From H. W. Bates   [1 December] 18611

King St. Leicester

31 Novem 1861

My Dear Sir

The following are the references which I promised.2

Volucella bombylans

V. bombylans (red-tipped abdomen)

V. plumata (Meigen) (= mystacea Fab) (white-tipped abdomen)

M. Macquart (Hist. Nat. des Diptères Vol. 1 1834, p 494) places both together, terming V. plumata “variété constante” of V. bombylans.3 at p 479 he quotes M. de St Fargeau who observed the accouplement of the two forms:4 and stated moreover that the two other European Volucellæ also had each a constant variety. A kind of Dimorphism?

Zeller (Entom. Zeitung, 1842 p 65) confirms the above statement from personal observation, as to V. bomb. & V. plumata.5

Erichson (Entom. Zeitung 1842 p 113) described all the known varieties of the species.6 They were then 7—No 1 being the true bombylans which passed gradually into plumata through V. hæmorrhoidalis (Zetterstedt) and others.

On the meaning of the colours and markings of butterflies’ wings. The article on the subject which I mentioned to you is by Dr. Rössler in the Wiener Entomologische Monatschrift 1861 p 163.7 On reading it through carefully I find many interesting facts, which I should have done well to quote in my paper but I wrote it before Dr. R’s was published. He says plainly that the colours & markings are given to deceive the enemies of the species. All the facts are from European insects. He is wrong in saying that “it is a general law that animals are clothed in the colours of their resting places.” This is a kind of mistake which we are all apt to fall into.

I think the whole tenour of your book teaches what I carefully insisted on in my paper that the welfare of species is the object of all structures & forms. All species exist by virtue of some endowment enabling them to withstand adverse circumstances. If an exact mimetic dress be not required to enable a species to maintain itself, the causes which tend to produce it will not operate. There are species of the same genus of similar habits & living on the same soil; one of which is of the colour of the soil and another of a completely contrasted colour. Therefore it is not a general law that a parasitic species shall mimic its victim &c &c.   the mimicry is only part of the wider law above mentioned & the exceptions are proved as they ought to be by the same wider law.

Dr Rossler remarks that the underside of the Vanessa & other butterflies are coloured to resemble the bark of trees; because as they close the wings when they alight, they become suddenly invisible. In moths (Noctuæ) which rest with wings deflexed the upper covering the lower it is the upper surface of the upper wing only which imitates bark. I will mention that in some of these moths (Catocala) the underwings are of brilliant colours; So that here we have a double dress answering two purposes in the welfare of the species. The high colour being explicable by sexual selection & the plain colour by the check caused by insectivorous animals.

The essay of Burmeister’s which I mentioned as probably worth reading is called Vergangenheit & Gegenwart des Thierreichs8

incomplete

CD annotations

6.1 Dr … invisible. 6.3] scored red crayon
6.4 the upper covering … bark. 6.5] scored red crayon
6.6 So … animals. 6.8] scored red crayon
7.1 The … Thierreichs 7.2] ‘Showing earlier form general, later specialised.’ added pencil
On cover: ‘Mr Bates | References on Dimorphism of Volucella— on Mimetic resemblance— ; ’Colours of *lower surface of wing [interl, del pencil] Butterflies & Moths— Sexual Selection‘ ink, del pencil; Reference to Burmeister on specialisation’ ink; ‘On under surface of wings of Vanessae like bark | On upper surface of cut [interl] wings of Moth like bark— Lower wings brightly coloured (Red underwings Weir9—’ ink, del pencil; ‘Selection’ brown crayon, del pencil

CD note:10

Nov. 22d. 1861. Mr Bates showed me the 2 Volucellas like B. hortensis & lapidarius.— in B. Mus they are marked as distinct species; but Erichson says they blend together on continent, though distinct in England— F. Smith has bred them [‘here’ del] one from here & has not seen variations—11 In Amazonia there is one jet black H. Bee & one parasitic Bee *not Apathic [interl], in same region also jet black. In England some Apathic very like the Humbles they frequent—other parasitic Bees not like.—but then close resemblance not necessary, for stronger Humble-bees will take up residence occasionally with distinct species.— F. Smith showed me a brownish Volucella always parasitic in Brown Humble-bees nests.— The volucella very good case in all ways.— I saw the mimetic [interl] Butterflies wonderful. wonderful—

1
The date of this letter has been given as 1 December since there are only thirty days in November.
2
Bates had shown CD his collection of South American insects, which was being exhibited at the British Museum, during CD’s recent visit to London (see CD note). CD’s visit to the British Museum is also mentioned in the letter to J. D. Hooker, 25 November [1861].
3
Macquart 1834–5.
4
Amédée Louis Michel Lepeletier de St Fargeau was a noted French entomologist.
5
Zeller 1842.
6
Erichson 1842.
7
Rössler 1861.
8
The publication details of the essay by the German naturalist Karl Hermann Konrad Burmeister have not been traced.
9
It is possible that CD made some of the cover annotations several years after he received the letter, during his preparation of Descent, in which there is a chapter on sexual selection in butterflies and moths (Descent 1: 386–417). The naturalist John Jenner Weir mentioned the brightly coloured underwings and dull upperwings of certain Lepidoptera in Weir 1869–70, p. 22. CD cited Weir’s article in Descent 1: 395 and 417.
10
The note is associated with the letter in DAR 205.10 (Letters).
11
CD refers to the German entomologist Wilhelm Ferdinand Erichson and to Frederick Smith, an entomologist employed in the zoological department of the British Museum.

Please cite as “DCP-LETT-3336,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-3336