The Descent of Man

provided or degenerate males. Although the
mandibles of the common stag-beetle, and probably
of many other species, are used as efficient
weapons for fighting, it is doubtful whether
their great size can thus be accounted 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.