8 Studies in the Theory of Descent. 



of the background to which they are exposed con- 

 tinually changes, and because, even with the best 

 adaptation to the background, the fluttering motion 

 of the wings would betray them to the eyes of 

 their enemies. 8 I attempted also to prove at the 

 same time that the diurnal Lepidoptera of our 

 temperate zone have few enemies which pursue 

 them when on the wing, but that they are subject 

 to many attacks during their period of repose. 



In support of this last statement I may here 

 adduce an instance. In the summer of 1869 I 

 placed about seventy specimens of Araschnia 

 Prorsa in a spacious case, plentifully supplied with 

 flowers. Although the insects found themselves 

 quite at home, and settled about the flowers in 

 very fine weather (one pair copulated, and the 

 female laid eggs), yet I found some dead and 

 mangled every morning. This decimation con- 



8 [Mr. A. R. Wallace maintains that the obscurely coloured 

 females of those butterflies which possess brightly coloured 

 males have been rendered inconspicuous by natural selec- 

 tion, owing to the greater need of protection by the former 

 sex. See " Contributions to the Theory of Natural Selec- 

 tion," London, 1870, pp. 112 114. It is now generally 

 admitted that the underside of butterflies has undergone pro- 

 tectional adaptation ; and many cases of local variation in the 

 colour of the underside of the wings, in accordance with the 

 nature of the soil, &c., are known. See, for instance, Mr. D. 

 G. Rutherford on the colour-varieties of Aterica Meleagris 

 (Proc. Ent. Soc. 1878, p. xlii.), and Mr. J. Jenner Weir on a 

 similar phenomenon in Hipparchia Semele (loc. cit. p. xlix.) 

 R.M.] 



