To B. D. Walsh 31 October 1868
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.1
I do not at all know what to think of your extraordinary cases of the cicadas.2 Prof. Asa Gray & Dr Hooker were staying here & I told them of the facts.3 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.4 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.5 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 Hartman6 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
- Letter no.
- Darwin, C. R.
- Walsh, B. D.
- Sent from
- Source of text
- Field Museum of Natural History, Chicago (Walsh 16)
- Physical description
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.
Please cite as
Darwin Correspondence Project, “Letter no. 6437,” accessed on 27 May 2016, http://www.darwinproject.ac.uk/DCP-LETT-6437