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Letter 5907

Darwin, C. R. to Stainton, H. T.

21 Feb [1868]

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    Discusses factors possibly influencing the sex of caterpillars. Is gathering information on sex ratios in insects and would welcome any cases in which males seem to outnumber females.

Transcription

Down. | Bromley. | Kent. S.E.

Feb. 21st

My dear Mr. Stainton

Though you are so kind as to say that you will write again, I must thank you at once for your letter, which is of the highest value to me.— Your results are most curious, & show what caution is requisite. Do you think it possible that breeding very young caterpillars under confinement & therefore not under strictly natural conditions could influence the sex. I do not recollect how soon the sexual organs are differentiated in Larvæ. Perhaps Sir J. Lubbock may know. It has been stated (but I cannot say that I quite believe it) by Knight that heat will determine the sex in unisexual flowers.

I have had a note from Mr. Trimen who advances the case of the Lasiocampa Quercus, a female of which taken at any time & brought out of doors will be surrounded by males: this looks very like an excess of males— I remember reading somewhere, I wish I knew where an extraordinary account of males finding females at great distances & coming down chimneys  Have you noticed other such cases, viz of many males pursuing one female.— I think I have seen this with Butterflies. But then here comes another doubt— May not the same male serve more than one female? or does male die after copulation? Do you know anything on this head?

I think I will write to Dr. Wallace of Colchester, who perhaps wd excuse my writing to him.— I do not know to whom to apply in France, but the proportional numbers of male & female silk-moths has probably been observed there. The whole subject is very intricate, far more so than I anticipated, but I have often found that by patiently collecting facts, or supposed facts, in relation to various classes, a dim ray of light may be gained. I am getting the results of breeding race-horses—short-horns & greyhounds, tabulated on a large scale.—

I hope I shall not utterly weary you.—

With cordial thanks | Yours very sincerely | Ch. Darwin

    Footnotes Add

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    f1 5907.f1
    The year is established by the relationship between this letter and the letter from H. T. Stainton, 20 February 1868.
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    f2 5907.f2
    See letter from H. T. Stainton, 20 February 1868.
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    f3 5907.f3
    John Lubbock.
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    f4 5907.f4
    CD refers to Thomas Andrew Knight. The statement alluded to has not been found in any publication by Knight.
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    f5 5907.f5
    See letter from Roland Trimen, 20 February 1868 and n. 13.
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    f6 5907.f6
    In Descent 1: 311, CD wrote: `It is well known that if a virgin Lasiocampa quercus or Saturnia carpini be exposed in a cage, vast numbers of males collect round her, and if confined in a room will even come down the chimney to her.'
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    f7 5907.f7
    Alexander Wallace.
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    f8 5907.f8
    CD obtained information on silk-moths from the Italian zoologist Giovanni Canestrini (see Descent 1: 309, 311).
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    f9 5907.f9
    See letters from W. B. Tegetmeier, [before 15 February 1868] and nn. 4 and 5, and [16--20 February 1868] and n. 2.
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