From G. R. Waterhouse   [after 2 March 1855]1

diag Anisotomidæ—2 Genus Triarthron— all the tarsi 5-jointed

Hydnobius— do— do—

Anisotoma— tarsi 5, 5, 4 (the 4 jts belonging to the posterr.

tarsi)

Cyrtusa— tarsi 5, 5, 4

Colenis— tarsi 5, 4, 4 (all the above were formerly included under one generic title i.e, either Anisotoma, or Leiodes 3 —with the exception of Triarthron which had not been discovered at that time)

Agaricophagus— tarsi 4, 3, 3

Liodes (or Leiodes) as now restricted—

Amphycillus

Agathidium These three genera form the second section of the Anisotomidæ accordg to Erichson,4 who says of the section that the males have the tarsi 5, 5, 4; the females 5, 4, 4 or 4, 4, 4—and in the genus Liodes which contains but 6 species, four of which have the tarsi in the females 5, 4, 4 & the remaining two ♀s have tarsi 4, 4, 4

Cryptophagidæ

Antherophagus tarsi ♂ 5, 5, 4

♀ 5, 5, 5

Emphylus— do— do—

Cryptophagus— do—

Paramecosoma tarsi in both sexes pentamerous

Atomaria— do— do—

Ephistemus— do— do—

Mycetophagidæ Tarsi 4 jointed. The anterior tarsi in the males 3-jointedramme with regard to the Aleocharidæ (to which group Homalota belongs)—there are many species in which the anterior tarsi are 4-jointed & the four posterior tarsi 5-jointed—others have all the tarsi 5-jointed, & some genera have 4 joints to all the Tarsi—Hygronoma for example. In the great genus Homalota (which contains far more species than any other genus of the family) the fore tarsi are 4 jtd. & the four hind tarsi 5-jointed—

Of the Staphylinidæ, by far the greater portion of the genera have all the tarsi five jointed—the most marked exceptions occur in the Oxyteli which have but 3 joints to the tarsi—some of the Proteinini also have the tarsal joints reduced to 35

CD annotations

1.1 Anisotomidæ] ‘Was genus Leiodes’ added pencil
2.1 Cryptophagidæ] ‘Sub. Fam’ added pencil
3.1 Mycetophagidæ] ‘Sub. fam’ added pencil; ‘close to former Family’ added pencil
Verso of first page: ‘Good case of Sexual difference in relation to difference in allied species— G. R. Waterhouse’6 pencil; ‘Ch. 7’ brown crayon
1
Dated by the relationship to the letter from T. V. Wollaston, 2 March [1855]. CD had asked Wollaston about the use of the number of tarsi in the classification of Anisotomidae, a family of beetles, with specific reference to remarks made in Wollaston 1855, p. 484 (see letter from T. V. Wollaston, 2 March [1855], n. 8). CD evidently followed up Wollaston’s reply with an inquiry to Waterhouse.
2
The list is taken from Erichson 1848, pp. 44 and 87. Waterhouse’s list was formerly in CD’s bundle of notes relating to ‘Laws of variation’, subsequently chapter 7 of Natural selection (pp. 279–338). Associated with the list is an undated slip in CD’s hand (DAR 47: 134a): [‘Tipulidæ vary with deficient tarsi or legs’ del pencil] Curtis says that number of joints of Tarsi differs in certain Staphylinidæ, viz Homalota Fralagria, Bladius—even variable in same species *or sexes [interl]? Waterhouse At the end of the note, CD added ‘(no)’, presumably in response to the information given by Waterhouse in the letter. He refers to John Curtis, author of British entomology (1824–39).
3
Waterhouse here inserted a footnote superscript that refers to a note stating: ‘These two names were synonyms—’.
4
Wilhelm Ferdinand Erichson, the German entomologist, extensively revised this and other families in the Coleoptera.
5
In Natural selection and Origin, CD referred to the importance for taxonomists of the number of joints of the tarsi and described instances where these features were highly variable, citing Westwood 1839–40 (Natural selection, p. 335). The same case was taken up in Origin (pp. 157–8), where he explained it as the result of the variations being ‘taken advantage of by natural and sexual selection, in order to fit the several species to their several places in the economy of nature, and likewise to fit the two sexes of the same species to each other, or to fit the males and females to different habits of life, or the males to struggle with other males for possession of the females.’
6
CD’s point was that ‘the secondary sexual differences between the two sexes of the same species are generally displayed in the very same parts of the organisation in which the different species of the same genus differ from each other’ (Origin, p. 157). This statement is followed in both Natural selection, p. 335, and Origin, p. 157, by an account of the variable number of tarsi (see n. 5, above).

Please cite as “DCP-LETT-1625,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-1625