From Arthur Gardiner Butler   19 July 1870

Dear Sir

I am sorry that your note should have reached me whilst I am taking holidays, because, as I am very ignorant of Heterocerous Lepidoptera, I cannot, whilst away from the Museum, help you to the name of Trimen’s Moth, I am pretty sure that Iris is the name I suppose you are sure about the Gynanisa being all right?¹

The two species mentioned by D^r Wallace are Bombyx Pernyi & B. Yama-mai;² there is an interesting note on the two species in the Proceedings of the Ent. Soc. for this year, in which D^r Wallace states that hybrid eggs between these species proved fertile; hybrids in the imago state were exhibited at the Soc. 3 or 4 Meetings back.³

I have recently been trying some experiments with Vanessa Urticæ (the small Tortoiseshell Butt.),⁴ breeding in the dark & in differently coloured bottles, the only effects produced were dwarfed examples of a deeper tint than usual & the smaller the dwarf, the deeper the tint, as though the same amount of colour had been spread over a smaller area & thus had become intensified: The caterpillars showed a marked disinclination to change to pupa in the dark for I tried experiments by shutting out the light first on one side of my breeding cage & then on the other & the caterpillars invariably suspended themselves on the lighter side; when both ends were darkened they suspended themselves in the middle.

Believe me to be | yours very sincerely | A G Butler.

Ch. Darwin Esq | &c &c &c