From A. R. Wallace 15 March 1
The only striking examples of brilliantly coloured females in the Pieridæ are among the mimicking Leptalis and females of Pieris.2 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.3
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.4
I am delighted to see the title of your paper for the “Linnæan” on Thursday. “Specific differences between Primula veris &c.”5 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.6
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.7
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—
Coloration of butterflies; brilliantly coloured females.
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.
Please cite as
Darwin Correspondence Project, “Letter no. 6012,” accessed on 22 October 2016, http://www.darwinproject.ac.uk/DCP-LETT-6012