My dear Darwin

Every spare minute I could find since I saw you has been spent in examining your Galapagos insects with a view to furnishing you with an account of them & of sending descriptions to Taylor’s Mg..¹ I am not quite prepared yet but have nearly done— The Carabideous insects which I thought belonged to our European genus Calathus do not—they form a new genus nearly allied to Calathus but have the claws of the tarsi simple instead of being pectinated— The Heteromera form three or four distinct genera—one genus possibly is identical with a genus described by Eschscholtz from California, and is certainly very near to it but Eschscholtz’s description is not quite detailed enough—² Hope³ may have the genus in question & if so I shall in a minute decide— Another genus contains three Galapagos species and they belong to a genus containing only 3 species to my knowledge & which is found in Chile & Peru—⁴ A third genus I have not yet worked out, but there is something very like it in California & also in Chile— About these Galapagos insects I will let you know more in a few days, finding I was mistaken about the Calathus I will look very closely to them—

The Butterfly which makes a clicking noise Doubleday (who it was made the remarks at the Ent. Soc.) informs me “is remarkable for having a sort of drum, at the base of the fore wing, between the costal nervure & the subcostal— these two nervures more over have a peculiar screw-like diaphragm or vessel in the interior—”⁵ I send you a wing in which you will see the little drum at the base & how large the 2^d. nervure from the anterior margin is— you will clearly see, also, the spiral vessel within— mind you, I thought this latter (spiral vessel always existed in the nervures of the wings which seem to be but an extension of the the lungs or rather air vessels, in the same way as the air vessels are extended into the bones of birds, but Doubleday knows more about these matters than myself having been working hard at the Butterfly nervures lately & having published (or sent to be published) a long paper on the subject in the Linn. Soc.⁶

So far I had got yesterday when I was interrupted and detained for two hours and a half—kept ’till six o’clock—

I have found the St. Paul’s Island Insects— they are all right, even the Feronia but the feronia is a parasitic fly— The name Feronia was given by D^r. Leach⁷ to a genus of flies closely allied to Hippobosca (the species of which are parasitic upon Cattle &c—) on the one hand and to Stenopteryx on the other— This last is the generic name for those narrow and sharply pointed winged flies which are found in the Swallow’s nest— It would be well in your new Edition to alter the name Feronia to Olfersia a name given by Wiedemann⁸ to the same genus because Leache’s name had been previously occupied.— The only notice of the habits I can find of Olfersia is in these words—(speaking of one of the species.) “M. Al. Lefebre l’a trouvée en Sicile sur le Heron”—⁹ Your’s appears to be a new species— there are but two or three known.

Lund’s list of recent & fossil species I have copied out—¹⁰ I should be very careful, judging from all I can learn of his specific determinations (& even generic) in putting too much faith in the list in question— I believe there are far too many species made—

I enclose a list of the fossil genera which I have discovered amongst M. Claussen’s specimens¹¹ & give what appears to me to be the probable number of species of each, contained in our collection— I will write again soon, and in the mean time look over my notes about Lund’s species &c

Believe me | Faithfully yours | Geo. R. Waterhouse

The other questions you left with me I will endeavour to answer in my next— I hope you are better— pray do not bother yourself for form sake &c &c to answer or acknowledge this