To Alfred Newton 19 January 
Down. | Bromley. | Kent. S.E.
My dear Sir
Will you have the kindness to give me some information on one point? Not long since I was speaking to Mr Wallace about his mimetic butterflies,1 & I told him of the case of the Rhynchœa, of which the female is more beautiful than the male, with the young resembling the latter.2 He answered me that you at Nottingham had advanced this or some such case, & that you had simply explained it by the male being the incubator.3 I should be extremely obliged if you wd give me any information on this head & allow me to quote you. The subject interests me greatly, as in the 4th Edit. of the Origin I gave the obvious explanation of female birds not being gaudily coloured &c on account of their incubating;4 I knew then of the Rhynchœa but passed over the case from not having space & from its appearing to me quite inexplicable.
I hope that you will forgive me troubling you & believe me my dear Sir | yours sincerely | Charles Darwin
P.S. As I am writing, I will ask one other question, for the chance of your being able to answer it: Does the male black Australian swan, or the black & white S. American Swans, differ from the females in plumage? ie in the intensity of the black, or in the amount of black in the black-necked species?5
Seeks explanation of the case of the Rhynchaea, of which the female is more beautiful than the male, with the young resembling the latter. Wallace has told CD that at Nottingham AN explained this by the male being the incubator.
Does the male black Australian swan, or the black and white S. American swan, differ from the female in colour of plumage?
Please cite as
Darwin Correspondence Project, “Letter no. 5371,” accessed on 26 July 2016, http://www.darwinproject.ac.uk/DCP-LETT-5371