Ɛpsilon

To C. V. Riley   28 September 1881

Down.

Septr. 28. 1881.

My dear Mr Riley.

I must write half a dozen lines to say, how much interested I have been by your “Further Notes” on Pronuba. which you were so kind as to send me.—1 I had read the various criticisms, & though I did not know what answer could be made yet I felt full confidence in your result, & now I see that I was right.—2 What an inaccurate man Mr Meehan is!3 His Epitaph ought to be “He retarded natural science in the U. States as much as any one man advanced it”— I see that he is to report on Vegetable Physiology on the next meeting of your association.4 If you make any further observation on Pronuba—it would I think be well worth while for you to observe whether the moth can or does occasionally bring pollen from one plant to the stigma of a distinct one for I have shown that the Cross-fertilisation of the flowers on the same plant does very little good; &, if I am not mistaken you believe that Pronuba gathers pollen from the same flower which she fertilises—

What interesting & beautiful observations you have made on the metamorphoses of the grass-hopper destroying insects—!5

My dear Sir | Yours sincerely. | Ch. Darwin.

Copy

1
The copy of Riley’s ‘Further notes on the pollination of Yucca and on Pronuba and Prodoxus’ (Riley 1880) is in the Darwin Pamphlet Collection–CUL. CD had thought Riley’s earlier paper (Riley 1873) on the behaviour of the yucca moth Pronuba yuccasella (a synonym of Tegeticula yuccasella) ‘the most wonderful case of fertilisation ever published’ (see Correspondence vol. 22, letter to J. D. Hooker, 7 [April 1874]).
2
For critics of Riley’s work, see Sheppard and Oliver 2004, pp. 38–42.
3
At the 1879 meeting of the American Association for the Advancement of Science, Thomas Meehan had argued that although he had seen the yucca moth in abundance when Yucca angustifolia was in flower, the plant never produced fruit unless artificially fertilised; he therefore concluded that Riley’s observations were incorrect (Meehan 1879). Riley 1880, pp. 628–39, responds to Meehan’s criticism.
4
In August 1881, at the Cincinnati meeting of the American Association for the Advancement of Science, Meehan was invited to deliver a lecture to the biological section at the meeting in Montreal in 1882 (Proceedings of the American Association for the Advancement of Science 30 (1881): 386). Meehan’s Montreal address, titled ‘Variations in nature: a contribution to the doctrine of evolution and the theory of natural selection’, related his own views of evolution and natural selection to those of CD, for whom the ‘whole world’ was ‘in mourning’ (Meehan 1882, p. 438).
5
Riley was one of three entomologists who made up the United States Entomological Commission, which had been instructed to investigate the grasshopper problem; the first annual report of the commission included Riley’s investigation of the locust mite (Trombidium locustarum, a synonym of Eutrombidium locustarum), which differs so much in infancy and maturity that these forms were thought to belong to distinct genera. (Riley himself confused the anterior and posterior ends of the larval form, mistaking the mouth for the anus.) In its mature form, the mite devours the eggs that locusts lay underground; in the larval form, the mites attach themselves to locusts (usually under the wing) and suck the nutrients out of them (First annual report of the United States Entomological Commission for the year 1877, relating to the Rocky Mountain locust (Washington: Government Printing Office, 1878), pp. 306–13).

Please cite as “DCP-LETT-13360,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-13360