Chap. XL] BUTTERFLIES AND MOTHS. 401 



• 

 surely not have been in any way injurious to each indi- 

 vidual male to have partaken by inheritance of the pro- 

 tective colors of the female, and thus to have had a better 

 chance of escaping destruction. In a group in which 

 . brilliant colors are so common as with butterflies, it can- 

 not be supposed that the males have been kept dull-col- 

 ored through sexual selection by the females rejecting the 

 individuals which were rendered as beautiful as them- 

 selves. "We may, therefore, conclude that in these cases 

 inheritance by one sex is not due to the modification 

 through natural selection of a tendency to equal inherit- 

 ance by both sexes. 



It may be well here to give an analogous case in an- 

 other Order, of characters acquired only by the female, 

 though not in the least injurious, as far as we can judge, 

 to the male. Among the Phasmida?, or spectre-insects, 

 Mr. Wallace states that it is often the females alone that 

 so strikingly resemble leaves, while the males show only 

 a rude approximation." Now, whatever may be the hab- 

 its of these insects, it is highly improbable that it could 

 be disadvantageous to the males to escape detection by 

 resembling leaves. 31 Hence we may conclude that the 



31 See Mr. Wallace, in ' Westminster Review,' July, 1867, pp. 11, 37. 

 The male of no butterfly, as Mr. Wallace informs me, is known to differ in 

 color, as a protection, from the female ; and he asks me how I can ex- 

 plain this fact on the principle that one sex alone has varied and has 

 transmitted its variations exclusively to the same sex, without the aid of 

 selection to check the variations being inherited by the other sex. No 

 doubt, if it could be shown that the females of very many species had been 

 rendered beautiful through protective mimicry, but that this has never 

 occurred with the males, it would be a serious difficulty. But the number 

 of cases as yet known hardly suffices for fair judgment. We can see 

 that the males, from having the power of flying more swiftly, and thus 

 escaping danger, would not be so likely as the females to have had their 

 colors modified for the sake of protection ; but this would not in the 

 least have interfered with their receiving protective colors through in- 



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