primitive characteristics, 

 viz. some approach to trimeni. 



It would be of the highest interest to breed any of the 

 sub-species of dardanus through several generations : 

 especially is this desirable in the case of iiolytrophus, 

 which is certain to yield results of the utmost importance 

 from many points of view. 



It is probable that 'planemoides arose from trimeni by a 

 combination of the varieties which were to produce ccnea, 

 hiirpocoon, and troplionius. The size and shape of the white 

 hind- wing patch probably arose from varieties on the way 

 to eenca, its whiteness from those which were forming 

 hvppoeoon, while the fulvous tint of the fore-wing was 

 a utilization in another direction of the characteristic 

 colouring of troplionius. 



The argument made use of with regard to iilanemoides 

 applies to all the other mimetic female forms ; for inter- 

 mediates between them occasionally occur probably in 

 every sub-species and in all parts of the area of distribution. 

 But while such varieties are not to be looked upon as 

 ancestral, the case is very different with the Escarpment 



