Dear Sir

I do not know whether you will excuse the liberty which I take in writing to you and begging a favour.

I have been corresponding with M^r H Doubleday on the relative number of the males & females in Lepidoptera, & he sent me your Lepidopt-doubletten list N^o X, that I might judge of the number of the males comparatively with the females, by their prices.² I have tabulated all the cases (excluding the moths with apterous females) & I find that in the Rhopalocera there are 113 species & vars. in which the males are cheaper & therefore apparently commoner than the females; & one case alone in which the female is cheaper. In the Heterocera there are 130 sp. & vars. in which the male is cheaper, and 11 sp. in which the female is cheaper.³ Now some English lepidopterists maintained in a discussion at our Entomolog. Soc. that in a state of nature the males are much more plentiful than the females; but that when bred from the caterpillar or egg-state the females are generally the most numerous.⁴ In a book which I am preparing I intend to specify the results above given from your published lists, and the favour which I wish to beg of you is that you will look through your list and kindly inform me whether in those cases in which the males are cheapest, and in a few cases in which the females are cheapest—whether the specimens have generally been caught in a state of nature, or have been bred from the caterpillar, or from the egg-state.⁵

If you will grant me this favour & allow me to quote the answer, I shall esteem it a very great kindness.

I beg leave to remain Dear Sir with much respect | yours faithfully & obliged | Charles Darwin