220 SEXUAL DIVERSITY 



of white spots and dashes, and on the hind wings 

 by two belts of bkie, broken into spots, one of the 

 belts narrow, the other exceedingly broad. ^ 



It is not a little remarkable that in all these 

 examples, and indeed in very nearly all that have 

 come under my notice, this sexual diversity is dis- 

 played only upon the upjier surface of the wings, 

 and almost invariably upon the fore wings,^ a 

 mark of ancestry and of the lower position of 

 moths, in which the hind wings are covered by the 

 front wings in repose, and are as a rule less orna- 

 mented by diverse patterns. We might perhaps 

 anticipate the restriction of the characteristics to 

 the fore wings, since upon the upper surface the 

 complication of colorational design in butterflies 

 is greater on these than on the hind wings; yet 

 this same reasoning makes their restriction to the 

 upper surface the more striking, since the under 

 surface of the hind wings of butterflies is usually 

 more variegated than any other part. 



1 Here, however, as is shown elsewhere, the difference is 

 really due to another disturbing element, mimicry. 



^ De Nic^ville states that in Ergolis, a genus of oriental 

 Nymphalidae, the males have a large patch of glistening 

 scales on the under surface of the fore wings {Butt. India, ii. 

 8) ; and what under the circumstances is curious, these but- 

 terflies always settle with expanded wings. 



