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Darwin Correspondence Project

From Francis Walker   1 February 1861

Grove | Highgate

Febry. 1st. 61.

My dear Sir,

Mr. F. Smith has given me two Dipterous Species forwarded by you to him for the names.1 One “aboundant on T. officinalis” is Dolichopus nigripennis, (Fallén) a common species   The other “sucking Euphrasia” is Empis chioptera (Fallen) also common,2 the male with milk-white wings, very different in appearance from the dark-winged female.—3

I was not able to attend to the Aphides last year, but I will endeavour to make use of your suggestions respecting them & to study as much as I can, the inquiry as to species.—4

Believe me, yours sincerely, | F. Walker

CD annotations

1.2 T. officinalis”] ‘T.’ altered to ‘Tomentilla’ pencil
1.3 The other … female.— 1.5] crossed ink
2.1 I was … F. Walker 3.1] crossed pencil
Top of letter: ‘Ch 35 brown crayon


CD often sent insect specimens he wished to have identified to Frederick Smith, entomologist at the British Museum. Francis Walker was the author of numerous catalogues of the insect collections of the British Museum and of a three-volume monograph on Diptera for Insecta Britannica (London, 1851–6). Smith identified for CD the bees and other Hymenoptera found to be agents in orchid pollination, and Walker named the Diptera (see Collected papers 2: 139).
The Swedish entomologist Carl Frederik Fallén described Dolichopus nigripennis in Fallén 1814–27, 2: Dolichopodes, p. 15, and Empis chioptera in ibid., 1: Empidiae, p. 24.
CD was investigating the role of insects in pollinating plants. Tormentilla officinalis (see CD’s annotations, above) is another name for the herb Potentilla tormentilla, in which a ring-shaped nectary within the stamens is commonly visited by flies. Euphrasia has ‘loose-pollen’ flowers by which the visiting insect receives a shower of pollen from the anthers.
No earlier letter from CD to Walker giving ‘suggestions’ concerning aphids has been found. For CD’s expression of interest in the recent work on parthenogenesis in aphids, see Correspondence vol. 7, letters to John Lubbock, 30 [March? 1858] and [November 1858].
The reference is to chapter 3 of CD’s ‘big book’ on species, ‘On the possibility of all organic beings occasionally crossing, & on the remarkable susceptibility of the reproductive system to external agencies’ (see Natural selection).


Collected papers: The collected papers of Charles Darwin. Edited by Paul H. Barrett. 2 vols. Chicago and London: University of Chicago Press. 1977.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 26 vols to date. Cambridge: Cambridge University Press. 1985–.

Fallén, Carl Frederik. 1814–27. Diptera Sveciæ. 2 vols. in 1. Lund.

Natural selection: Charles Darwin’s Natural selection: being the second part of his big species book written from 1856 to 1858. Edited by R. C. Stauffer. Cambridge: Cambridge University Press. 1975.


Identifies two dipterous species of parasites [chalcidites].

Was not able to attend to the aphids last year, but will make use of CD’s suggestions and "study as much as I can the inquiry as to species".

Letter details

Letter no.
Francis Walker
Charles Robert Darwin
Sent from
Source of text
DAR 46.2 (ser. 3): 54–5
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 3053,” accessed on 21 November 2019,

Also published in The Correspondence of Charles Darwin, vol. 9