?viAi'. XI. Butterflies and Moths. 309 



some tropical species. Even within the same genus we often 

 find species presenting extraordinary differences between the 

 sexes, whilst 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 ovei 

 this whole discussion, informs me that he knows tw r elve 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. 5 In nine of 

 these twelve species the males rank amongst 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 w r e 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 usual type, for they are gaily decorated 

 almost like the males, but in a somewhat less degree. Hence in 

 these two latter species the bright colours of the males seem to 

 have been transferred to the females ; whilst in the tenth 

 species the male has either retained or recovered the plain 

 colours of the female, as well as of the parent-form of the genus. 

 The sexes in these three cases have thus been rendered nearly 

 alike, though in an opposite manner. In the allied genus Eubagis, 

 both sexes of some of the species are plain-coloured and nearly 

 alike ; whilst with the greater number the males are decorated 

 with beautiful metallic tints in a diversified manner, and differ 

 much from their females. The females throughout the genus 

 retain the same general style of colouring, so that they resemble 

 one another much more closely than they resemble their own 

 males. 



In the genus Papilio, all the species of the iEneas group 

 are remarkable for their conspicuous and strongly contrasted 

 colours, and they illustrate the frequent tendency to gradation 

 in the amount of difference between the sexes. In a few species, 

 for instance in P. ascanius, the males and females are alike; in 



5 See ab;o Mr. Bates's paper in the sanrc subject, in regard to 

 Pioc. Ent. Soc. of Philadelphia,' Diadema, in ' Transact. Entomolog, 

 1865, p. 206. Also Mr. Wallace on Sol. of London,' 1869, p. 278. 



