From Robert McLachlan   13 March 1879

My dear Sir

I return the proof: it required only the slightest correction in the points you specially allude to.¹

The occurrence of caddis-worms between the leaves of Bromeliāē is of great interest: the subject was brought before a recent meeting of the Entomol. Soc., & is mentioned (with some details) in the Proceedings, which you no doubt have.²

I have a lot of interesting facts & specimens from Fritz Müller in Trichoptera. They only arrived a week or two ago, & I have not yet completed my observations on the materials.³

With regard to the fringed legs of the pupaē. The fringes exist chiefly in those families & genera that inhabit still or slowly-moving water. I have just been writing on the subject for Pt. viii of my work on European Trichoptera, which treats on the genus Rhyacophila & others— Ryacophila frequents the most rapid torrents & waterfalls.⁴ The legs of the pupa-e are not fringed— fringes would be useless. The pupa must reach the surface by some method other than by swimming, for if it attempted the latter, it would be swept down by the torrent. I imagine that it contrives to crawl along the rocks &c, until it reaches the surface, in which it is aided by very strong tarsal claws. In all Families of Trichoptera I should say the pupaē with unfringed legs are the most numerous.

D^r. Müller is doing good work on the habits of Brazilian Trichoptera; he naturally suffers from incomplete works of reference.⁵ He appears to fall in with my views as to the near relationship of Trichoptera & Lepidoptera, as opposed to the American school which disposes of all difficulties in the Linnean Order Neuroptera by calling it a collection of “synthetic types”, whatever that may mean!⁶

Yours very faithfully | R. M^cLachlan

C. Darwin Esq. FRS. &c &c