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Darwin Correspondence Project

From Mary Treat   2 December 1874

Vineland, N. Jersey.

Dec. 2, 1874.

Dear Mr. Darwin.

I have been studying the bladder-bearing species of Utricularia off and on the last year, and am now fully satisfied that they are the most wonderful carnivorous plants that I have yet seen.1 The so-called little bladders seem to be receptacles for digesting animal food. Not only small animalcules are lured into these receptacles, but animals large enough to be distinctly seen with the naked eye; and by holding the little bladders up to the light the movements of the animals can be seen with the unassisted eye.

I have found the remains of several Cyclops2 in these bladders, and one living one apparently just incarcerated. But the largest animal, and one that seems most constant in these receptacles, is a snake-like larva with brush-like, telescopic feet— I cannot now recall its name—3 it is quite active when first imprisoned, thrusting out and drawing back its beautiful feet, but it is in such close quarters that this is about all it can do, coiled around as it is—the larger specimens with head and tail meeting.

Last evening I found one just incarcerated in a very transparent bladder, it being the sole occupant. It was very active with its telescopic feet and horns, but in the morning—some twelve hours having elapsed since my last observation—it had no longer the power of thrusting its feet in and out, it could only move the brush-like appendages, and a slow movement was visible in the dark intestine that traverses the length of the body; and now this evening, twenty-four hours having passed, no movement is visible in any part of the animal, but it is slowly disintegrating.

This is the history of many specimens that I have watched in the same way.

I never knew, not even a small animalcule to escape after once inside the bladder.

I have not heard of any one making observations on these plants, and so I thought mine of sufficient importance to announce to you.—

Yours respectfully | M. Treat.


Treat had earlier sent CD her observations on the insectivorous plant Drosera filiformis (the thread-leaved sundew; see Correspondence vol. 21, letter from Mary Treat, 28 July 1873). CD had not specifically asked her about Utricularia (bladderwort), but he and Francis Darwin had been observing the plant themselves (see letter to John Ralfs, 13 July [1874]). Treat published her observations in a letter to the editor dated 4 January 1875 and printed in the New York Tribune, 1 February 1875, p. 8; the letter was reprinted in Gardeners’ Chronicle, 6 March 1875, pp. 303–4. CD cited it in Insectivorous plants, p. 408 and n. Treat’s work was on U. clandestina (U. clandestina is a synonym of U. geminiscapa, the hidden-fruited bladderwort).
Cyclops is a common genus of freshwater copepods.
In Treat 1875, p. 660, Treat identified the animal as a larva of Chironomus, a genus of midges. Treat 1875, in the American Naturalist, was a corrected reprint of her article in the New York Tribune (see n. 1, above).


Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 29 vols to date. Cambridge: Cambridge University Press. 1985–.

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

Treat, Mary. 1875. Plants that eat animals. American Naturalist 9: 658–62.


Observations on the insects captured by Utricularia.

Letter details

Letter no.
Mary Lua Adelia (Mary) Davis/Mary Lua Adelia (Mary) Treat
Charles Robert Darwin
Sent from
Vineland, N.J.
Source of text
DAR 58.1: 109–10
Physical description
ALS 3pp

Please cite as

Darwin Correspondence Project, “Letter no. 9740,” accessed on 23 April 2024,

Also published in The Correspondence of Charles Darwin, vol. 22