IO2 Studies in the Theory of Descent. 



in this manner attributes the entire coloration of 

 butterflies to sexual selection. The origin of 

 seasonal dimorphism appears to me to be against 

 this view, howsoever seductive and grand the 

 latter may seem. If differences as important as 

 those which exist between the summer and winter 

 forms of many butterflies can be called forth by 

 the direct action of a changed climate, it would be 

 extremely hazardous to attribute great importance 

 to sexual selection in this particular case. 



The principle of sexual selection appears to me 

 to be incontestible, and I will not deny that it is 

 also effective in the case of butterflies; but I believe 

 that as a final explanation of colour this agency 

 can be dispensed with, inasmuch as we see that 

 considerable changes of colour can occur without 

 the influence of sexual selection. 2 



8 [Eng. ed. Since this was written I have studied the orna- 

 mental colours of the Daphnidcs ; and, as a result, I no longer 

 doubt that sexual selection plays a very important part in the 

 marking and colouring of butterflies. I by no means exclude 

 both transforming factors, however ; it is quite conceivable, on 

 the contrary, that a change produced directly by climate may 

 be still further increased by sexual selection. The above given 

 case of Polyommatus Phlceas may perhaps be explained in this 

 manner. That sexual selection plays a part in butterflies, is 

 proved above all by the odoriferous scales and tufts of the males 

 discovered by Fritz M tiller.] [For remarks on the odours 

 emitted by butterflies and moths, see Fritz Miiller in " Jena. 

 Zeit. f. Naturwissen.," vol. xi. p. 99 ; also " Notes on Brazilian 

 Entomology," Trans. Ent. Soc. 1878, p. 211. The odoriferous 

 organs of the female Heliconincz are fully described in a paper 

 in "Zeit. f. Wissen. Zool.," vol. xxx. p. 167. The position of 



