Ɛpsilon

From Raphael Meldola   24 March 1873

21 John Street, | Bedford Row, W.C.

March 24th. 1873

Dear Sir,

At a meeting of the Entomological Society last Monday evening Mr. Bates put your questions on ocelli to the Members present.1

I looked through my collection of butterflies to-day to see if any difference existed in the ocelli of the two sexes of any species possessing this marking. The only difference I could find was in our common Satyrus Tithonus.2 The ocellus in this species consists of a black spot with two central white dots. In the ♂ the dots are situated one beneath the other thus

diagram

In the ♀ the dots are much more obliquely placed—

diagram

The difference is a trifling one but so far as I know has not been observed before. It is moreover a constant sexual character in all specimens that have come under my notice.

My time is so much engaged at present that my researches in mimetic analogy & protective resemblance progress but slowly. The results I have arrived at I propose to publish in a series of papers. The first instalment will appear in the next part of the Proc. Zoo. Soc.3

I must apologise for troubling you with so small a matter but every natural fact has a meaning for those who can & will decipher it.

Yours respectfully, | R. Meldola.

C. Darwin Esq. M.A, F.R.S.

P.S. I notice with pleasure the recent influx of papers on subjects connected with evolution to the Royal Society.

CD annotations

2.2 The only … Tithonus. 2.3] double scored pencil
Top of letter: ‘Descent of Man’ pencil, circled pencil; ‘Ocelli’ red crayon
1
At a meeting of the Entomological Society of London on 17 March 1873, the vice-president, Henry Walter Bates, asked on CD’s behalf for information on ‘sexual differences in insects furnished with ocellated spots’ (Proceedings of the Entomological Society of London (1873): xiii). In Descent 2d ed., CD expanded his discussion of the extreme variability of the ocelli on the wings of Lepidoptera, admitting that the presence of so ornamental a feature in both sexes was a problem for the theory of sexual selection; he referred to information received in response to this request although he did not name Meldola (Descent 2d ed., p. 320 and n. 25).
2
Satyrus tithonus is a synonym of Pyronia tithonus (the gatekeeper butterfly).
3
Meldola had read a paper on variable protective colouring in insects at the Zoological Society of London in February 1873; it was published later in the year (Meldola 1873). No further parts were published. For CD and Meldola’s earlier correspondence on the subject, see Correspondence vol. 20.

Please cite as “DCP-LETT-8821,” in Ɛpsilon: The Charles Darwin Collection accessed on 5 June 2025, https://epsilon.ac.uk/view/dcp-data/letters/DCP-LETT-8821