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Darwin Correspondence Project

To B. D. Walsh   17 February [1868]

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

Feb. 17th

My dear Sir

I stupidly wrote to you a few days ago before I had looked through your papers with reference to sexual differences.1 I now find heaps of facts & reasoning,—the very dim recollection of which made me write.— I write now simply, if in time, to save you the trouble of answering my letter, for a week or two, by which time I may have more questions to ask!— But I may ask some now, & if you do not receive another letter in a week’s time, I shd be most grateful if you will write to me.—

I do not know the genera Gomphus & Hæterina (see Proc. Ent. Soc. Phil. Oct. 1863 p. 223, & p. 239): are these more allied to Ephemera or Libellula;2 but what I want to know most is whether the males & females differ conspicuously in colour, & whether males are more brilliant to our eyes than the females.

You say (p. 239) in the group vulgatissimus of Gomphus that the males are much more numerous than females;3 whilst in two closely allied species viz G. fluvialis & amnicola the females are 2 or 3 times as numerous as males.4 Now I want especially to hear how the sexes differ in these two last species, relatively to the sexual differences in the vulgatissimus group; & relatively to the general type of colouring of the genus. This will be of very great interest to me.— I have just been quoting long passage from you in Pract. Ent. on aids to seizing females chiefly in Coleoptera.5

In Papilio machaon sexes alike, in many species of Papilio I believe, the sexes are very different in colour: now can you tell me anything about inequality in number of sexes in the cases in which the sexes differ & do not differ in colour: you will see at once at what I am driving.

In Papilio Turnus & Argynnis Diana, are the males or females the most abundant.?6

Pray forgive me troubling you & begging all these favours—

Yours very truly | C. Darwin

I do not think I shall have anything more to write at present so shd. be extremely obliged for an answer whenever you can spare time.


Walsh noted the proportion of the sexes in Gomphus and Hetaerina in his article in the Proceedings of the Entomological Society of Philadelphia for October 1863 (B. D. Walsh 1863b, p. 223); CD’s annotated copy of the article is in the Darwin Pamphlet Collection–CUL. Gomphus (family Gomphidae, clubtails) is now in the same suborder (Anisoptera, dragonflies) as Libellula (family Libellulidae, common skimmers). Hetaerina (family Calopterygidae, broad-winged damselflies) is now in the suborder Zygoptera (damselflies). Ephemera is now in the order Ephemeroptera (mayflies).
Walsh considered Gomphus vulgatissimus to be a species ‘group’ (B. D. Walsh 1863, p. 239).
Gomphus fluvialis is now Stylurus notatus; G. amnicola is now Stylurus amnicola.
CD cited Walsh’s article in the Practical Entomologist (B. D. Walsh 1867a) in Descent 1: 341–2.
Papilio turnus is now P. glaucus (the tiger swallowtail); Argynnis diana is now Speyeria diana (the Diana fritillary).


Descent: The descent of man, and selection in relation to sex. By Charles Darwin. 2 vols. London: John Murray. 1871.


Has looked through BDW’s papers and finds heaps of facts on sexual differences. Asks questions on sexual differences in particular species.

Letter details

Letter no.
Charles Robert Darwin
Benjamin Dann Walsh
Sent from
Feb 17 68
Source of text
Field Museum of Natural History, Chicago (Walsh 12A)
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 5883,” accessed on 15 August 2020,

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