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Darwin Correspondence Project

To A. R. Wallace   26 February [1867]

Down. | Bromley. | Kent. S.E.

Feb 26

My dear Wallace

Bates was quite right, you are the man to apply to in a difficulty. I never heard any thing more ingenious than your suggestion & I hope you may be able to prove it true.1 That is a splendid fact about the white moths: it warms one’s very blood to see a theory thus almost proved to be true.2 With respect to the beauty of male butterflies, I must as yet think that it is due to sexual selection; there is some evidence that Dragon-flies are attracted by bright colours; but what leads me to the above belief is, so many male Orthoptera & Cicadas having musical instruments. This being the case the analogy of birds makes me believe in sexual selection with respect to colour in insects.3 I wish I had strength & time to make some of the experiments suggested by you;4 but I thought butterflies wd not pair in confinement; I am sure I have heard of some such difficulty.

Many years ago I had a dragon-fly painted with gorgeous colours but I never had an opportunity of fairly trying it.

The reason of my being so much interested just at present about sexual selection is that I have almost resolved to publish a little essay on the Origin of Mankind, & I still strongly think (tho’ I failed to convince you, & this to me is the heaviest blow possible) that sexual selection has been the main agent in forming the races of Man.5

By the way there is another subject which I shall introduce in my essay, viz expression of countenance; now do you happen to know by any odd chance a very good-natured & acute observer in the Malay Arch. who you think wd make a few easy observations for me on the expression of the Malays when excited by various emotions? For in this case I wd send to such person a list of queries.6

I thank you for your most interesting letter & remain | yours very sincerely | Ch. Darwin


Henry Walter Bates had advised CD to ask Wallace about colourful caterpillars (see letter from A. R. Wallace, 24 February [1867] and n. 2). When he described his enquiry in Descent 1: 416, CD mentioned that Wallace had ‘an innate genius for solving difficulties’.
Wallace was not convinced that the bright colours of some male butterflies were a result of sexual selection (see letter from A. R. Wallace, 24 February [1867] and n. 8). CD eventually concluded in Descent 1: 399, 403–4, that bright colours in male butterflies and some male moths were generally a result of sexual selection rather than for protection. For CD and Bates’s earlier consideration of bright colours and sexual selection in butterflies, see also Correspondence vol. 9, letter to H. W. Bates, 26 March [1861], and letter from H. W. Bates, 28 March 1861 and n. 7. He reported the belief that the colours of dragonflies served as a sexual attraction in Descent 1: 361–2, and discussed the sounds made by cicadas and Orthoptera in ibid., pp. 350–61.
For Wallace’s suggested experiments, see his letter of 24 February [1867].
For CD’s intended publication on human descent, see also the letter to Edward Blyth, 23 February [1867] and n. 3. CD had tried in 1864 to convince Wallace that sexual selection had been a powerful influence in forming the human races (see Correspondence vol. 12, letter to A. R. Wallace, 28 [May 1864], and letter from A. R. Wallace, 29 May [1864]).
Ultimately, CD published Expression separately from Descent. See also letter to Fritz Müller, 22 February [1867] and n. 13.


ARW’s explanation of protective value of conspicuous coloration is ingenious.

CD still holds to sexual selection with respect to beauty in male butterflies.

Sexual selection and the races of man.

Expression of emotions is another subject he plans to include in his essay [Descent].

Asks ARW to suggest an observer in Malay Archipelago to whom he might send queries [on expression].

Letter details

Letter no.
Charles Robert Darwin
Alfred Russel Wallace
Sent from
Source of text
British Library (Add 46434, f. 76)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 5420,” accessed on 27 June 2017,

Also published in The Correspondence of Charles Darwin, vol. 15