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Show 40-.1: SEXUAL SELECTION. PART IL that the less brilliant colours of the female have been specr. all y o-a.m ed m. a ll or a lm os t a1 1 cases for the sake of protect~w n. 0 n tl1 e con t rar· y 1·t seems to m. e .m ore probable that the males alone, in the large maJonty of cases, h ave acqm. r eel ther"r· brioo- ht colours th. rough se'£x.u dal se l ec tw. n, the .1!.' e males havinoo· been but httle modi e . 11. d · Co nsequen tly tl1 e Jl'. 'emales of di•s tinct but a Ie speCies ou o· ht t o resem ble each other much mo.r e . closely than do the males of the same species ; and tlns IS the gener~l . 1 The females thus approximately show us the pn-ru e. · f th t mm·dial colouring of the parent-specres o e group o 'rhich they belong. They have, however, almost always been modified to a certain extent by some of the ~ucces- sr.v e st eps of var·I·atr'on ' throuoo· h the . accumul.a tiOn of which the males were rendered beautiful, havm? b~en t rans f.e rre d t o them . rrhe males and females of allied though distinct species will also generally hav~ been exposed during their prolonged larv~l s~ate to dlfferen~ conditions, and may have been thus mduectly affected, though with the males any slight change of colour thus caused will often have been completely ma.sked by the brilliant tints gained through sexual selectiOn. When we treat of Birds, I shall have to discuss the whole question whether the differences in colour ~etween. the males and females have been in part spe:1ally gamed by the latter as a protection; so that I will here only give unavoidable details. In all cases when the more common form of equal inheritance by both sexes has prevailed, the selection of bright-coloured males would ten_d to make the females bright-coloured; and the selectiOn of dull-coloured females would tend to make the males dull. If both processes were carried on simultaneously, they would tend to neutralise each other. As far as I can see, it would be extremely difficult to change through selection the CHAP. XI. DUTTERFLIES AND l\10THS. 405 one form of inheritance into the other. But by the selection of successive variations, which were from the first sexually l1mited in their transmission, there would not be the slightest difficulty in giving bright colours to the males alone, and at the same time or subsequently, dull colours to the females alone. In this latter manner female butterflies and moths may, as I fully admit, have been rendered inconspicuous for the sake of protection, and widely different from their males • Mr. Wallace 22"has argued with much force in favour of his view that when the sexes differ, the female has been specially modified for the sake of protection; and that this bas been effected by one form of inheritance, namely, the transmission of characters to both sexes, having been changed through the agency of natural selection into the other form, namely, transmission to one sex. I was at first strongly inclined to accept this view ; but the more I have studied the various classes throughout the animal kingdom, the less probable it has appeared. Mr. \Vallace urges that both sexes of the Heliconidm, Danaidm, Acroeidm are equally brilliant .because both are protected from the attacks of birds and other enemies, by their offensive odour; but that in other groups, which do not possess this immunity, the females have been rendered inconspicuous, from having more need of protection than the males. This .supposed difference in the " need of protection by the ~' two sexes " is rather deceptive, and requires some .discussion. It is obvious that brightly-coloured individuals, whether males or females, would equally attract, .and obscurely-coloured individuals equally escape, the 22 A. R. Wallace, in 'The Journal of TraYcl,' vol. i. 186R, p. 88. 'Westminster Review,' July, 1867, p. 37. See also l\:Iessrs. Wullflce -aud Bates iu 'Proc. Ent. Soc.' Nov. 19th, 186G, p. xxxix. |