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Darwin Correspondence Project

To Henry Walter Bates   11 February [1868]1

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

Feb. 11

My dear Bates

I have just found that I much require information on the proportion of males & females throughout, as far as possible, the animal kingdom. Unfortunately I did not see this, or rather I saw it only obsurely, & have kept only a few references.—2 I am nearly sure you give facts in Amazonia.—3 Trimen gives some cases in Mauritius of males in great excess.4 I know I have got one reference of Wallace of female Butterflies in excess.5 This, I imagine, is much rarer; will you try & remember any cases whatever of female insects of any order (except in parthenogenetic cases) in excess.— I know the Brimstone6 & some other English Male Butterflies are in excess.— How is it with Lamellicorns; but perhaps the horned males wd. be most collected. Should you dislike asking for information at Ent. Soc. publickly; of which I was pleased to see you are President?7 How about male Dragon-flies? I know you will aid me if you can.—

Perhaps I will have my next Book, which is chiefly on Sexual Selection, illustrated by wood-cuts; in which case I shall have to supplicate for hints for good species to engrave. For instance is any insect better than common Stag-Beetle to show enormous development of mandibles in male; I rather think there is a splendid Beetle from Chiloe, which I collected.—8 As beggars say the smallest trifle will be gratefully accepted.—

I hope you have got my Book, but do not, I beg, write merely to thank for form sake9

My dear Bates | Yours very sincerely | & very troublesomely | C. Darwin


The year is established by the relationship between this letter and the letter from H. W. Bates, 18 February 1868.
This is the first extant letter from CD requesting information on the proportion of the sexes. CD gives his reasons for including this information in his study of sexual selection in Descent 1: 261, 263–5. The detailed results of his inquiries were reported in Descent 1: 300–15. CD’s notes on the subject are in DAR 81: 79–86, DAR 85: B1–68, and DAR 86. Notes specifically on butterflies are in DAR 85: B65–8.
In Descent 2: 309, CD cited information from Bates’s The naturalist on the River Amazons (Bates 1863) on the greater proportion of male butterflies.
CD cited Roland Trimen’s work on South African butterflies (R. Trimen 1862–6) on the preponderance of males in nineteen species in Descent 2: 310. His notes indicate that he was reading Bates and Trimen in December 1867 (DAR 81: 19–20).
CD cited Alfred Russel Wallace’s paper on Malayan butterflies (A. R. Wallace 1864) for the greater number of females in one species in Descent 1: 310.
The brimstone butterfly is Gonepteryx rhamni.
Bates was president of the Entomological Society of London in 1868.
The European stag beetle, Lucanus cervus, is discussed in Descent 1: 376–7. The beetle (Chiasognathus grantii) found on the island of Chiloe, Chile, in January 1835, is described in CD’s zoology notes (Keynes ed. 2000, p. 403). See also K. Smith 1987, p. 81. Chiasognathus grantii is illustrated in Descent 1: 377.
CD refers to Variation. Bates’s name appears on the presentation list for the book (see Correspondence vol. 16, Appendix IV).


Asks about proportions of male to female insects.

Letter details

Letter no.
Charles Robert Darwin
Henry Walter Bates
Sent from
Source of text
American Philosophical Society (B D25.339)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 5858,” accessed on 30 April 2017,

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