388 SEXUAL SELECTION. Part II. 



other tropical groups, and with some of our English 

 butterflies, as the purple emperor, orange-tip, &c. (Apa- 

 tura Iris and Anthocharis cardamines), the sexes differ 

 either greatly or slightly in colour. No language suffices 

 to describe the splendour of the males of some tropical 

 species. Even within the same genus we often find spe- 

 cies presenting an extraordinary difference between the 

 sexes, whilst others have their sexes closely alike. Thus 

 in the South American genus Epical ia, Mr. Bates, to 

 whom I am much 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 therefore cannot have been dif- 

 ferently affected by external conditions. 3 In nine of 

 these species the males rank amongst the most brilliant 

 of all butterflies, and differ so greatly from the compa- 

 ratively 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 likewise resemble both sexes in several allied genera, 

 found in various parts of the world. Hence in accord- 

 ance with the descent-theory we may infer that these 

 nine species, and probably all the others of the genus, 

 are descended from an ancestral form which was coloured 

 in nearly the same manner. In the tenth species the 

 female still retains the same general colouring, but the 

 male resembles her, so that he is coloured 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 type of colouring which 



3 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,' I860, p. 278. 



