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Darwin Correspondence Project

To August Weismann   12 January 1877

Down, Beckenham, Kent [2 Bryanston Street, London.]

Jan: 12th. 1877

My dear Sir

I will send you in a few days a copy of a new Edit. of my Orchids, as I think the account of Catasetum tridentatum is worth your reading as a striking instance of atavism accompanied by sterility.1

I read German so slowly, and have had lately to read several other papers, so that I have as yet finished only half of your first essay and two-thirds of your second.2 They have excited my interest and admiration in the highest degree, and whichever I think of last seems to me the most valuable. I never expected to see the coloured marks on caterpillars so well explained; and the case of the ocelli delights me especially.3 I think that the enclosed extract will interest you; I confess that the view formerly seemed to me fanciful, but it does so no longer.4

Do you know Caligo eurolochus? Mr. Butler, one of our best Lepidopterists, showed me a specimen some years ago, and said that he believed the immense ocelli on the under side of the wings, served to frighten any animal which approached the butterfly from beneath.5

I told Mr. Butler your views about the stripes on caterpillars; and he told me that a friend who was a good collector, shewed him a bush of Ligustrum with excrement beneath it, from which circumstance he was sure that there was a caterpillar of Sphynx ligustri living on it; but Mr. B. and his friend could neither of them find it until they searched every branch from base to top.6 Mr. Butler also mentioned to me the case of a caterpillar with long thin hairs, standing out laterally, which make it very difficult to be discovered as it presents no defined outline.

There is one other subject which has always seemed to me more difficult to explain than even the colours of caterpillars, and that is the colour of birds’ eggs, and I wish you would take this up.7

I saw two or three days ago, Sir J. Lubbock, and he expressed the liveliest interest about your book.

With my best thanks, and much respect | I remain, my dear Sir | Yours sincerely | Ch. Darwin.

P.S.— Mr. Bates tells me of a clergyman, Mr. Hallins and another gentleman who have a most beautiful, accurate and large collection of drawings of all the stages of the caterpillars of British Lepidoptera. They cannot afford to publish the collection. Mr. Bates thinks that Mr. Hebbins would lend you his share of the drawings, if they would be of interest to you to examine them, but the other man, a Mr. Buckler is bitter against evolution and probably would not lend his share, which is the larger one.8 Please inform me whether you think an examination of the drawings would be useful to you, and then we could try. I am going to lend your book to Mr. Bates.



Orchids 2d ed. was published in January 1877 (Publishers’ Circular, 1 February 1877, p. 93). Weismann’s name is on CD’s presentation list (see Appendix IV). CD had expanded his discussion of the three sexual forms of Catasetum tridentatum (a synonym of C. macrocarpum). One of the forms CD discussed was the hermaphrodite Myanthus barbatus (a synonym of Catasetum barbatum); he remarked, ‘Myanthus, though having the organs of both sexes apparently perfect, is sterile; it has therefore had its sexual constitution disturbed, and this seems to have caused it to revert in character to a former state’ (Orchids 2d ed., p. 205).
Weismann had sent CD copies of the two essays in the series Studien zur Descendenz-Theorie: I. Ueber den Saison-Dimorphismus der Schmetterlinge (On seasonal dimorphism in butterflies; Weismann 1875), and II. Über die letzten Ursachen der Transmutationen (On the final causes of transmutations; Weismann 1876). CD’s heavily annotated copies are in the Darwin Library–CUL (see Marginalia rev. ed.).
For Weismann’s discussion of the adaptive value of ocelli on caterpillars, see Weismann 1876, pp. 96–110. Weismann concluded that the ocelli were defensive and noted that in some cases they helped caterpillars mimic snakes (ibid., p. 107).
CD probably forwarded the extract that had been sent to him by Henry Walter Bates describing a snake-like caterpillar (see letter from H. W. Bates, 11 January 1877 and n. 1).
The South American Caligo eurilochus (giant forest owl butterfly) has a large ocellus on the underside of each wing that resembles the eye of an owl; like most butterflies, it folds its wings together when at rest, so the underside markings are visible. Arthur Gardiner Butler was an assistant keeper of zoology at the British Museum.
Ligustrum is the genus of privets. Sphinx ligustri is the privet hawk-moth; its caterpillar is bright green with lilac and white stripes along the side.
In Origin 6th ed., pp. 213–14, CD mentioned that while Australian cuckoos preferred to lay their eggs in nests with similar coloured eggs, European cuckoos showed no such preference. CD did not discuss egg colour in any other context.
See letter from H. W. Bates, 11 January 1877 and nn. 2 and 3. John Hellins did the fieldwork for William Buckler, the artist who figured the caterpillars at various stages of growth (see also Buckler 1886–1901). ‘Hallins’ and ‘Hebbins’ are copyist’s errors.


Buckler, William. 1886–1901. The larvae of the British butterflies and moths. 9 vols. London: Ray Society.

Marginalia rev. ed.: Biodiversity heritage library: Charles Darwin’s library.

Orchids 2d ed.: The various contrivances by which orchids are fertilised by insects. By Charles Darwin. 2d edition, revised. London: John Murray. 1877.

Origin 6th ed.: The origin of species by means of natural selection, or the preservation of favoured races in the struggle for life. 6th edition, with additions and corrections. By Charles Darwin. London: John Murray. 1872.

Weismann, August. 1876. Studien zur Descendenz-Theorie. II. Über die letzten Ursachen der Transmutationen. Leipzig: Wilhelm Engelmann.


Comments on AW’s book [Studien zur Descendenz-Theorie (1875–6)], especially on mimicry in caterpillars.

Mentions sets of drawings of British Lepidoptera in all stages. Would AW like to see them?

Letter details

Letter no.
Charles Robert Darwin
Leopold Friedrich August (August) Weismann
Sent from
London, Bryanston St, 2 Down letterhead
Source of text
DAR 148: 348
Physical description
C 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 10784,” accessed on 12 September 2023,