198 DIVERSITY OF THE SEXES 



becomes. As to the differences in the length of 

 the leg-joints, I have not discovered that they fol- 

 low any general law, although there are few of 

 our butterflies whose sexes do not vary in this 

 particular. This form of antigeny is most con- 

 spicuous in the Rurales, the family which in- 

 cludes most of our smaller butterflies, the blues, 

 coppers, and hair-streaks. The males of certain 

 coppers also present another curious feature in a 

 tumid swelling of the basal joint of the middle 

 and hind tarsi. Finally, the front legs of but- 

 terflies are frequently furnished with a spread- 

 ing brush of hairs, or the thighs and shanks of 

 the other legs are supplied with curious pencils 

 or fringes of long stiff hairs, which appear to have 

 much the same significance as similar adorn- 

 ments in higher animals. 



Darwin supposes that all these various male 

 appurtenances, which occur throughout the animal 

 kingdom, such as cocks' combs, peacocks' tails, 

 and other paraphernalia of the lords of creation, 

 have all arisen by sexual selection ; that one of 

 rival males being selected as a mate whose out- 

 ward charms are greatest. He certainly brings 

 powerful argument and a strong array of facts to 

 support this hypothesis. But what then shall we 

 say of the following illustration of sexual anti- 

 geny ; namely, the presence in many males 

 among butterflies, but in no females, of scales of 



