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.
Itajahy, Sa Catharina, Brazil
January 16. 1872.
My dear Sir.
I must beg your pardon for having delayed so long answering yourkind letter of Aug. 2d and expressing my cordial thanks for yourhaving sent me a copy of Mr. Chauncey Wright’s very able refutation ofMr. Mivart’s “Genesis of species”.—f1 But I have been away from myhome for about five weeks on an excursion through the northern part ofour province.f2
The yellow, white and red Hedychium, mentioned in a former letter,are, as you suppose, distinct species.f3
I have no objection to your alluding to my idea of sexual selectionhaving come into play in the case of mimetic butterflies.f4 I may heremention a curious fact relating to the same subject, which I observeda fortnight ago. On an excursion, which I made with a friend of mine,we saw two similarly coloured butterflies playing together, whirlinground and pursuing each other for a considerable time. At last wesucceeded in catching both of them and found, to your great surprise,that they belonged to two widely different species. I had caught thevery common Agraulis Juno Cr. and my friend the rare MarpesiaPetreus Cr.—f5 The shape of the wings and the distribution of thecolours is so different and the two butterflies were so close togetherfor a long time, that they could hardly have mistaken each other forspecimens of their own species. Apparently they were playing togetheronly in order to behold and admire each other. Unfortunately I forgotto ascertain the sex of the two specimens.—
On the same occasion we observed three species of the curious genusCastnia, one of them (A.) being extremely frequent. The hind-wingsin two of these species had dull colours; and in these, when at rest,the hind-wings were always overlapped and concealed by thefront-wings. In the third species (B)
the black-hind-wings werespotted with red and white, and this species, when at rest, expandedtheir wings horizontally, so that the hind-wings were fully exposed toview.— You know, that the Castniæ fly about, with great rapidity,during the day.—
I have of late been attending to our Termites. They are verycurious animals and the several species differ much in theirhabits. The most interesting fact, I hitherto observed, is theexistence, in some species of Calotermes, of larvæ provided withwing-like horizontally expanded processes on the prothorax andmesothorax.— 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 toso enormous a volume, as they do in the genus Termes. All this seemsto prove, that they are a more primitive form of the family. Andindeed, according to Hagen, the oldest fossil remains of Termites(Calotermes Heerii) appear to belong to that genus, which is perhapsthe oldest of all now living genera of insects.f9 The young larvæprovided with the curious processes live under exactly the sameconditions with the older ones, in which these processes havedisappeared, while the rudiments of the wings make their appearance onthe mesothorax and metathorax, and thus it is not probable, that theyshould have acquired the processes by natural selection; it appears tobe more probable, that they inherited them from a very remoteancestor, which in its adult state may have resembled theselarvæ. In this case the Calotermes-larvæ might be the oldest ofall known forms of insects.—
You know, that some ants (Odontomachus) use their long mandibles formaking most surprising jumps in a backward direction.f10 Is it not acurious coincidence, that the soldiers of some Termites have the samehabit of leaping backward with the aid of their mandibles? Theseleaping soldiers have been described and figured by Hagen under thename of Termes cingulatus, but I have some doubts, whether theyreally belong to that genus.f11 Linné already knew the leaping ofTermites, for he says of his T. fatale: “maxillis longis altissimeresiliens”;f12 but no subsequent observer appears to have seen it.—
Have you already seen the Dentalium-like cases of one of ourcaddish-worms, (Leptocerus(?) Grumicha Vall.)?f13 They show, that theremay exist strange resemblances even without mimicry or analogousvariation.
I hope, dear Sir, that this letter will find you in good health andam, as always, with sincere respect | Yours very faithfully | FritzMüller.