Ɛpsilon

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 3’5 brown crayon
1
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).
2
The Swedish entomologist Carl Frederik Fallén described Dolichopus nigripennis (a synonym of Hercostomus nigripennis in Fallén 1814–27, 2: Dolichopodes, p. 15, and Empis chioptera in ibid., 1: Empidiae, p. 24.
3
CD was investigating the role of insects in the fertilisation of flowers. Tormentilla officinalis (see CD’s annotations, above) is a synonym of Potentilla erecta (erect cinquefoil), in which a ring-shaped nectary surrounded by stamens is commonly visited by flies. Euphrasia has ‘loose-pollen’ flowers by which the visiting insect receives a shower of pollen from the anthers.
4
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].
5
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).

Please cite as “DCP-LETT-3053,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-3053