skip to content

Darwin Correspondence Project

From Virginius Dabney   18 October 1873

Princeton, New Jersey, U.S.A.

Oct. 18— 1873

Charles Darwin Esq., M.A., F.R.S. &c | London.

Dear Sir;

For two or three years I have been studying your works, & I have conceived the idea that you are a man who would not disdain a contribution to Natural History, be it ever so humble, even from one who makes no claim to be called scientific— I am thus emboldened to make known to you certain facts which I have observed, which seem to me to have some bearing upon the hypothesis which you have put forth in the “Origin of Species”— I am entirely aware that a child would treasure up a glittering pebble, the worthlessness of which a lapidary would know at a glance—& that such may be my case.

One of the most important products of my native state, Virginia, is, as you are doubtless aware, tobacco. The great foe to its cultivation is the so-called tobacco worm—a large caterpillar which is produced in myriads in the regions where the plant is cultivated largely—1 The tobacco-worm is, as far as I know, the only animal that feeds upon the leaves of this plant—but the converse is not true, for this caterpillar preys upon other plants as well. The enumeration of these plants will throw into relief a fact which has struck me so forcibly that I venture to call your attention to it—

I. First, then, this caterpillar feeds upon the tobacco plant, which is of the order of the Solanaceae.

II Upon the potato— of the same family

III Upon the tomato— likewise of this order.2

IV. The Horse-Nettle Night-shade (S. Carolinense)3 of the same family.

V. And, lastly the stramonium—4

All of these plants, and, so far as I know, only these plants, furnish food to the tobacco-worm— Here, then, we have five plants, so utterly unlike that no man save a botanist would even suspect them of being related, & yet this caterpillar knows practically, that they are of one family— he is botanist enough to class together, so far as his needs are concerned, the leaves of the tomato & those of the stramonium—the former a delicious & healthful vegetable—the latter not only poisonous but so noisome that a bruise from a cane causes the plant to emit an odor so disgusting that one is glad to escape from its neighborhood— It seems to me that this striking fact can be accounted for by the hypothesis that this worm began to feed upon these plants when the family consisted of but one species, & that it can to this day detect a certain central something in the smell or taste of the various species that reveals to him their relationship—or else, reared originally upon one he recognized the others when brought within his reach—

Per contra, hogs (at least in Virginia) refuse to eat either potatoes or tomatoes when raw, until taught by having them mixed with other food—showing that they too recognize a something in these two plants which reveals to them their poisonous ancestry— It would seem that these so-called omnivorous animals instinctively shun even the now nutricious species of a family by avoiding which their progenitors survived. It seems to me that this aversion of the hog for the potato is alone sufficient to upset all the old fashioned theories which establish the hypothesis you have advanced.

Your views are making steady progress in this country. They cause sleepless nights to many of our theologians, but, a few years hence, they will suddenly wake up to the fact (as in Sir Charles Lyell’s case) that Moses knew all about the struggle for existence & the survival of the fittest.5

With the highest respect I remain | Faithfully yours | V. Dabney

CD annotations

4.4 It would … advanced. 4.8] scored pencil
Top of letter: ‘(Instinct) | Hog case interesting’ pencil; square brackets in ms

Footnotes

The tobacco hornworm is the larval form of Manduca sexta, (the Carolina sphinx moth).
The tomato hornworm is the larval form of Manduca quinquemaculata, the five-spotted hawkmoth. Both the tobacco and the tomato hornworm (which are easily confused) feed on the foliage of various members of the family Solanaceae, including tobacco (Nicotiniana), the tomato (Solanum lycopersicum), the potato (S. tuberosum), and members of the genus Datura.
Solanum carolinense (Carolina horsenettle).
Stramonium (also known as jimson-weed or thorn apple) is Datura stramonium.
There is no evidence that Lyell believed that Moses knew about natural selection. On the antiquity of man (C. Lyell 1863, pp. 457–8, explicitly contrasts the Biblical view of the miraculous origins of language with that provided by natural selection.

Summary

Feeding habits of the tobacco worm; it eats only five plants, all very different, but of same botanical family.

Letter details

Letter no.
DCP-LETT-9099
From
Virginius Dabney
To
Charles Robert Darwin
Sent from
Princeton
Source of text
DAR 162: 1
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 9099,” accessed on 22 March 2019, http://www.darwinproject.ac.uk/DCP-LETT-9099

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

letter