From G. R. Crotch [after 5 October 1868]1
The insect in question is a member of the group Pedinites family Tenebrionidae as defined by Jacquelin Duval in his “Genres des coleoptères d’Europe”.2
In this group the ♂s often differ very much from the ♀s as in Pedinus or hardly at all as in Phylax— stridulation has not been noticed in any member of this group hitherto. I find it in Pandarus & Heliopathes (including olocrates). In Litoborus an intermediate genus where the tarsi are hardly dilated in the ♂—I do not find it. In Pedinus where the tarsi are dilated, I do not find it however—3 a number of closely allied genera I have not been able to examine.
The insects sent are4
Heliopathes gibbus Fabr. Anglia common on the coast
Hel. cribratostriatus5 Chev Reynosa in Spain
on the Mountains— They seem to squeak very little in nature— at least I have only once noticed it alive & I have taken some thousands—but when dead it is often apparent in the process of pinning6
Note identifying insects and remarking on stridulation.
Please cite as
Darwin Correspondence Project, “Letter no. 6529,” accessed on 3 December 2016, http://www.darwinproject.ac.uk/DCP-LETT-6529