My dear M^r 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 Ent^l Socy last Monday, M^r Bates having mentioned the subject of your letter to him & M^r 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