From Roland Trimen   31 December 1867

My dear M^r. Darwin,

In a wilderness of ocelli,¹ I have stupidly forgotten the exact nature of the information which you indicated as requisite. Am I right in thinking that you wanted one or two instances of gradation in the developement of ocellated spots in the same species? or, if that cannot be found, of gradations from a simple spot to a many-ringed ocellus in closely-allied species?²

With reference to the relative abundance of the sexes, which is apparently very generally in favour of the ♂ in butterflies, I find that Wallace (Trans. Linn. Soc. XXV “On the Papilionidæ of the Malayan Region”) notes that the ♀s of Ornithoptera Crœsus (peculiar to the island of Batchian) were “more plentiful” than the ♂s.³ This is a case in which there is a very wide difference between the sexes, the ♂ being splendidly coloured with shifting green and orange on a black ground, while the ♀ is (like those of all the nearly-allied species) dull-brown with whitish markings.

M^r. Waterhouse Jun^r.⁴ has kindly given me the name of the Cape Beetle which I mentioned to you. It is Peritrichia cinerea, a small, long-legged Lamellicorn belonging to the characteristic S. African Pachycnemidæ. The ♂ is slaty-grey clothed with whitish hairs, and the ♀ rufous-brown with pale-yellowish hairs. Though the ♀ has been described as a distinct species (P. proboscidea), I found that the sexes were placed together as one species in the British Museum collection, but without the knowledge that they were sexes of the same insect.⁵

I have so often taken the two in copulâ that you may rely on the correctness of this observation.

I will not forget to send you any points of importance which appear to bear upon your present special subject of research, if I am fortunate enough to chance upon them.

With my respects to M^rs. Darwin, I remain | Very faithfully yours, | Roland Trimen.

C. Darwin Esqre.