Hermanni (one of Dytiscidae or water-beetles) a strong ridge runs
parallel and near to the sutural margin of the elytra, and is crossed
by ribs, coarse in the middle part, but becoming gradually finer at
both ends, especially at the upper end; when this insect is held under
water or in the air, a stridulating noise is produced by the extreme
horny margin of the abdomen being scraped against the rasps. In a great
number of long-horned beetles (Longicornia) the organs are situated
quite otherwise, the rasp being on the meso-thorax, which is rubbed
against the pro-thorax; Landois counted 238 very fine ribs on the rasp
of Cerambyx heros.
[Fig.26. Hind-leg of Geotrupes stercorarius (from Landois). r. Rasp. c.
Coxa. f. Femur. t. Tibia. tr. Tarsi.]
Many Lamellicorns have the power of stridulating, and the organs differ
greatly in position. Some species stridulate very loudly, so that when
Mr. F. Smith caught a Trox sabulosus, a gamekeeper, who stood by,
thought he had caught a mouse; but I failed to discover the proper
organs in this beetle. In Geotrupes and Typhoeus, a narrow ridge runs
obliquely across (r, Fig. 26) the coxa of each hind-leg (having in G.
stercorarius 84 ribs), which is scraped by a specially projecting part
of one of the abdominal segments. In the nearly allied Copris lunaris,
an excessively narrow fine rasp runs along the sutural margin of the
elytra, with another short rasp near the basal outer margin; but in
some other Coprini the rasp is seated, according to Leconte (78. I am
indebted to Mr. Walsh, of Illinois, for having sent me extracts from
Leconte s Introduction to Entomology, pp. 101, 143.), on the dorsal
surface of the abdomen. In Oryctes it is seated on the pro-pygidium;
and, according to the same entomologist, in some other Dynastini, on
the under surface of the elytra. Lastly, Westring states that in
Omaloplia brunnea the rasp is placed on the pro-sternum, and the
scraper on the meta-sternum, the parts thus occupying the under surface
of the body, instead of the upper surface as in the Longicorns.
We thus see that in the different coleopterous families the
stridulating organs are wonderfully diversified in position, but not
much in structure. Within the same family some species are provided
with these organs, and others are destitute of them. This diversity is
intelligible, if we suppose that originally various beetles made a
shuffling or hissing noise by the rubbing together of any hard and
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