Ill] OLD-WORLD MIMICS 33 



and encouraged the development of mimetic forms 

 in the female. The original female stiU lingers in 

 Abyssinia though it is now accompanied by the two 

 mimetic forms niavioides and ruspirm. Over the 

 rest of the area occupied by dardanus the females 

 are always tailless and, with the exception of trimeni 

 and dionysus, wonderfully close mimics. Trimeni, 

 the intermediate form, provides the clue to the way 

 in which the mimetic females have been derived 

 from the male, viz. by the prolongation across the 

 fore wing of the dark costal bar already found in the 

 females of the Madagascar and Abyssinian races, 

 by the deepening of the dark edging to the wings, 

 and by the loss of the tail. Through the gradual 

 accumulation of small variations trimeni came from 

 the male-like female, and by further gradual accumula- 

 tion of small favourable variations the mimetic forms 

 came from trimeni. South of the equator the male- 

 like form and the intermediate trimeni have dis- 

 appeared owing to the stringency of selection being 

 greater. Moreover the hkeness of mimic to model 

 is closer than in the north, a further proof of the 

 greater stringency of natural selection in these parts. 

 Such in brief is the explanation in terms of mimicry 

 of the remarkable and complex case of dardanus. 



Although the Euploeinae are not represented on 

 the African continent, it is the headquarters of another 

 distasteful family of butterflies — ^the Acraeiiiae — ^which 

 is but sparingly represented in the Oriental region i. 



1 Acraea violae, the only representative of the group in S. India 

 P. M. 3 



