WCP377

[1]

Sumatra¹ (Lobo Raman,² 100 miles E. of Bencoolen³)

December 10th. 1861

My dear Bates⁴

I should have written to you before to thank you for your paper on the "Papilios",⁵ but I somehow never can post up my correspondence till I get into some savage wilderness like that in which I am at present. I have here read your paper with quiet attention & also with great pleasure and I trust it is but the first of a long series which will establish your own fame ^and at the same time demonstrate the simplyicity & beauty of the Darwinian philosophy.

Your paper is in every respect an admirable one, & incontestably proves the necessity of minute & exact observation over a wide extent of country to enable a man to grapple with the more difficult groups, unravel their syno[ny]my & mark out the limits of the several species & varieties. All this you have done & have besides established a very interesting fact in Zoological Geography that of the southern bank of the river⁶ having received its fauna from Guyana & not from Brazil.

There is however another fact I think of equal interest & importance, which you have barely touched upon, & yet I think your own materials in this very paper establish it: viz. that the river in a great many cases limits the range of species or of well marked varieties. This fact I considered was shown, by the imperfect materials I brought home, to obtain both in the Amazon & Rio Negro. I read a paper before the Zool[ogical]. Soc[iety]. on the Monkeys of the lower Amazon & Rio Negro in which I stated that in almost every case for 800 miles up the R.[io] Negro the species were different on the opposite banks of the river.⁷ Guyana species come up to the E. bank;— Columbian sp.[ecies] to the West bank, & I observed that it was therefore important that travellers collecting on the banks of large rivers sh[oul]^d. note from wh[ich]. side every specimen came. Upon this D^r. Gray⁸ came down upon me with a singular floorer:— [2] "Why" said he "we have specimens collected by Mr Wallace himself marked Rio Negro only" — I don't think I answered him properly at the time that those specimens were sent from near Barra⁹ before I had the slightest idea myself that the species were different on the opp[osite]. banks. In Mammals this fact was not so much to be wondered at, but few persons would credit that it would extend to Birds & winged insects. Yet I am convinced it does & I only regret that I had not collected & studied birds there with the same assiduity I have here, as I am sure they would furnish some most interesting results. However "revenons à nos papillons" [French: let's go back to our butterflies].

It seems to me that a person with no special knowledge of the district would have no idea from your paper that the species did not in almost every [1 word struck through, illeg.] instance occur on both banks of the river. In only one case do you specially mention a species being found only on the N. bank (Ergeteles¹⁰). In other cases, except when the insect is local & confined to one small district, no one can tell whether they occur on one or both banks. Obydos¹¹ you only mention once Barra & the Tunantins [Tonantins]¹² not at all. I think a list of the sp[ecies]. or var[ieties]. occurring on the S. bank or N. bank only sh[oul]^d. have been given and would be of much interest as establishing the fact that large rivers do act as limits in determining the range of species. From the localities you give it appears that of the 16 sp[ecies]. & sub. sp[ecies]. peculiar to Amazon 14 occur only on the S. bank. Also that of the Guyana sp[ecies]. all pass to the S. bank. These facts I have picked out. They do not appear. It would seem therefore that Gu[y]ana forms having once crossed the river have a great tendency to become modified, & then never recross. Why the Brazilian species should not first have taken possession of their own side of the river is the mystery. I sh[oul]^d. be inclined to think that the river bed is comparatively new,— & that the S. plains [3] were once continuous with Guyana,— a fact that Guyana is older than N. Brazil & after it had pushed out its alluvial plains into what is now N. Brazil an elevation on the Brazilian side made the river cut a new channel to the Northward leaving the Guyana sp.[ecies] isolated, exposed to competition with a new set of species, & thus led to their becoming modified as we now find them.

The phenomenon of a tract of country having been peopled from one now separated from it & not from that of wh[ich]. it forms a part, is too extraordinary not to require some special & extraordinary cause, & the one I have mentioned seems capable of producing the effects, & by no means improbable (however unexpected) in itself. The whole district is I fear too little known geologically to test the supposition. The N. mountains of Brazil ^however are of recent elevation, since fishes of the Chalk period, are found at great elevations heights. This would bring their elev upheaval into the tertiary period & it may have continued to a recent period. Now if there are no proofs of such recent upheaval in the S. Guyana mountains the theory thus far receives support.

I regret that your time was not divided more equally between the N. & S. banks,— but I suppose you found the S. so much more productive in new & fine things. I suppose you will turn now to the Coleoptera¹³ & give us the Cicindelidae¹⁴ on the same plain, & I hope you have made arrangements for a lot of copies, each part paged consecutively to form complete separate works when finished.

I am here making what I intend to [be] my last collection, but am doing very little in insects as it is the wet season & all seems dead. I find in those districts where the seasons are strongly contracted the good collecting time is very limited only about a month ^{or two} at beginning of dry & a few weeks at commencement of rains. It is now [4] two years since I have been able to get any better owing to bad localities & bad weather, so I am getting disgusted. When I do get a good place it is generally very good but they are dreadfully scarce. In Java¹⁵ I had to go 40 miles inland in the E part & 60 miles in W. to get to a bit of forest & then I got scarcely anything — Here I have had to come 100 miles inland (by Palembang¹⁶) & even here in the very centre of E. forest Sumatra the forest is only in patches & it is the height of the rains so I get nothing,— a longicorn¹⁷ is a rarity & I suppose I shall not get as many species in 2 months as I have done in 4 days in a good place. I am getting however some sweet little Lycaenidae¹⁸ which is the only thing that keeps me in spirits.

I hope to be home before the opening of the Exhibition,¹⁹ & look forward to seeing you in London though I fear my collections will be in dreadful confusion till towards the winter. I think my priv[ate]. coll[ection]. of Col[eoptera]. & Lep[idoptera].²⁰ will be probably more extensive in specimens than yours, as I have a complete series from every island & chief locality, (which amount to about 30,) and as I intend to ^re ticket, catalogue & arrange them all,— as well as my extensive collection of birds, I shall have work for years,— a labour of love to wh[ich]. I look forward with much pleasure.

Remember me kindly to your brother Frederick²¹ who I also hope to see, & to have the pleasure of showing him a few of my Eastern Gems.

Wishing you health & strength to make known your rich collections & careful observations to the world, (a task in which I soon trust to be myself labouring)[.]

I remain | Yours very sincerely | Alfred R. Wallace [signature]

H W. Bates Esq.

I should not wonder that your paper will convert Hewitson.²² He is not I think very susceptible to general arguments, but this will come home to his very bosom & touch his feelings if anything will!! I hope you have sent Darwin²³ a copy I am sure it would please him[.]²⁴

P.S. I quite agree with you as to the affinity of the Crassus²⁵ group with Ornithoptera,—²⁶ a note to the same effect has stood in my "Boisduval"²⁷ for years. I doubt however the propriety of placing Dolicaon²⁸ &c. with Protesilaus.²⁹ I am now anxious to compare the Eastern forest group Polydorus³⁰ &c. with Aeneas,³¹ to see if there is affinity of structure.³²