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Darwin Correspondence Project

To Roland Trimen   27 March [1868]1

4 Chester Place | N.W.

March 27th

(Excuse this paper)

My dear Mr. Trimen

Your letter is of much value to me, for I shd. have made a terrible mistake, if I had said no moths were more finely coloured beneath than above.—2

Do you think I might say as follows,—after speaking of brilliant under surface of several Butterflies.— Moths do not hold when at rest their wings vertically—the under surface rarely more brightly-coloured than upper surface—but exceptions occur, Mr T. informs me from Guenée of 3 moths—(here describe briefly Gastrophora), in which under surface much the most brilliant.—But these are exotic moths & it is not known whether their habits would throw any light on their colouring— Mr T. also informs me that the lower surface of the wings in certain other Geometræ & quadrifid Noctuæ are either more variegated or more brightly, coloured than the upper surface; but some of these species have the habit of “holding their wings quite erect over their backs, retaining them in that position for a considerable time” so that the under surface wd be exposed

Other species “when settled on the ground or herbage have the habit of now & then suddenly lifting up the wings slightly so as to afford a glimpse of the bright colouring of the abdomen & underside”.— Hence the circumstance of under side of the wings in certain moths being more brightly coloured than the upper, is not so anomalous in reference to our present point of view as it at first appears.—3

It is a horrid shame to trouble you, but wd you return these remarks, which will serve as memorandum for me, (written currente calamo),4 & just tell me in half a dozen words, at foot, whether what you have told me justifies what I say.— I will modify to any extent or if you think I have written too strongly strike all out.—

That is a most doubtful & difficult point about females “being provided with special ornaments to attract the males”, on account of eagerness of males for any females.—5

Yours most truly obliged | C. Darwin—


The year is established by the relationship between this letter and the letter from Roland Trimen, 26 March 1868.
See letter from Roland Trimen, 26 March 1868. See Descent 1: 397–8 for the published version of these remarks, which is very similar.
Currente calamo: as the pen runs; in haste (Latin).
See letter from Roland Trimen, 26 March 1868. In Descent 1: 401, CD concluded that he had no reason to suspect, with either butterflies or moths, that males were attracted by the beauty of the females. He accounted for rare cases of the female being more beautiful than the male as a consequence of mimicry.


Thanks RT for letter which saves him from a "terrible mistake": that no moths were more brilliantly coloured beneath than above. Suggests revised version for comment. [See Descent 1: 397.]

Letter details

Letter no.
Charles Robert Darwin
Roland Trimen
Sent from
London, Chester Place, 4
Source of text
DAR 82: A119–20
Physical description
4pp †

Please cite as

Darwin Correspondence Project, “Letter no. 6060,” accessed on 20 April 2019,

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