The Descent of Man

dominal segment; whilst in the same number of
females there was not even a rudiment of the
rasp, the membrane of this segment being
transparent, and much thinner than in the male.
In H. cribratostriatus the male has a similar
rasp, excepting that it is not partially divided
into two portions, and the female is completely
destitute of this organ; the male in addition has
on the apical margins of the elytra, on each side
of the suture, three or four short longitudinal
ridges, which are crossed by extremely fine
ribs, parallel to and resembling those on the
abdominal rasp; whether these ridges serve as
an independent rasp, or as a scraper for the
abdominal rasp, I could not decide: the female
exhibits no trace of this latter structure.
Again, in three species of the Lamellicorn genus
Oryctes, we have a nearly parallel case. In
the females of O. gryphus and nasicornis the
ribs on the rasp of the pro-pygidium are less
continuous and less distinct than in the males;