Darwin Correspondence Project

King St   Leicester

30 Sept. 1861

My Dear Sir

Before you go to the B.M. to inspect the Volucellæ flies I wish to give you more exact information about them. The species which resembles Humble bees is the Volucella bombylans (authors) and the constant variety is V. plumata (Meigen) (= V. mystacea Fabr.)— One of these resembles Bombus lapidarius, the other B. terrestris.— These are the only two varieties found in this neighbourhood and until recently the only two described. They were always considered as distinct species until Lepelletier de St Fargeau observed them to copulate,— they are not the sexes, however;—as there are males & females in each form. The female lays its eggs & the larvæ are bred on the nests of Humble bees.—

It has been lately shown that these two forms are united by a series of varieties or connecting links to the number of five; one of which V. hæmorrhoidalis (Zetterstedt) has been described as a distinct species. They are found on the continent but I believe they are not found in all localities together with the two chief forms. I have never observed them.

Another species of Volucella, V. inanis resembles a wasp; its ova & larvæ are found in wasps' nests.—

A third common species is V. pellucens   this in its dress is entirely unlike either of the other two species. I cannot find any account of its larva. It would be interesting to know whether it is parasitic also. The perfect insect has not the slightest resemblance to a Hymenopterous insect, but is of the same general appearance as the bulk of the Volucellæ species of which I took many in S. America.

It would appear then that V. pellucens retains the facies of its genus, but that the other two have been widely diverted in this respect from their normal type, in strict connection with their habit of depositing their ova in the nests of wasps and Bombi. It is not necessary to explain to you that I mean—the adult insects being exposed to the attacks of the Bombi near their nests,—their resemblance is explicable on the theory of Nat. Selection.

Precisely the same phenomenon occurs in genera of butterflies in S. America where some species wear the dress of species belonging to widely different families. But here the object of the analogical resemblance is different. Here it is because the one set of species is exposed in the adult state to a persecution by insect enemies from which the other set is free.

This entire class of facts is extremely numerous in insects. But they are very complex. It requires the most subtle & flexible nature of mind to understand & explain them. But whilst they are unexplained on the rational theory, they remain one of the strongest arguments to the believers in the miraculous in creation.

Dr Collingwood's paper ``on recurrent animal forms'' does not touch this class of facts, either in description or explanation. All that he can say is that similar habits &c will produce analogical resemblance between species belonging to widely different families. But ours are not general resemblances   they are close specific resemblances as far as external appearance is concerned. But, as I have shown in the paper I mentioned to you,—the causes which produce close specific resemblances do not & cannot operate except in those forms which are already made generally similar by the operation of other causes.

I am extremely obliged to you for your advice regarding my proposed book. It will be very useful to me. It was quite new to me that I could agree with a publisher to sell him only the 1st edition. I shall find it very difficult, I am afraid, to write in a simple style. I have begun to try to write a chapter or two—but I find it very perplexing, in the mass of details contained in my journals, to select what would be likely to be most interesting to the public. It will never do, I think to narrate even the chief events consecutively of 11 years travel & residence. I went backwards & forwards. In your voyage there was something similar; & I shall try to work mine into a compact whole but can never imitate the wonderful art you have shown in doing so. When I have finished a chapter or two I will apply to Murray & then shall feel much obliged to you if you would write him a word or two by way of introduction.

Yours sincerely | H W Bates