From C. O. Waterhouse    19 February 1868

My dear Sir,

I am very sorry for the delay there has been in answering your letter but it was almost unavoidable.¹ I do not know M^r. Murray’s paper on cave insects unless it be the same with the one I mentioned “On insect-vision & blind insects” (Edinb. New Philosoph. Journal. ser. 2. 1857. T. 6. p. 120 &c. fig.)²

This paper contains a list of all the cave insects. The Coleoptera are,

5 Anophthalmus (The species that I have seen are bright

polished, (somewhat pale) testaceous.)

3 Adelops³ (these are covered with fine golden pubescens which

makes them look less shining than the Anophthalmi, they are

testaceous-brown.)

1. Glyptomerus (described as being “rufo-brunneus, nitidus,

abdomine apice femoribus tibiisque posteriorbus

picescentibus”)⁴

1. Troglorhynchus⁵ (I have not yet seen a description of this)

3. Leptodirus (We do not possess this genus.)

The Brentus (or rather Taphroderes, Schönh.,) varies in length from $\frac{4}{12}$ to $\frac{7}{12}$ of an inch in the ♂—and from $\frac{9}{24}$ to $\frac{12}{24}$ of an inch in the ♀— The ♂ being small is quite exceptional—nearly all the ♂ are larger than the ♀.⁶

The species of the genus Taphroderes belonging to the 1^st. section (four species from S. America) do not present anything particular in form of mandible.⁷

I believe the thoracic horns in the Lamellicorns are used in escaping from beneath the ground or from the heart of trees (as the case may be) after the metamorphoses have been undergone.⁸

Since I wrote last I have seen the blind beetles Leptomastax said to be found “on the sands of the Bay of Beikos”— This is pale testaceous, very bright & polished.

Also Langelandia— I do not know the habits of this— It is an exception to the general rule in being dull & coarsely punctured & fuscous. Murray says “found underground”—⁹

I forgot in my last letter to answer your question about Brentus— It does belong to the first group of Curculionidæ.¹⁰

Hoping you will understand this disjointed rambling, | Believe me, | Yours very sincerely, | Chas. O. Waterhouse.

Chas. Darwin Esq^re.