From Fritz Müller 16 January 1872
Itajahy, Sa Catharina, Brazil
January 16. 1872.
My dear Sir.
I must beg your pardon for having delayed so long answering your kind letter of Aug. 2d and expressing my cordial thanks for your having sent me a copy of Mr. Chauncey Wright’s very able refutation of Mr. Mivart’s “Genesis of species”.—1 But I have been away from my home for about five weeks on an excursion through the northern part of our province.2
The yellow, white and red Hedychium, mentioned in a former letter, are, as you suppose, distinct species.3
I have no objection to your alluding to my idea of sexual selection having come into play in the case of mimetic butterflies.4 I may here mention a curious fact relating to the same subject, which I observed a fortnight ago. On an excursion, which I made with a friend of mine, we saw two similarly coloured butterflies playing together, whirling round and pursuing each other for a considerable time. At last we succeeded in catching both of them and found, to your great surprise, that they belonged to two widely different species. I had caught the very common Agraulis Juno Cr. and my friend the rare Marpesia Petreus Cr.—5 The shape of the wings and the distribution of the colours is so different and the two butterflies were so close together for a long time, that they could hardly have mistaken each other for specimens of their own species. Apparently they were playing together only in order to behold and admire each other. Unfortunately I forgot to ascertain the sex of the two specimens.—
On the same occasion we observed three species of the curious genus Castnia, one of them (A.) being extremely frequent. The hind-wings in two of these species had dull colours; and in these, when at rest, the hind-wings were always overlapped and concealed by the front-wings. In the third species (B)
the black-hind-wings were spotted with red and white, and this species, when at rest, expanded their wings horizontally, so that the hind-wings were fully exposed to view.— You know, that the Castniæ fly about, with great rapidity, during the day.—
I have of late been attending to our Termites. They are very curious animals and the several species differ much in their habits. The most interesting fact, I hitherto observed, is the existence, in some species of Calotermes, of larvæ provided with wing-like horizontally expanded processes on the prothorax and mesothorax.— The species
of Calotermes do not build nests; they have but one form of neuters (soldiers, but no labourers); the fertilized females do not swell to so enormous a volume, as they do in the genus Termes. All this seems to prove, that they are a more primitive form of the family. And indeed, according to Hagen, the oldest fossil remains of Termites (Calotermes Heerii) appear to belong to that genus, which is perhaps the oldest of all now living genera of insects.9 The young larvæ provided with the curious processes live under exactly the same conditions with the older ones, in which these processes have disappeared, while the rudiments of the wings make their appearance on the mesothorax and metathorax, and thus it is not probable, that they should have acquired the processes by natural selection; it appears to be more probable, that they inherited them from a very remote ancestor, which in its adult state may have resembled these larvæ. In this case the Calotermes-larvæ might be the oldest of all known forms of insects.—
You know, that some ants (Odontomachus) use their long mandibles for making most surprising jumps in a backward direction.10 Is it not a curious coincidence, that the soldiers of some Termites have the same habit of leaping backward with the aid of their mandibles? These leaping soldiers have been described and figured by Hagen under the name of Termes cingulatus, but I have some doubts, whether they really belong to that genus.11 Linné already knew the leaping of Termites, for he says of his T. fatale: “maxillis longis altissime resiliens”;12 but no subsequent observer appears to have seen it.—
Have you already seen the Dentalium-like cases of one of our caddish-worms, (Leptocerus(?) Grumicha Vall.)?13 They show, that there may exist strange resemblances even without mimicry or analogous variation.
I hope, dear Sir, that this letter will find you in good health and am, as always, with sincere respect | Yours very faithfully | Fritz Müller.
Has no objection to CD’s alluding to FM’s idea that sexual selection has come into play in mimetic butterflies.
Reports observations on other butterflies and on termites.
Please cite as
Darwin Correspondence Project, “Letter no. 8161,” accessed on 21 February 2017, http://www.darwinproject.ac.uk/DCP-LETT-8161