350 THE DESCENT OF MAN. 



again, what is the meaning of the colors being widely dif- 

 ferent in the males and females of certain species, and 

 alike in the two sexes of other species of the same genus? 

 Before attempting to answer these questions a body of 

 facts must be given. 



With our beautiful English butterflies, the admiral, pea- 

 cock, and painted lady (Vanessas), as well as many others, 

 the sexes are alike. This is also the case with the magnifi- 

 cent Heliconidse, and most of the Danaidae in the tropics. 

 But in certain other tropical groups, and in some of our 

 English butterflies, as the purple emperor, orange-tip, etc. 

 (Apatura Iris and Anthocharis cardamines), the sexes 

 differ either greatly or slightly in color. No language suf- 

 fices to describe the splendor of the males of some tropical 

 species. Even within the same genus we often find species 

 presenting extraordinary differences between the sexes, 

 while others have their sexes closely alike. Thus in the 

 South American genus Epicalia, Mr. Bates, to whom I am 

 indebted for most of the following facts, and for looking 

 over this whole discussion, Informs me that he knows twelve 

 species, the two sexes of which haunt the same stations 

 (and this is not always the case with butterflies), and 

 which, therefore, cannot have been differently affected by 

 external conditions.* In nine of these twelve species the 

 males rank among the most brilliant of all butterflies, and 

 differ so greatly from the comparatively plain females that 

 they were formerly placed in distinct genera. The females 

 of these nine species resemble each other in their general 

 type of coloration; and they likewise resemble both sexes 

 of the species in several allied genera found in various parts 

 of the world. Hence we may infer that these nine species, 

 and probably all the others of the genus, are descended 

 from an ancestral form which was colored in nearly the 

 same manner. In the tenth species the female still retains 

 the same general coloring, but the male resembles her, so 

 that he is colored in a much less gaudy and contrasted 

 manner than the males of the previous species. In the 

 eleventh and twelfth species the females depart from the 

 usual type, for they are gayly decorated almost like the 



*See also Mr, Bates' paper in " Proc. Ent. Soc. of Philadelphia," 

 1865, p. 206. Also Mr, Wallace on the same subject, in regard to 

 Diadema, in '' Transact. Entomolog, Soc. of London," 1869, p. 278. 





