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Darwin Correspondence Project

From Francis Walker   26 February 1863

Church End | Finchley

Feb 26th. 63

My dear Sir,

I am sorry that I have so long delayed sending you the names of the flies that I received from you1

They are as follows, 1 Eulophus Westwoodii Hymenoptera 2 Tetrastichus Diaphantus chalcidites 3 di caudatus 4 Scatopse brevicornis Diptera They frequent flowers, but the three first are parasitic, or lay their eggs in the bodies of larvæ.—

Believe me | Yours truly | F. Walker

CD annotations

Top of letter: ‘Insects with pollinia of Musk. Orchis—’2 ink


CD visited the British Museum when he was in London at the beginning of February (see letter from Frederick Smith, 11 February 1863, and letter from S. P. Woodward, 14 February 1863), and may have asked Walker to identify the insects on that occasion. Walker had worked particularly on the Hymenoptera, Diptera, and the Chalcids, and compiled numerous catalogues of the British Museum’s insect collections (Entomologist’s Monthly Magazine 11 (1874): 140–1). CD acknowledged Walker’s assistance in the identification of Diptera visiting British species of orchids in ‘Fertilization of orchids’, p. 142 (Collected papers 2: 139).
CD was evidently collecting information on the insect pollinators of the musk orchis Herminium monorchis (see also Correspondence vol. 10, letter from Frederick Smith, 28 June 1862). His conclusions were incorporated into ‘Fertilization of orchids’, p. 145 (Collected papers 2: 142) and Orchids 2d ed., p. 61, where CD stated: When the first edition of this book appeared I did not know how the flowers were fertilised, but my son George has made out the whole process, which is extremely curious and differs from that in any other Orchid known to me. He saw various minute insects entering the flowers, and brought home no less than twenty-seven specimens with pollinia (generally with only one, but sometimes with two) attached to them. These insects consisted of minute Hymenoptera (of which Tetrastichus diaphantus was the commonest), of Diptera and Coleoptera, the latter being Malthodes brevicollis. CD’s notes on George Howard Darwin’s observations, dated 22–7 June 1862, are in DAR 70: 32–6.


Identifies flies sent to him by CD. [CD note states that these were found with orchid pollinia adhering to them.]

Letter details

Letter no.
Francis Walker
Charles Robert Darwin
Sent from
Source of text
DAR 181: 3
Physical description
1p †

Please cite as

Darwin Correspondence Project, “Letter no. 4014,” accessed on 17 June 2019,

Also published in The Correspondence of Charles Darwin, vol. 11