316 THE DESCENT OF MAN. 



that we may suppose that they likewise do so in the wooing; and 

 in this case we can understand how it is that they have been 

 rendered the more beautiful. Mr. Meldola, from whom the fore- 

 going statements have been taken, says in conclusion: "Though 

 "I am not convinced of the action of sexual selection in produc- 

 "ing the colors of insects, it cannot be denied that these facts are 

 "strikingly corroborative of Mr. Darwin's views.'"^ 



As sexual selection primarily depends on variability, a few 

 words must be added on this subject. In respect to color there 

 is no difficulty, for any number of highly variable Lepidoptera 

 could be named. One good instance will suffice. Mr. Bates 

 showed me a whole series of specimens of Papilio sesostris and 

 P. childrenae; in the latter the males varied much in the extent 

 of the beautifully enamelled green patch on the fore-wings, and 

 in the size of the white mark, and of the splendid crimson stripe 

 on the hind-wings; so that there was a great contrast amongst 

 the males between the most and the least gaudy. The male of 

 Papilio sesostris is much less beautiful than of P. childrenae; 

 and it likewise varies a little in the size of the green patch on the 

 fore-wings, and in the occasional appearance of the small crimson 

 stripe on the hind-wings, borrowed, as it would seem, from its 

 own female; for the females of this and of many other species 

 in the ^neas group possess this crimson stripe. Hence between 

 the brightest specimens of P. sesostris and the dullest of P. chil- 

 drenffi, there was but a small interval; and it was evident that as 

 far as mere variability is concerned, there would be no difficulty 

 in permanently increasing the beauty of either species by means 

 of selection. The variability Is here almost confined to the male 

 sex; but Mr. Wallace and Mr. Bates have shown-* that the females 

 of some species are extremely variable, the males being nearly 

 constant. In a future chapter I shall have occasion to show that 

 the beautiful eye-like spots, or ocelli, found on the wings of 

 many Lepidoptera, are eminently variable. I may here add that 

 these ocelli offer a difficulty on the theory of sexual selection; 

 for though appearing to us so ornamental, they are never pres- 

 ent in one sex and absent in the other, nor do they ever differ 



2S 'Nature,' April 27th, 1871, p. 508. Mr. Meldola quotes Donzel, in 

 'Soc. Ent. de France,' 1837, p. 77, on the flight of butterflies whilst 

 pairing-. See also Mr. G. Fraser, in 'Nature,' April 20th, 1871, p. 489, on 

 the sexual differences of several British butterflies. 



^ Wallace on the Papilionidae of the Malayan Region, in "Transact. 

 Linn. Soc' vol. xxv. 1865, pp. 8, 36. A striliing case of a rare variety, 

 strictly intermediate between two other well-marked female varieties, 

 is given by Mr. Wallace. See also Mr. Bates, in 'Proc. Entomolog. 

 Soc' Nov. 19th, 1866, p. xl. 



