From John Gould   10 May 1866

Gould refers to a humming-bird species found in Ecuador and first described as Trochilus benjamini by the French ornithologist, Jules Bourcier (see Bourcier 1851). Gould placed the species within a new genus, Urosticte; only the males of the species had white tips on their central tail-feathers (see J. Gould 1861a, pp. 110–11, and 1861b, 3: 190). CD may have discussed the bird with Gould during his recent stay in London from 21 April to 1 May. See also nn. 3 and 4, below.

CD had served on a committee appointed by the British Association for the Advancement of Science in 1842 to report on zoological nomenclature (see Correspondence vol. 2, letter to H. E. Strickland, 17 February [1842]). The committee drew up rules for the naming of species and genera that were widely accepted as standard by zoologists in most countries until the 1890s (Stresemann 1975, pp. 264–7). One of the rules stipulated that ‘the name originally given by the founder of a group or the describer of a species should be permanently retained’ (Strickland et al. 1842, p. 109). See also Correspondence vol. 2, letter to H. E. Strickland, 31 May [1842], and Correspondence vol. 4, letters to H. E. Strickland, 29 January [1849] and [4 February 1849].

Gould described the white-tipped central tail-feathers of Urosticte benjamini in An introduction to the Trochilidæ, or family of humming-birds (J. Gould 1861a, pp. 110–11). Although Gould remarked that the coloured feathers were displayed by males of the species to attract females, he concluded: ‘that ornament and variety is the sole object [of such markings], I have myself little doubt’ (J. Gould 1861a, p. 110). CD’s annotated presentation copy of J. Gould 1861a is in the Darwin Library–CUL; Gould’s description and remarks are underlined (see Marginalia 1: 342–4). The question of beauty in humming-birds had recently been raised by George Douglas Campbell, the Duke of Argyll, in a series of articles critical of CD’s theory of descent by natural selection (G. D. Campbell 1865, pp. 230–2; see letter from James Shaw, [6–10 February 1866] and n. 3). CD discussed Gould’s description of U. benjamini, and Campbell’s criticisms, in Descent 2: 151–2. CD argued that the white-tipped central feathers could be explained by the theory of sexual selection.

Gould refers to A monograph of the Trochilidae, or family of humming-birds, in which he noted that females of the species Urosticte benjamini had all but their two central tail-feathers tipped with white (J. Gould 1861b, 3: 190).

CD may refer to a pigeon breed in which the males alone had black striations. The breed is described in Chapuis 1865, which CD had recently consulted for his work on pigeons in Variation (see Correspondence vol. 13, letter to W. B. Tegetmeier, 2 June [1865], and this volume, letter to W. B. Tegetmeier, 16 January [1866] and n. 4). CD cited the case from Chapuis 1865 in Variation 2: 74, and Descent 1: 285, 293–4, 2: 157.