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Darwin Correspondence Project

From Roland Trimen   13 April 1868

71, Guildford Street | Russell Square | London, W.C.

13th. April, 1868.

My dear Mr. Darwin,

In the accompanying extract you will see that Blanchard records an Australian case fully as remarkable as that of our Lasiocampa Quercus, but unfortunately does not give the name of the species.1 He implies a doubt whether acuteness of smell can be taken as an explanation of these cases; but my own experience of the ♂s of Quercus besieging me, when I had only about me the empty box in which a female had been the previous day, makes me think that an odour must be the attracting power. What he says about the males in these cases being always species with pectinated or branched antennæ is worth notice; because Réaumur and others have contended that the sense of smell resides in those organs.2

I enclose a photograph more like me than the old one in your book.3 It is almost too bad to ask for a recent one of yourself, considering how you must be plagued with applications from all quarters, but I shall be grateful if you have one to spare, as that which you sent to me at the Cape does not much remind me of you.4

I leave for Cape Town on 8th. May.

Believe me | Very faithfully yours, | Roland Trimen


Extract from Emile Blanchard’s “Métamorphoses Mœurs, et Instincts des Insectes”, (Paris, 1868.) pp. 225–26.5

“Chez le plus grand nombre des Bombyx, on constate toujours avec surprise une étrange faculté dont on a peu d’exemples. Les mâles sont attirés par des femelles de leur espèce à d’énormes distances. Une femelle est-elle emportée dans une maison, à l’intérieur d’une ville, loin de toute végétation et placée sur une fenêtre, même à un étage élevé, il est ordinaire que dans la soirée, des mâles arrivent en grand nombre autour de cette femelle, souvent après s’être heurtés aux murailles, aux fenêtres, à tous les obstacles, car la vue ne les dirige en aucune façon.

M. Jules Verreaux, dont les voyages ont été extrêmement profitables aux sciences naturelles, nous a rapporté qu’étant en Australie, il lui arriva un jour de saisir une femelle d’une petite espèce de Bombyx, et de l’emprisonner dans une boite. La boite mise dans la poche, il continua son excursion; des mâles de la même espèce ne cessèrent de voltiger autour de lui, et quand il rentra dans sa demeure, deux cents Papillons l’y suivirent. On a cherché à expliquer cette faculté des Bombycides par la subtilité de l’odorat, mais il nous est difficile de comprendre qu’une odeur insaisissable pour nos sens puisse être reconnue à la distance de plusieurs kilomètres. Nous remarquons seulement ce qui semble n’avoir jamais remarqué, que les Lepidoptères mâles attirés de loin par leurs femelles, Bombycides et Phalénites, ont tous des antennes rameuses. Il y a au moins un indice dans cette coincidence; peut-être une étude approfondie de la structure des antennes de ces insectes fournira-t-elle une révélation.”

p. 282.6

“Ces Lepidoptères”—(Phalénides ou Geometræ)—“ne sont pas sans analogie avec les Bombycides: de même que parmi ces derniers, il en est dont les femelles sont privées d’ailes ou n’en ont que des rudiments; il est aussi une infinité de mâles dont les antennes pectinées ou plumeuses ont l’aspect de véritables panaches.

Les Phalénides mâles étant comme les Bombyx attirés de fort loin par leurs femelles, il y a une double coïncidence nous donnant à penser que le grand developpement des antennes a réellement un rapport avec l’aptitude singulière de beaucoup de Bombycides et de Phalénides.”

CD annotations

1.1 In … power. 1.6] crossed pencil
1.8 because … May. 3.1] crossed pencil
3.4 des mâles … suivirent. 3.6] scored red crayon, double scored blue crayon, double scored pencil
3.5 deux … suivirent. 3.6] underl red crayon
3.7 mais … kilomètres. 3.8] scored blue crayon, ‘!!’ added blue crayon


Trimen refers to Emile Blanchard and Blanchard 1868. For earlier references to the behaviour of the moth Lasiocampa quercus (the oak eggar), see the letter from Roland Trimen, 20 February 1868, the letter to H. T. Stainton, 21 February [1868], and the letter from J. J. Weir, [before 3] March 1868.
René Antoine Ferchault de Réaumur had suggested that olfaction could be one of the functions of antennae in moths (Réaumur 1734–42, 1: 224).
The photograph has not been found. From 1865, CD kept a ‘Scientific Album’ of photographs but it has not been found in the Darwin Archive–CUL or at Down House (see Correspondence vol. 13, letter to A. R. Wallace, 1 February [1865]).
Trimen possessed an earlier photograph of CD, without a beard, sent in 1863 (see Correspondence vol. 11, letter to Roland Trimen, 23 May [1863] and n. 3).
Aside from minor misspellings, Trimen transcribed the extracts accurately. English translation of extract from Blanchard 1868, pp. 225–6: In the majority of Bombyx, one notes, always with surprise, a strange faculty of which few examples are known. The males are attracted by females of their species over vast distances. Should one female be carried into a house in a town, far from any vegetation, and placed on a window, even on an upper storey, it is usual for males to appear in great numbers around the female during the evening, often after having flown into walls, windows, and all kinds of obstacles, because they are not guided by vision in any way. M. Jules Verreaux, whose travels have been extremely profitable to the natural sciences, has related to us that whilst in Australia he one day succeeded in capturing a female of a small species of Bombyx, and in imprisoning her in a box. With the box placed in his pocket, he continued his excursion; males of the same species fluttered around him incessantly, and when he went back into his abode, two hundred Butterflies followed him in. One has attempted to explain this faculty of the Bombycides by recourse to the subtlety of their sense of smell, but it is hard for us to understand how an odour which our senses cannot grasp could be recognised several kilometres away. We shall only note something that never seems to have been noted before, that the male Lepidoptera attracted from a distance by their females, Bombycides and Phalenites, all have branching antennae. There is something significant, to say the least, in this coincidence; perhaps a deeper study of the structure of the antennae of these insects would offer a revelation. In Blanchard’s usage, Bombyx and ‘Bombicide’ evidently refer to any type of silk moth (superfamily Bombycoidea, in modern taxonomy), while ‘Phalenite’ would be roughly equivalent to the Geometrae of English authors (or the modern superfamily Geometroidea; see letter from Roland Trimen, 26 March 1868 and n. 3). In Descent 1: 312, CD referred to Verreaux’s experiment and cited Blanchard 1868, pp. 225–6.
English translation of extract from Blanchard 1868, pp. 282: “These Lepidoptera”—(Phalenides or Geometrae)—“are not lacking in analogy with the Bombycides: just as among the latter, there are some whose females are deprived of wings or only have the rudiments thereof, there is also an infinity of males whose pectinate or feathery antennae have the aspect of true plumes. The male Phalenides, being, like Bombyx, attracted from a great distance by their females, there is a double coincidence, which leads us to think that the great development of the antennae truly has a relation with the singular aptitude of many Bombycides and Phalenides.”


Extract from Émile Blanchard’s Metamorphoses, moeurs et instincts des insectes [1868], on attraction of males by female Lepidoptera, and possible explanation.

Letter details

Letter no.
Roland Trimen
Charles Robert Darwin
Sent from
London, Guildford St, 71
Source of text
DAR 85: B50–1
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 6116,” accessed on 25 June 2019,

Also published in The Correspondence of Charles Darwin, vol. 16