From Henry Walter Bates 18 March 1861
King St Leicester
18 March 1861
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
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)].
Please cite as
Darwin Correspondence Project, “Letter no. 3092,” accessed on 27 July 2016, http://www.darwinproject.ac.uk/DCP-LETT-3092