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Darwin Correspondence Project

From W. M. Canby   1 February 1873

Wilmington Delaware U.S.A.

Febr. 1st 1873

Mr. C. Darwin | Down, Beckingham, Kent, England,

Dear Sir,

My good friend, Prof. Gray has sent me your letter to him dated Jan. 8th 1873, in which you inquire about some observations I made upon Dionæa in 1867;1 and has requested me to reply to it.

You appear to have confounded the place where I reside (as above) with the town of the same name in the State of North Carolina near which the Dionaea is found, and thus to suppose that I can easily make observations upon the plant in its natural situation; while in fact I am several hundred miles from it. It is just possible however that I may go to Wilmington N.C. in May, and if so I shall be most happy to serve you in any way I can. At present I shall have to rely upon former notes and upon memory.2

As an answer to the first question you ask, in the first place I enclose the article published in “The Gardener’s Monthly” (Philadelphia) for Aug. 1868;3 and next you will find below about all that I can remember additional that would be pertinent to the subject. As to the specific point as to the size of the insects captured by the plant, I answer that while to some extent it selects its food (if it may be so called) it does not its captures; that is, it will catch everything it can large or small. The leaves will close abruptly upon small stones, sticks or straws, or in fact upon any thing which touches the sensitive hairs. Such substances as cannot be acted upon are rejected,—i.e. the leaves soon open without secreting their peculiar fluid and are soon ready for renewed operations. But as far as I can remember any insect from the size of a small fly a line4 or two in length, to a beetle, or other insect, of nearly the length of the leaf, would be closed upon, and if not too well protected, devoured. You will notice what is said of the centipede,—that I distinctly remember to have been of a length equal to a good sized leaf—say one inch. As to the proportion of “large” or “small” I cannot distinctly remember; but after what I have said it would be fair to suppose that within the limits mentioned above, it would probably be about the proportions of the insect, frequenting the neighborhood, except that those which habitually fly would probably be less liable to capture than those which crawl; and especially if they were rapid fliers, or were so small that they might fly through, or rather, over and close to the leaves without touching the hairs. As stated in the article I lost my plants before completing my observations. Among other things I neglected to find out whether the hairs were sensitive their whole length. If they are not but only at or near the extremity, it is evident that a very small insect might crawl over a leaf, and even touch a hair, without exciting it.

Now about the leaves becoming callous and unexciteable after “catching” an insect. I have several times known vigorous leaves to devour their prey three consecutive times. But ordinarily twice, or quite often once, was enough to render them unserviceable, although the mere closing upon an object was not sufficient to render them so. Leaves may be excited so as to close a number of times in quick succession, each time becoming weaker and responding to the touch more slowly, but after resting for some time they will recover almost their primal force. After a vigorous leaf has had a victim sufficiently long to cause a secretion of its fluid, the force with which it remains closed is very considerable; so that when the sides are drawn apart, they will close again with quite a loud “flap,” when released.5

If you desire further information please write as to the points you wish observations made upon. Then in case I should be able to see the plant in its native haunts, (which yet I fear is unlikely), I will endeavour to give you the required information.

I am, with great respect, very truly, | Yours, Wm. M. Canby


CD annotations

1.1 My … memory. 2.7] crossed pencil
3.2 “The … 1868;] underl red crayon
3.8 Such … operations. 3.10] scored red crayon and blue crayon
4.8 the force … released. 4.10] scored red crayon and ink


For Canby’s observations on Dionaea muscipula (Venus fly trap), made in 1867, see Correspondence vol. 15, letter from Asa Gray to J. D. Hooker, [after 6 July 1867]. Gray had enclosed Canby’s letter to him to be forwarded to CD; the letter described the way the plant captured insects.
CD’s annotated copy of Canby’s ‘Notes on Dionæa muscipula Ellis’ is in DAR 59.1: 20. CD referred to the article in Insectivorous plants, pp. 301, 313.
In measurement, a line is a twelfth of an inch.
CD cited Canby for this observation in Insectivorous plants, p. 308.


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Insectivorous plants. By Charles Darwin. London: John Murray. 1875.


At Asa Gray’s request, responds to CD’s questions about WMC’s observations on Dionaea and particularly about the size of the insects captured and the excitability of the leaves after an insect is captured.

Letter details

Letter no.
William Marriott Canby
Charles Robert Darwin
Sent from
Wilmington, Del.
Source of text
DAR 58.1: 25
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 8755,” accessed on 17 April 2021,

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