Then followed three letters, January 3rd, March 24th, and March 27th, 1878; the first written when Darwin was sending another number of _Kosmos_, the second when sending his photograph, the third enclosing a letter from Fritz Müller containing some very interesting observations on mimicry in South American butterflies. He then wrote as follows:-- “_April 17/78._ “Down. “MY DEAR SIR,--I should be very much obliged if you could get some one to name the photographs of the enclosed insect and read the enclosed letter. It seems a pretty, but I think not new case of protective resemblance. One might fancy that the large ocelli on the under wings were a sexual ornament.--Perhaps these photographs might be worth exhibiting at the Entomolog. Soc.--I do not want them returned (unless indeed Dr. Zacharias wants them back, which is not probable) or the enclosed letter. “A single word with the name of the genus and if possible of the species, would suffice.-- “Pray forgive my troubling you and believe me “Yours faithfully, “CH. DARWIN. “I am glad that F. Müller’s letter interested you. He has published a paper with plates on the shape of the hairs or scales on the odoriferous glands of many butterflies, which I could send you, but I doubt whether you would care for it.” Darwin then sent another letter from Fritz Müller containing some interesting notes on odoriferous organs in butterflies, and on the occasional failure of the female insect to deposit her eggs on a plant which can serve as the food of the young larvæ. The beetles alluded to were a species of _Spermophagus_. The two letters printed below refer to the same subjects:-- “_May 15 [1878]._ “Down. “MY DEAR SIR,--I think the enclosed will interest you.--The letter to me need not be returned as I have had the only important passage for my work copied out.--In the letter F. M. [Fritz Müller] sent me seeds of _Cassia neglecta_ and several beetles arrived alive, having formed their cocoons, and gnawed their way out of the little peas or seeds.--These elegant beetles, with the knowledge of their manner of development may interest some Coleopterist. “I hope to hear some time about Dr. Zacharias’ photographs. I received your obliging letter from Paris. “Yours sincerely, “CH. DARWIN.” * * * * * “_May 25 [1878]._ “Down.