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Letter 6139

Doubleday, Henry to Darwin, C. R.

22 Apr 1868

    Summary Add

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    On proportion of sexes;

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    coloration of sexes in Lepidoptera.

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    Sexual attraction of female Saturnia carpini.

Transcription

Epping

April 22nd 1868

My dear Sir,

I have had very little spare time during the past ten days and you must kindly excuse my apparent neglect— my old friend Edward Newman always sends me the proof sheets of one of his monthly Periodicals to look over and correct, and I was obliged to return them to him the end of last week—and they occupied most of my time—

I will answer your questions with great pleasure as far as I able to do so—

I possess all the moths marked with a blue [TICK] and there is nothing in the colour of any one of them which would make it conspicuous among the allied species—

I must answer your Second question with a negative— the 130 species in which the males appear to be more numerous than the females are not gayer or more brightly coloured than the allied species in which the sexes appear to be more equal in number— my decided opinion is that an unusually fine and highly-coloured female moth is not more attractive to the males than an ordinary specimen— The males of the Lepidoptera are certainly principally attracted to the females by the scent emitted by this sex and the distance to which it is conveyed is astonishing— to us the minute drop of fluid is scentless but it will attract the males for three or four hundred yards at the least and probably much further— in April 1866 I placed two female Saturnia carpini confined in a small gauze cage on a ledge at the back of the house about four feet from the ground and about a yard from the wall of the house which is rather lofty— the wind was North-west and blew against the house— the two moths were left there by accident as I did not suppose any males would find them out—but about 2 o'clock in the afternoon I was surprised to see three or four flying round the cage and a great many came on that and three or four following afternoons— now the scent of a drop of fluid, not larger than a pin's head, must have been conveyed over the roof of our house—at least 40 feet high across a wide street, over the tops of the houses on the opposite side, and at least two hundred yards further before it could reach the fields— I saw many of the moths cross the street— they always come against the wind—

A great number of males came to some females last year in the same place— I have three or four females now just out of the chrysalis but the weather is so windy and wet that it is of no use putting them out

I will look over your letters again and if I can give you any more information you will soon hear from me again— I shall always feel great pleasure in serving you in any way in my power—

With best wishes believe me | My dear Sir | Yours very sincerely | Henry Doubleday

C Darwin Esq

P.S. Satyrus Anthe is not a very gay butterfly—orange and brown—like so many of the genus— there is very little difference in the colour of the sexes

    Footnotes Add

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    f1 6139.f1
    Doubleday probably refers to the Entomologist, which was edited by Newman. Newman was also editor of the Zoologist and natural history editor of the Field (ODNB).
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    f2 6139.f2
    See letter to Henry Doubleday, 15 April [1868].
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    f3 6139.f3
    Doubleday refers to a list of Lepidoptera CD had enclosed with his letter (see letter to Henry Doubleday, 15 April [1868] and nn. 2 and 3).
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    f4 6139.f4
    See letter to Henry Doubleday, 15 April [1868].
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    f5 6139.f5
    Saturnia carpini is now S. pavonia, the emperor moth. In Descent 1: 311--12, CD cited Doubleday on the attraction of large numbers of males of this species to captive females.
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    f6 6139.f6
    See letter to Henry Doubleday, 15 April [1868]. Satyrus anthe is now Chazara persephone, the dark rockbrown.
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