376 SEXUAL SELECTION. [Part II. 



Danaidne of the tropics. But in certain other tropical 

 groups, and with some of our English butterflies, as the 

 purple emperor, orange-tip, etc. {Apatura Iris and An- 

 thocharis cardamines), the sexes differ either greatly or 

 slightly in color. Nq language suffices to describe the 

 splendor of the males of some tropical species. Even 

 within the same genus we often find species presenting an 

 extraordinary difference between the sexes, while others 

 have their sexes closely alike. Thus in the South Ameri- 

 can genus Epicalia, Mr. Bates, to whom I am much in- 

 debted 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 differently affected by external 

 conditions. 3 In nine of these species the males rank among 

 the most brilliant of all butterflies, and differ so greatly 

 from the comparatively plain females that they were for- 

 merly 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 accordance 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 colored 

 in nearly the same manner. In the tenth species the fe- 

 male 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 type of coloring which is usual with 

 their sex in this genus, for they are gayly decorated in 



8 See also Mr. Bates's paper in ' Proc. Ent. Soc. of Philadelphia,' 

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

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



