To A. R. Wallace 26 February 
Down. | Bromley. | Kent. S.E.
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
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].
Please cite as
Darwin Correspondence Project, “Letter no. 5420,” accessed on 11 February 2016, http://www.darwinproject.ac.uk/DCP-LETT-5420