The Evidence from Sexual CJiaracters. 237 



hardly believe that such a resemblance is disadvantageous 

 to the males, we must conclude that the females alone 

 have varied, and that these variations have been pre- 

 served and augmented by natural selection for the sake 

 of protection, and have been transmitted to the female 

 offspring alone. 



In two species of Birds of Paradise, Paradisia apoda 

 and Paradisia Papuana, the females differ from each 

 other more than do their respective males; the female of 

 the latter species having the under surface pure white, 

 while the female of P. apoda is deep brown beneath. 



The males of two species of shrikes ( Oxynotus) in the 

 islands of Mauritius and Bourbon, differ but little in 

 color, while the females differ much, so that the female 

 of the Bourbon species might at first sight be mistaken 

 for the young of the Mauritius species. In this case 

 there seems to be every reason for believing that the 

 female of the Mauritius species has varied, while the 

 male has remained unmodified. 



Semper states (Animal Life) on the authority of Dr. 

 Hagen that the females of many species of cave-beetles 

 are blind, while the males have perfect eyes. As we 

 may feel confident that these beetles are descended from 

 ordinary forms, we must regard this as an instance of 

 female modification. 



The remarkable shell which is secreted by the large 

 fan-like arms of the paper nautilus (Argonauta) occurs 

 in the females alone, and it probably owes its origin to 

 female modification, although it it not impossible that 

 our recent species may be descended from a form in 

 which the male had a shell. 



The most remarkable cases of female modification are 

 those which are presented by polymorphic insects. 



Papilio turnus is one of our common yellow butter- 



