Darwin Correspondence Project

Down. | Bromley. | Kent. S.E.

Oct 31. 1868

My dear Sir

I am very much obliged for the extracts about the ``drumming'' which will be of real use to me.

I do not at all know what to think of your extraordinary cases of the cicadas. Prof. Asa Gray & Dr Hooker were staying here & I told them of the facts. They thought that the 13-year & the 17-year forms ought not to be ranked as distinct species unless other differences besides the period of development could be discovered. They thought the mere rarity of variability in such a point was not sufficient, & I think I concur with them.

The fact of both the forms presenting the same case of dimorphism is very curious. I have long wished that some one would dissect the forms of the male stag-beetle with smaller mandibles to see if they were well developed, i.e. whether there was an abundance of spermatozoa, & the same observations ought, I think, to be made on the rarer form of your cicada. Could you not get some observer such as Dr Hartman to note whether the females flocked in equal numbers to the ``drumming'' of the rarer form as to the common form?

You have a very curious & perplexing subject of investigation & I wish you success in your work—

My dear Sir | yours very sincerely | Charles Darwin