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Darwin Correspondence Project

To H. W. Bates   15 April [1868]1

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

April 15th

My dear Bates

Will you look at p. 2 of enclosed note (which please return for it has been & is precious to me), at passage with two blue lines, & tell me the name of the one Papilio, in which there is no difference in colour in the two sexes.2

Also should you call this one species a beautiful or plain one, either relatively to most other Butterflies or to the genus Papilio?—

As I am writing I will ask another question: in your communication to W. H. Edwards in Proc. Ent. Soc. of Philadelphia, you speak of the females of Argynnis Diana, Sagena, Paphia, Papilio Turnus, as departing from the type of their family.—3 Now are these more gaudy than their males? The black female of P. turnus cannot be considered so. With Argynnis are the above females mimetic? I suppose you do not know whether in the case of these species the males or females appear most numerous. I hear from Walsh & Edwards that with P. turnus the males are as 4 to 1 to the females.4

H. Doubleday has put me up to good way of estimating number of sexes, viz by priced German list, & the results are striking;5 thus with Butterflies out of 114 sp. & vars, in which the sexes differ in price (of course there is no difference in very common species) the males in every case but one are cheapest; so that according to this standard, on an average, there ought to be for every 100 females 143 males.—

To return to the female Butterflies, Wallace thinks in the Pieridæ that in all cases where the female is most beautiful she is mimetic.—6

My M.S. on Lepidoptera has run to greater length than I like, but has interested me much; & I owe 45 of my information to your great & unvarying kindness—

Yours very sincerely | Ch. Darwin


The year is established by the relationship between this letter and the letter from H. W. Bates, 20 April 1868.
The enclosure was probably Bates’s letter to CD of 12 March 1868, in which the section beginning with the phrase ‘1st class, both sexes’ has been double scored in blue crayon by CD. CD probably refers to a species of what Bates described as the ‘Æneas group of Papilio’ (see letter from H. W. Bates, 12 March 1868 and n. 5).
CD refers to Bates’s ‘Notes upon the variation of sexes in Argynnis Diana’ (Bates 1865), which had been communicated to the Entomological Society of Philadelphia by William Henry Edwards. CD’s annotated copy of the article is in the Darwin Pamphlet Collection–CUL. For the passage referred to by CD and scored in his copy of the article, see Bates 1865, p. 206. The butterflies mentioned are Argynnis diana (now Speyeria diana, the Diana fritillary), A. sagana (now Damora sagana, the Sagana fritillary), A. paphia (the silver-washed fritillary), and Papilio turnus (now P. glaucus, the tiger swallowtail).


CD has questions related to colour differences in the sexes of butterflies, especially in relation to HWB’s paper ["On variation in sexes of Argynnis diana", Proc. Entomol. Soc. Philadelphia 4 (1865): 204–7].

Mentions that his MS on Lepidoptera [for Descent] is longer than he intended and the information is four-fifths owed to HWB.

Letter details

Letter no.
Charles Robert Darwin
Henry Walter Bates
Sent from
Source of text
Cleveland Health Sciences Library (Robert M. Stecher collection)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 6120,” accessed on 21 May 2019,

Also published in The Correspondence of Charles Darwin, vol. 16