To Alfred Russel Wallace 23 February 1867
Down, Bromley, Kent, S.E.
February 23, 1867.
I much regretted that I was unable to call on you, but after Monday I was unable even to leave the house.1 On Monday evening I called on Bates2 and put a difficulty before him, which he could not answer, and, as on some former similar occasion, his first suggestion was, “You had better ask Wallace.” My difficulty is, why are caterpillars sometimes so beautifully and artistically coloured? Seeing that many are coloured to escape danger, I can hardly attribute their bright colour in other cases to mere physical conditions. Bates says the most gaudy caterpillar he ever saw in Amazonia (of a Sphinx) was conspicuous at the distance of yards from its black and red colouring whilst feeding on large green leaves.3 If anyone objected to male butterflies having been made beautiful by sexual selection, and asked why should they not have been made beautiful as well as their caterpillars, what would you answer? I could not answer, but should maintain my ground.4 Will you think over this, and some time, either by letter or when we meet, tell me what you think? Also, I want to know whether your female mimetic butterfly is more beautiful and brighter than the male?5
When next in London I must get you to show me your Kingfishers.6
My health is a dreadful evil; I failed in half my engagements during this last visit to London.—7 Believe me, yours very sincerely, | C. Darwin.
Asks why caterpillars are sometimes beautifully coloured. It poses a problem for view that sexual selection is the explanation of colours of male butterflies.
More on mimetic butterflies.
Please cite as
Darwin Correspondence Project, “Letter no. 5415,” accessed on 7 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-5415