The Naturalist on the River Amazons

Mr. Wallace’s letter is of interest as dealing with the Guiana region as a centre of distribution:— )

Myr. A. R. Wallace to H. W. Bates.

‘ LOBO RAMAN, 100 MILES E. OF BENCOOLEN,*

‘« December toth, 1861.

‘““MyY DEAR BATES,

‘‘T should have written to you before to thank you for your paper on the ‘PaZgzizos,’ but 1 somehow never can post up my correspondence till I get into some savage wilderness like that in which I am at present. I have read your paper with great attention, and 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 simplicity and beauty of the Darwinian philosophy. ‘Your paper is in every respect an admirable one, and incontestably proves the necessity of minute and exact observation over a wide extent of country to enable a man to grapple with the more difficult groups, unravel their synomy, and mark out the limits of the several species and varieties.

All this you have done, and have besides established a very interesting fact in zoological geography,—that of the southern bank of the river having received its fauna from Guyana, and not from Brazil. There is, however, another fact I think of equal interest and importance, which you have barely

touched upon, and yet I think your own materials in this very paper establish it, viz.: that the river, ina great many cases, limits the range of species, or of well-marked varieties.... In mammals this fact was not so much to be wondered at, but few persons would credit that it would extend to birds and winged insects.... It would seem that Guyana forms having once crossed the river, have a great tendency to become modified, and then never recross. Why the Brazilian species should not first have taken possession of their own side of the river is the mystery. I should be inclined to think that the river bed is comparatively new, and that the south plains were once continuous with Guyana; in fact that Guyana is olderthan North Brazil, and after it had pushed out its alluvial plains into what is now North Brazil, an elevation on the Brazilian side made the river cut a new channel to the northward, leaving the Guyana species isolated, exposed to competition with a new set of species, and thus led to their becoming modified as we now findthem. The phenomenon of a tract of country having been peopled from one now separated from it, and not from that of which it forms a part, is too extraordinary not to require some special and extraordinary cause, and the one I have mentioned seems capable of producing the effects, and by no means improbable (however unexpected) in itself.... ‘‘T suppose you will turn now to the Coleoptera, and give us the Cicindelid@@ on the same plan.... ‘‘ Yours very sincerely,

*‘ALFRED R. WALLACE.”’

But for Darwin’s persistent urgency, it is probable that the delightful narrative of Bates’s Wanderjahre would not have been written. The following letters—notably that from Bates given on p. lxiii—go to prove this, and, moreover, are of interest as showing how high an estimate of Bates was formed by Darwin even before their personal intercourse began.

Charles Darwin to H. W. Bates.

‘“‘DOowN, BROMLEY, KENT, AZrél 4th, 1860.

**“My DEAR SIR,

‘‘T have been unwell, so have delayed thanking you for your admirable letter.* I hope you will not think me presumptuous in saying how much I have been struck with your varied knowledge, and with the decisive manner in which you bring it to bear on each point—a rare and most high quality, as far as my experience goes. I cannot hope you will find time to publish largely; before the Linnean Society you might bring boldly out your views on species. ‘‘ Have you ever thought of publishing your travels and working in them the less abstruse parts of your natural history? You must also have seena

• The absence of this and other letters from Bates to which reference is made, is due, as Mr. Francis Darwin informs me, to Mr. Darwin having destroyed all his correspondence dated prior to 1862.

good deal of the natives. I know well it would be quite unreasonable to ask for any further information from you; but I will just mention that I am now, and shall be for a long time, writing on domestic varieties of all animals. Any facts would be useful; especially any showing that savages take any care in breeding their animals; or in rejecting the bad and preserving the good. I have already collected much on this head, but am greedy for facts. You will at once see their bearing on variation under domestication.... Hardly anything in your letter has pleased me more than about sexual selection. In my larger MS. (and indeed in Orzgiz with respect to tuft of hairs on breast of cock turkey) I have guarded myself against going too far; but I did not at all know that male and female butterflies haunted rather different sites. If I had to cut up myself in a review, I would have quizzed Sexual Selection; therefore, though I am fully convinced that it is largely true, you may imagine how pleased I am at what you say in your belief, This part of your letter is to me a quintessence of richness. The fact about butterflies attracted by coloured sepals is another good fact—worth its weight in gold. It would have delighted the heart of old Christian C. Sprengel, now many years in his grave. ‘‘T am glad to hear that you have specially attended to ‘ mimetic’ analogies—a mos¢ curious subject. I hope you will publish on it. I have for a long time wished to know whether what Dr. Collingwood asserts is true, that the most striking cases generally occur between insects zzhabiting the same country. ** Yours most truly obliged, “C. DARWIN.”

*‘ Down, September 25th, 1860. “‘Your letter, like every one that I have received from you, has been a mine of wealth, and has interested me greatly. But first for the more important point, viz., your Book of Travels, and I heartily rejoice that you intend publishing. I should think that you could not have a more respectable or pleasanter publisher than Mr. Van Voorst. At the same time I apprehend there can be no doubt that Murray has much greater power of getting large distribution. Murray has the character of being a very liberal paymaster, and I am sure I have found him most liberal and pleasant to deal with.... I rejoice I went to him with the Ovigzz. By the way, here is a case in point! Colburn did not value my Yournal of Researches, and would never, I am sure, have published a second edition. I took it from him and sold it to Murray, and it has long and gveat sale up to present day. If you should decide on Mr. Murray, and if you would so like, I shall be most happy to write to him, and can most truly tell him how much I appreciate the force of intellect and knowledge and style of your lettersto me.” (Then follows advice asto striking out superfluous words, already extracted from this letter, and printed in Darwin's Zzfe, vol. ii., p. 380.) ‘‘ What a capital paper yours will be on mimetic resemblances. You will make quite a new subject of it.... What wonderful cases yours seem to be. “Yours sincerely,

“¢C. DARWIN.’”

In January 1861 Bates married a young lady for whom he had kept a tender place in his heart during his long absence— Miss Sarah Ann Mason, of Leicester, by whom he had three sons and two daughters. Darwin writes to congratulate him and to hope that he “may succeed, for the sake of science, in getting fixed near London.” Meanwhile, he was hard at work over his book, writing and re-writing the earlier chapters—some of them being recast three and four times before his severe judgment was satisfied. “What takes me one day to write takes five to alter,” he says in one of hisletters. Darwin, who generously spared time to read the manuscript, writes under date January 13th, 1861:—

‘‘T have been very bad for a fortnight, and could not read your MS. before to-day and yesterday. It is, in my opinion, excellent—style perfect, description first-rate (I quite enjoyed rambling in forests), and good dashes of original reflexions.... I feel assured that your book will be a permanently good one, and that your friends will always feel a satisfaction at its publication. I will write when you like to Murray.’’

Concurrently with this, Bates wrote his celebrated paper on “Mimicry,’ * which is his distinctive contribution to the theory of natural selection. The observations which led him to the explanation of those curious phenomena known as “mimetic analogies” were made upon insects, which group supplies by far the larger mass of evidence. In looking for hints of these observations during his travels, one is found in a letter from St. Paulo, September 5th, 1858, printed in the Zoologzst, vol. xvi., pp. 6165-6:—

‘In the shady ravines of the forest, many species of Ithomiz were found in greater or less abundance.... Flying amongst the Ithomiz was now and then to be observed a Leptalis; I was very careful to secure every specimen. and the gathered series, now I come to examine them closely, have interested me as much as any other acquisition made during my excursion. Abstraction made of a white species and the Vocula, the rest may be considered either as six species allied to L. Lysinoé (fewz¢s.), or as the latter branching out into six rather widely differing varieties. In either case they are very interesting, because some of the kinds come to imitate each a species of Ithomia, common only in this locality. It would seem then almost correct to say that at Ega and other stations these new Leptales are not found, because the {[thomia to which they correspond are also absent. L. Lysinoé imitates Ithomia Flora; but three at least of the new species imitate three of the

• This term has been chosen by biologists merely for convenience, and not as implying conscious or voluntary imitation on the part of the mimicking species,

commonest Ithomia of St. Paulo; on the wing their resemblance is much more striking than when in the cabinet. In fact I was quite unable to distinguish them on the wing; and always on capturing what I took for an Ithomia and found when in the net to be a Leptalis mimicking it, I could scarcely restrain an exclamation of surprise. One species imitates exactly I. Cidonia, another I. Onega, which is more abundant at St. Paulo than at any other place, and a third another unnamed species of Ithomia, also one of the most abundant species. The resemblance between Leptales and Ithomiz, two groups of Diurnes much more widely separated than they appear in our classifications, is repeated in the case of a group of Bombycide moths, of which there are at least two genera imitating the Ithomiz and the larger Heliconiz. One of them, which I saw first at the British Museum, exactly imitates Ithomia Flora; at Ega there is one imitating in the same way Ithomia Fluonia of the same locality. At Fonte Boa appears another, standing in the same relation to I, Ailia of the same place, and at St. Paulo there are others occurring simultaneously with the peculiar Ithomiz of the district. These analogies to me appear amongst the most beautiful phenomena in nature.”’

The full title of the paper is “ Contributions to an Insect Fauna of the Amazon Valley. Lepidoptera: Heliconide.” By Henry Walter Bates, Esq. (Communicated by the Secretary.) Read November 2Ist, 1861.* The interesting and important character of the phenomena described in the paper, and the relatively small space given to them in the Naturalist on the Amazons, may render some account of the matter not out of place here; the more so as the paper itself is buried in the well-nigh inaccessible memoirs of a learned society. The literature of the subject which has followed the publication of that paper is too extensive to be touched upon here. After describing the natural history of the Heliconide, a family of brilliantly-coloured butterflies which abound in the American tropics, Bates referred to the mimicking of which a large number of species are the objects. “Mimetic analogies, it is scarcely necessary to observe, are resemblances in external appearance, shapes, and colours between members of widely distinct families; an idea of what is meant may be formed by supposing a pigeon to exist with the general figure and plumage of a hawk.’ t