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Darwin Correspondence Project

To Thomas Belt   [7 August 1873]1

Down [Abinger Hall, Surrey.]


Dear Sir

Your account of the ants and their relations seems to me to possess extraordinary interest. I do not doubt that the excretion of sweet fluid by the glands is in your cases of great advantage to the plants by means of the ants, but I cannot avoid believing that primordially it is a simple excretion, as occasionally occurs from the surface of the leaves of lime trees.2 It is quite possible that the primordial excretion may have been beneficially increased to serve the plant. In the common Laurel (Prunus Lauro-Cerasus) of our gardens the Hive-bees visit incessantly the glands of the young leaves, on their under sides;3 and I should altogether doubt whether their visits or the occasional visits of ants was of any service to the Laurel. The stipules of the common Vetch secrete largely during sun-shine and Hive-bees collect the sweet fluid. So I think it is with the common Bean.4 I am writing this away from home, and I have come away to get some rest, having been a good deal overworked.5 I shall read your book with great interest when published, but will not trouble you to send the MS. as I really have no spare strength or time.6 I believe that your book, judging by the Chapter sent, will be extremely valuable, &

I remain | Dear Sir | Yours very faithfully | Ch. Darwin.


The date is established by the relationship between this letter and the letter from Thomas Belt, 2 August 1873; the first Thursday after 2 August 1873 was 7 August.
Prunus laurocerasus is now known as the cherry laurel. Its leaves resemble those of true laurels (Laurus), but it belongs to a different family and order. It has extrafloral nectaries on the lower leaf surfaces (for more on the function of extrafloral nectaries, see Capinera ed. 2008, pp. 2919–21). In Cross and self fertilisation, pp. 404, 423–4, CD discussed the relation between this plant and bees and wasps as well as ants. He concluded that ants did not protect the plant, but that protective relationships had developed in other cases, and cited Belt’s observations in support of this statement (ibid., p. 404).
Common vetch, Vicia sativa, and the bean V. faba secrete nectar from stipules throughout the flowering period. In Cross and self fertilisation, p. 403, CD discussed the secretion of fluid on the stipules of vetch in bright sunshine.
CD stayed at Abinger Hall, the home of Thomas Henry and Katherine Euphemia Farrer, from 5 to 9 August 1873 (‘Journal’ (Appendix II)).
See letter from Thomas Belt, 2 August 1873 and n. 2. CD refers to Belt 1874.


Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.


Discusses utility of plant secretions to ants.

Will read TB’s book when published [The naturalist in Nicaragua (1874)].

Letter details

Letter no.
Charles Robert Darwin
Thomas Belt
Sent from
Abinger Hall
Source of text
DAR 143: 78
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 8998,” accessed on 5 April 2020,

Also published in The Correspondence of Charles Darwin, vol. 21