Thanks BDW for extracts about "drumming" [of male Cicada to attract females].
Asa Gray and Hooker doubt that 13–year and 17–year Cicada forms should be considered distinct species. CD is inclined to agree with them.
Suggests observations be made of ratio of females to males in the rarer form.
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 D
You have a very curious & perplexing subject of investigation & I wish you success in your work—
My dear Sir | yours very sincerely | Charles Darwin
- f1 6437.f1For one of the extracts sent by Walsh, see the memorandum from B. D. Walsh, [before 31 October 1868].
- f2 6437.f2See letter from B. D. Walsh, 29 August 1868. CD also commented on the cicadas in his letter to Walsh of 21 September 1868.
- f3 6437.f3A group of guests, including Asa Gray and Joseph Dalton Hooker, stayed at Down House from October 24 (see letter to John Tyndall, 20 October 1868 and n. 1).
- f4 6437.f4Walsh had described another difference between the two cicada forms in the shape of the genital hooklet (see letter from B. D. Walsh, 29 August 1868).
- f5 6437.f5No letter from Walsh containing such a reference to dimorphism has been found.
- f6 6437.f6CD refers to William Dell Hartman (see memorandum from B. D. Walsh, [before 31 October 1868]).