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.
“My dear Sir,—The living beetles and the cocoons were found in a small paper packet containing the seeds. Those from which the beetles had emerged were much broken, and the larvæ had evidently attacked some of the other seeds. I am sorry to say that some of the injured ones were thrown away. I am glad that you are going to draw up a paper from Fritz Müller’s letters.