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Darwin Correspondence Project

From Henry Walter Bates   18 March 1861

King St Leicester

18 March 1861

Dear Sir

At last the Ent. Society have printed my paper & I am enabled to send you 〈a〉 copy according to promise.1

I do not know whether the peru〈sal〉 will repay your trouble, & I cannot point out especial passages embodying the facts most useful & interesting to you; the〈y〉 are scattered over the whole,—perhaps the concluding observations & those under the head of P. Hierocles are most to the point.2

I think there are about 3 points of interest arising from the review of the species of Papilio—& the genus from the precision of the specific characters & the great amount of material existing in collections is well calculated to illustrate them.— These are

1   The derivation of the Amazonian fauna. I confess I was not prepared for the result to which I was obliged to arrive after a close examination of the species & their distribution—viz: that the Guiana region must 〈ha〉ve been the seat of an ancient & peculiar fauna transmitted through vast lapses of time; & that thence was derived the fauna of the Amazon valley.—3 Also that it was still so rich in endemic species. Surely I am right in deriving the conclusion that there can have been no great extinction here 〈d〉uring the glacial epoch.4

2   The widely different variability of species when under different local conditions in localities widely apart— Let us suppose 4 species A B C D living at localities 1 & 2. A will be not in the least modified: B constant at 1 will be instable at 2: C will have become changed at 2 in all its individuals, but the change is so small that all will admit the difference to be that of a variety: whilst D will have become changed so much more considerably at 2 that every author will treat the form as a perfectly good species. Yet all the points of difference between D1 & D2 are similar to those between B1 & B2 and 〈C〉1 & C2, only they are greater in degree or more numerous

3   The permanency of local varieties after they have become established. It is still the favourite argument of our best naturalists that varieties will always return to their normal form & that they will inter breed & produce fertile offspring. This argument is derived from the observations of varieties produced by domesti〈cation〉—a false guide—such varieties are too rapidly made, to be compared with the slow alterations of the whole organism which takes place in nature & affects, I have no doubt, at length the reproductive elements.— In the genus Papilio there is a set of local varieties all connected by fine gradations of differences; & yet in one well established case two of these varieties exist in contact & do not show the slightest tendency to amalgamate.—5 It is a case exactly parallel to what would be if we were to find in the wild state a series of graduated local varieties between the horse & ass;— I thought it likely I should find in the Natural History of the Horse & ass some data to prove the parallel & turned to a paper by Blyth lately published on the varieties of wild ass.6 I was surprised to find how little was satisfactorily known on the subject & how uncertain & vacillating is the state of our knowledge of the species & varieties of these conspicuous animals.

With 〈re〉gard to the varieties of species involving modifications of their reproductive elements, a learned entomologist friend of mine, Mr Baly, has found in the chrysomelidæ, what he calls specific differences in the male organs of generation;7 he finds they 〈v〉ary between very closely allied forms,—but then he reasons I think falsely,—he says that the fact of the difference in these organs proves distinctness of species & thus he is proving to be distinct species forms which all Entomologists had agreed to consider as varieties.— It is very amusing to read (In the proc. Entl. Soc. I think September or October las) that he had received a large series of Donaciæ from N. America,— there were many doubtful forms amongst them & he has applied the test of these organs to prove whether they are distinct species or no.8

I hope you will excuse this rather rambling letter & favour me with your opinion on my pap〈er〉 at your earliest convenience

Yours sincerely | H W Bates

CD annotations

1.1 At last … epoch. 4.7] crossed pencil
6.1 3 The … animals. 6.16] crossed pencil
Top of first page: ‘2d Letter in Portfolio (4)— on Glacial action—Good.’ ink


Bates 1861a. Bates’s earlier letter to CD has not been found, but see CD’s response to it (Correspondence vol. 8, letter to H. W. Bates, 22 November [1860]). CD’s copy of this paper has not been located.
Bates 1861a, pp. 349–54 and pp. 341–2. In his concluding observations, Bates put forward the view that the Papilio species peculiar to the Amazon region were modifications of species from nearby regions such as Guiana. He cited CD’s argument that during the glacial period the refrigeration extended into equatorial regions, thus enabling species of temperate zones to pass from one hemisphere to another. Bates claimed that if this were so, it would have resulted in the extinction of many forms peculiar to the equatorial regions, and that this was not borne out by the present distribution of Papilio. In the section on P. hierocles, he pointed out that the existence of forms that seemed to serve as connecting links between P. hierocles and the similar species P. vertumnus provided an argument for classifying one as a variety of the other; yet, the two forms, although found in close association, never hybridised (Bates 1861a, pp. 341–2 n.).
This point is discussed in the concluding remarks of Bates 1861a, p. 352.
This conclusion, discussed in Bates 1861a, p. 352 (see n. 2, above), contradicted CD’s view that many tropical species became extinct during the worldwide cold period and were subsequently replaced by invading temperate flora and fauna (see Origin, pp. 376–9). For CD’s response to Bates’s observations, and his views on the problem of accounting for the distribution of tropical species, see the letter to J. D. Hooker, 18 March [1861] and the letter to H. W. Bates, 26 March [1861]. CD mentioned the opposition of Bates’s facts to his theory in the fourth edition of Origin (Origin 4th ed., p. 451).
Bates refers to P. hierocles and P. vertumnus. See n. 2, above.
Blyth 1859. An annotated copy of this paper, presented to CD by Edward Blyth, is in the Darwin Pamphlet Collection–CUL.
Joseph Sugar Baly had published several papers describing species of Chrysomelidae, the leaf beetles. Baly was describing some of the insects collected by Bates.
The discussion about using the generative organs of forms of Donacia (tree-dwelling beetles) as characters for taxonomic discrimination took place at a meeting of the Entomological Society of London on 3 September 1860 (Transactions of the Entomological Society of London n.s. 5 (1858–61), Proceedings, p. 128).


Sends his paper ["Insect fauna of the Amazon valley", Trans. R. Entomol. Soc. Lond. 2d ser. 5 (1861): 223–8, 335–61].

Points out three areas of interest arising from the study of the species of Papilio: the derivation of the fauna, the variability of the species, and the permanence of local varieties.

Discusses J. S. Baly’s views on specific differences in reproductive organs [Catalogue of the Hispidae in the collection of the British Museum (1858)].

Letter details

Letter no.
Henry Walter Bates
Charles Robert Darwin
Sent from
Source of text
DAR 160.1: 61
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 3092,” accessed on 19 August 2019,

Also published in The Correspondence of Charles Darwin, vol. 9