From H. T. Stainton   20 February 1868

Mountsfield, | Lewisham. | S.E.

February 20th 1868

My dear Mr Darwin,

I send this as a preliminary reply to your letter, to which I will reply more fully in a few days, though on some of your points I fear I can give you no information1

But speaking generally with reference to the numbers of the sexes I will give you the results of my experience; from 1838 to 1851 I was a very energetic collector of Lepidoptera, catching them in all ways & by all devices, but catching them mostly in the perfect state & doing very little indeed in breeding from the larvæ. But from 1851 to the present time I have been almost exclusively a breeder & have captured very few perfect insects.

Now the result of these two modes of operation has been very different; as a captor I should have said that the males were to the females as 10:1, or very nearly so.

As a breeder I can safely say that the females are to the males as 6:5, or 6:4, or perhaps even a numerically larger proportion. My own experience as a breeder refers exclusively to the MicroLepidoptera, but I have no reason to suppose that the rule is different in them to what it is in the other groups.2

The subject was forcibly impressed upon me some years ago, when breeding the species of the genus Elachista;3 of many of the species we hardly ever see a female & caught specimens are generally males; but directly we began to breed the females largely preponderated.

The relative numbers of the sexes can be only ascertained by breeding— the females are ordinarily so much quieter & more retired that they do not come before us like the males.

I am aware that this will be diametrically opposed to the information you receive from Wallace & Bates—but theirs is based on the observation of insects in the perfect state & you will observe that it exactly agrees with my observations whilst confined to the imago state.4

We had a little discussion on this matter at the Entl Socy last Monday, Mr Bates having mentioned the subject of your letter to him & Mr Smith speaking for the Hymenoptera quite agreed with me that the true proportions of the sexes can only be ascertained by breeding.5

Yours very sincerely | H. T Stainton

C. Darwin Esq

CD annotations

Top of letter: ‘Wild state male serves several females— | This must be known with silk moths.6 I think I have heard not’ blue crayon
2
CD reported Stainton’s remarks on the proportion of the sexes in the smaller moths in Descent 1: 310–11.
3
Elachista is in the family Elachistidae (grass leafminer moths).
4
CD had sought information on insects from Henry Walter Bates. See letter to H. W. Bates, 11 February [1868], and letter from H. W. Bates, 18 February 1868. CD compared the observations of Lepidoptera made in the field by Bates, Alfred Russel Wallace, and others with those made by breeders in Descent 1: 309–13.
5
Stainton refers to Frederick Smith. See letter from H. W. Bates, 18 February 1868 and nn. 1 and 3.
6
CD wrote on the proportion of sexes in silk moths in Descent 1: 309, 311.

Please cite as “DCP-LETT-5903,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-5903