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Letter 6012

Wallace, A. R. to Darwin, C. R.

15 Mar [1868]

    Summary Add

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    Coloration of butterflies; brilliantly coloured females.

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    Commends CD on his paper on specific differences in Primula [J. Proc. Linn. Soc. Lond. (Bot.) 10 (1869): 437–54; reprinted and revised in Forms of flowers] as a test-case proving origin of real species.

Transcription

Hurstpierpoint

March 15th.

Dear Darwin

The only striking examples of brilliantly coloured females in the Pieridæ are among the mimicking Leptalis and females of Pieris. In every other group the females are less brilliantly coloured than the males on the upper side,—except where the colours are simply yellow, in which cases the females are quite as conspicuous as the males. In the genus Thyca, which I think to some extent a protected group, the females are dusky above but the under sides of both sexes are equally brilliant as in Pl. VII. f. 3. 3a.

In the genus Tachyris when the males are brilliant or of marked colours the females are dusky or of quite different tints. Thus T. celestina is clear ashy blue in the ♂, yellow in the ♀. (Pl. VIII. f. 6) but the under sides of both are of clouded pearly and ashy tints, doubtless protective.

I am delighted to see the title of your paper for the ``Linnæan'' on Thursday. ``Specific differences between Primula veris &c.'' I always thought you did not make half enough of this case. For if the Cowslip & Primrose can be proved to be producible from common parents, and if, in addition to the strongly marked structural & physiological specific differences they admittedly possess, they have also the test difference of almost complete sterility, then the whole question is settled, the challenge so often thrown down is accepted, and the ``origin'' of a real species is proved. I sincerely hope you have settled it, & will pin your opponents to this one case.

I shall be in town from Thursday 2nd. of April till Sunday, & if you are there still shall hope to have the pleasure of seeing you.

Have you yet any cartes of yourself? I saw a very good one in an album some time since but do not see them on sale anywhere.

Believe me | Yours very faithfully | Alfred R. Wallace—

    Footnotes Add

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    f1 6012.f1
    The year is established by the reference to `Specific difference in Primula' (see n. 5, below).
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    f2 6012.f2
    CD had received information from Henry Walter Bates on species of Leptalis (family Pieridae) that mimicked butterflies of the family Heliconidae (see Correspondence vol. 15, letter from H. W. Bates, 29 March 1867). Species formerly included in Leptalis are now in genera of the subfamily Dismorphiinae (for a recent checklist of the genera of the family Pieridae, see Braby 2005).
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    f3 6012.f3
    Wallace refers to plates accompanying his article, `On the Pieridæ of the Indian and Australian regions' (A. R. Wallace 1867b). Thyca is a synonym of Delias (see A. R. Wallace 1867b, plate VII, figures 3, 3a, and p. 416; see also Winhard 2000, p. 16, and plate 22, figure 9 and plate 23, figure 9).
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    f4 6012.f4
    Tachyris celestina is now Appias celestina (see A. R. Wallace 1867b, plate VIII, figure 6, and p. 416; see also Winhard 2000, p. 26, and plate 41, figures 7 and 10).
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    f5 6012.f5
    `Specific difference in Primula' was read at the Linnean Society on 19 March 1868.
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    f6 6012.f6
    Wallace was evidently under the impression that CD's paper, `Specific difference in Primula', would demonstrate that crosses between the cowslip (Primula veris) and the primrose (P. vulgaris) were sterile. For more on the concept of `physiological' species, see Correspondence vol. 14, letter from A. R. Wallace, 4 February 1866 and n. 5. In fact, CD's crossing experiments established that the Bardfield oxlip, P. elatior, was a distinct species and not a hybrid form.
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    f7 6012.f7
    According to Emma Darwin's diary (DAR 242), the Darwins returned to Down on 1 April 1868.
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