for. We have seen that they are used by the Lucanus elaphus of N.
America for seizing the female. As they are so conspicuous and so
elegantly branched, and as owing to their great length they are not
well adapted for pinching, the suspicion has crossed my mind that they
may in addition serve as an ornament, like the horns on the head and
thorax of the various species above described. The male Chiasognathus
grantii of S. Chile a splendid beetle belonging to the same family has
enormously developed mandibles (Fig. 24); he is bold and pugnacious;
when threatened he faces round, opens his great jaws, and at the same
time stridulates loudly. But the mandibles were not strong enough to
pinch my finger so as to cause actual pain.
Sexual selection, which implies the possession of considerable
perceptive powers and of strong passions, seems to have been more
effective with the Lamellicorns than with any other family of beetles.
With some species the males are provided with weapons for fighting;
some live in pairs and shew mutual affection; many have the power of
stridulating when excited; many are furnished with the most
extraordinary horns, apparently for the sake of ornament; and some,
which are diurnal in their habits, are gorgeously coloured. Lastly,
several of the largest beetles in the world belong to this family,
which was placed by Linnaeus and Fabricius as the head of the Order.
(72. Westwood, Modern Classification, vol. i. p. 184.)
STRIDULATING ORGANS.
Beetles belonging to many and widely distinct families possess these
organs. The sound thus produced can sometimes be heard at the distance
of several feet or even yards (73. Wollaston, On Certain Musical
Curculionidae, Annals and Mag. of Nat. Hist. vol. vi. 1860, p. 14.),
but it is not comparable with that made by the Orthoptera. The rasp
generally consists of a narrow, slightly-raised surface, crossed by
very fine, parallel ribs, sometimes so fine as to cause iridescent
colours, and having a very elegant appearance under the microscope. In
some cases, as with Typhoeus, minute, bristly or scale-like
prominences, with which the whole surrounding surface is covered in
approximately parallel lines, could be traced passing into the ribs of
the rasp. The transition takes place by their becoming confluent and
straight, and at the same time more prominent and smooth. A hard ridge
on an adjoining part of the body serves as the scraper for the rasp,
330