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Darwin Correspondence Project

From Robert McLachlan   24 February 1868

Forest Hill

24th. Feby. 1868.

My Dear Sir

I am exceedingly glad that my rough notes were of some interest to you.1 Owing to a slip of the pen either you or I have made a mistake— My note about polygamy in insects referred to Phryganidae & not to Ephemeridae.2

I send the following information concerning the possibility of hybrids occurring in Phryganidae. Dr. Aug. Meyer of Münster, a young German Entomologist, placed numerous species together with an idea of testing this subject.— (Vide Stett. Ent. Zeitung. 1867 p. 155).3 He found Limnophilus politus ♂ & lunatus ♀ paired; L. striola ♂ & Anabolia nervosa ♀; L striola ♂ & lunatus ♀. L. politus ♂ & flavicornis ♀.4 From this last couple fertile eggs were obtained & young larvae produced, but they died very young. This would tend to prove that the auxilliary anal appendices which present such prima facie infallible specific characters in these insects, are not really of such vast importance after all so far as reproduction is concerned, for most of the above species have remarkably different anal parts.5

I am | Yours very faithfully | R. McLachlan

C. Darwin Esq. F.R.S.

CD annotations

1.1 I am … Ephemeridae. 1.3] crossed ink
2.7 auxillary] double underl ink
2.8 specific … insects,] underl ink
2.8 not … importance 2.9] underl ink
2.9 for most … parts. 2.10] underl ink


See letter from Robert McLachlan, 21 February 1868. CD’s reply to McLachlan has not been found.
CD reported McLachlan’s account of unions between different species of Phryganidae (now Phryganeidae), based on the authority of August Meyer (Meyer 1867), in Descent 1: 342 n. 2.
Limnophilus is now Limnephilus; Limnophilus striola is now Limnephilus nigriceps.
In Descent 1: 342, CD wrote: ‘it has been suggested that slight differences in [abdominal] organs would suffice to prevent the intercrossing of well-marked varieties or incipient species, and would thus aid in their development’. He added, however, on McLachlan’s authority, that the functional importance of abdominal structures in male insects had ‘probably been overrated’.


Reports that when August Meyer confined several distinct species of Phryganeidae they coupled and produced fertile ova, indicating that some specific characters are not so important so far as reproduction is concerned [see Descent 1: 342 n. 2].

Letter details

Letter no.
Robert McLachlan
Charles Robert Darwin
Sent from
Forest Hill
Source of text
DAR 82: A86–7
Physical description
2pp †

Please cite as

Darwin Correspondence Project, “Letter no. 5924,” accessed on 17 June 2019,

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