but this scraper in some cases has been specially modified for the
purpose. It is rapidly moved across the rasp, or conversely the rasp
across the scraper.
[Fig.25. Necrophorus (from Landois). r. The two rasps. Left-hand
figure, part of the rasp highly magnified.]
These organs are situated in widely different positions. In the
carrion-beetles (Necrophorus) two parallel rasps (r, Fig. 25) stand on
the dorsal surface of the fifth abdominal segment, each rasp (74.
Landois, Zeitschrift fur wissenschaft Zoolog. B. xvii. 1867, s. 127.)
consisting of 126 to 140 fine ribs. These ribs are scraped against the
posterior margins of the elytra, a small portion of which projects
beyond the general outline. In many Crioceridae, and in Clythra
4-punctata (one of the Chrysomelidae), and in some Tenebrionidae, etc.
(75. I am greatly indebted to Mr. G.R. Crotch for having sent me many
prepared specimens of various beetles belonging to these three families
and to others, as well as for valuable information. He believes that
the power of stridulation in the Clythra has not been previously
observed. I am also much indebted to Mr. E.W. Janson, for information
and specimens. I may add that my son, Mr. F. Darwin, finds that
Dermestes murinus stridulates, but he searched in vain for the
apparatus. Scolytus has lately been described by Dr. Chapman as a
stridulator, in the Entomologist s Monthly Magazine, vol. vi. p.
130.), the rasp is seated on the dorsal apex of the abdomen, on the
pygidium or pro-pygidium, and is scraped in the same manner by the
elytra. In Heterocerus, which belongs to another family, the rasps are
placed on the sides of the first abdominal segment, and are scraped by
ridges on the femora. (76. Schiodte, translated, in Annals and
Magazine of Natural History, vol. xx. 1867, p. 37.) In certain
Curculionidae and Carabidae (77. Westring has described (Kroyer,
Naturhist. Tidskrift, B. ii. 1848-49, p. 334) the stridulating organs
in these two, as well as in other families. In the Carabidae I have
examined Elaphrus uliginosus and Blethisa multipunctata, sent to me by
Mr. Crotch. In Blethisa the transverse ridges on the furrowed border of
the abdominal segment do not, as far as I could judge, come into play
in scraping the rasps on the elytra.), the parts are completely
reversed in position, for the rasps are seated on the inferior surface
of the elytra, near their apices, or along their outer margins, and the
edges of the abdominal segments serve as the scrapers. In Pelobius
331