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Darwin Correspondence Project

To J. J. Weir   [6 March 1868]

6, Queen St. | Cavendish Sqe | W.

My dear Sir

I have come here for a few weeks for a little change & rest.1 Just as I was leaving home I received your first note & yesterday a second; & both are most interesting & valuable to me.—2

That is a very curious observation about the Gold-finches beak, but one would hardly like to trust it without measurement or comparison of the beaks of several male & female birds; for I do not understand that you yourself assert that the beak of the male is sensibly longer than that of the female.—3 If you come across any acute bird-catchers (I do not mean to ask you to go after them); I wish you would ask what is their impression on the relative numbers of the sexes of any birds, which they habitually catch, & whether some years males are more numerous & some years females.—

I see that I must trust to analogy, (an unsafe support) for sexual selection in regard to colour in Butterflies. You speak of the Brimstone Butterfly & genus Edusa (I forget what this is, & have no books here, unless it it is Colias) not opening their wings;4 in one of my notes to Mr. Stainton I asked him, (but he could or did not answer) whether Butterflies such as the Fritillaries with wings bright beneath & above, opened & shut their wings more than Vanessæ most of which I think are obscure on the under surface.5

That is a most curious observation about the red underwing moth & the Robin;6 & strongly supports a suggestion, (which I thought hardly credible) of A. R. Wallace viz that the immense wings of some exotic Lepidoptera served as a protection from difficulty of Birds seizing them. I will probably quote your case.—7

No doubt Dr Hooker collected the Kerguelen moth, for I remember he told me of the case, when I suggested in the Origin the explanation of the Coleoptera of Madeira being apterous; but he did not know what had become of the specimens.—8

I am quite delighted to hear that you are observing coloured Birds, though the probability, I suppose, will be that no sure result will be gained.—9 I am accustomed with my numerous experiments with plants to be well satisfied if I get any good result in one case out of five.—

With most sincere thanks for your great kindness— | My dear Sir | Yours very sincerely | Ch. Darwin

You will not be able to read all my book—too much detail— some of chaptr in 2d Vol. are curious I think.—10

If any man wants to gain a good opinion of his fellow men, he ought to do what I am doing   pester them with letters.—


CD was at 6 Queen Anne Street, London, and later 4 Chester Place, from 3 March to 1 April 1868 (CD’s ‘Journal’ (Correspondence vol. 16, Appendix II)).
See letters from J. J. Weir, [before 3] March 1868 and [before 5] March 1868.
In his letter of [before 5] March 1868, Weir had mentioned Triphaena pronuba (now Noctua pronuba), the large yellow underwing moth, being chased by a robin in his aviary.
Alfred Russel Wallace had made the suggestion in an article on protective mimicry ([A. R. Wallace] 1867b, p. 16). CD referred to Weir’s and Wallace’s remarks in Descent 1: 395.
See letter from J. J. Weir, [before 5] March 1868 and n. 11. CD had noted, referring to Joseph Dalton Hooker’s comments on his theory, ‘Hooker tells me that not only the few Coleoptera, but the one Lepidoptera at Kerguelen Ld. were apterous!’ (DAR 197.4; see also Correspondence vol. 5, letter from J. D. Hooker, [before 17 March 1855] and n. 4).
Weir described an experiment he planned to make, brightening the colour of a chaffinch, in his letter of [before 5] March 1868.
Weir mentioned receiving his copy of Variation in his letter of [before 5] March 1868.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.


Discusses beaks and relative numbers of the sexes of goldfinches.

Comments on sexual selection among butterflies.

Mentions Kerguelen moth collected by Hooker.

Comments on JJW’s observations on coloured birds.

Letter details

Letter no.
Charles Robert Darwin
John Jenner Weir
Sent from
London, Queen Anne St, 6
MR 6 68
Source of text
American Philosophical Society (Mss.B.D25.348)
Physical description
ALS 7pp

Please cite as

Darwin Correspondence Project, “Letter no. 5986,” accessed on 9 February 2023,

Also published in The Correspondence of Charles Darwin, vol. 16