To Armand de Quatrefages   3 July [1862]¹

Dear Sir

Although I know how much you are occupied, yet I venture to request the great favour of some information, which I think that you can give me (& allow me to quote on your authority) without very great trouble. I can find no account of any differences in the moths of the several races of the common silk-worm. I have been told by one person that they are all closely similar.² Is this really the case? Do not the moths from the cocoons of various shapes, with white & yellow silk, present any differences? I refer, of course, only to the supposed races of Bombyx mori.— If you have not attended to this small point, probably M. Guérin de Méneville would at once be able to answer.—³

As I am writing I will ask one more question: a person in England, who formerly kept many silk worms & even had persons from France to attend to them, assured me positively that the wings of the female moth, when she first came out of the cocoon, appeared less developed than those of the male; is this the case? but ultimately the wings of both males & females acquired the same degree (as I found by measurement) of imperfect development. I know your observations on the wings in your Études & have just quoted them in my M.S. work, which I am preparing on “Variation under Domestication”.—⁴

I can only trust to the great kindness, which you have several times showed me to forgive me for thus troubling you.— With sincere respect, I remain | Dear Sir | Yours faithfully | Ch. Darwin