From Robert McLachlan   24 February 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. D^r. 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. M^cLachlan

C. Darwin Esq. F.R.S.