Among the carpenter-grubs may be mentioned that of the purple
capricorn-beetle (_Callidium violaceum_), of which the Rev. Mr. Kirby
has given an interesting account in the fifth volume of the 'Linnæan
Transactions.' This insect feeds principally on fir timber which has
been felled some time without having had the bark stripped off; but
it is often found on other wood. Though occasionally taken in this
kingdom, it is supposed not to have been originally a native. The
circumstance of this destructive little animal attacking only such
timber as had not been stripped of its bark ought to be attended to
by all persons who have any concern in this article; for the bark is
a temptation not only to this, but to various other insects; and much
of the injury done in timber might be prevented, if the trees were all
barked as soon as they were felled. The female is furnished, at the
posterior extremity of her body, with a flat retractile tube, which
she inserts between the bark and the wood, to the depth of about a
quarter of an inch, and there deposits a single egg. By stripping off
the bark, it is easy to trace the whole progress of the grub, from
the spot where it is hatched, to that where it attains its full size.
It first proceeds in a serpentine direction, filling the space which
it leaves with its excrement, resembling sawdust, and so stopping all
ingress to enemies from without. When it has arrived at its utmost
dimensions, it does not confine itself to one direction, but works in
a kind of labyrinth, eating backwards and forwards, which gives the
wood under the bark a very irregular surface: by this means its paths
are rendered of considerable width. The bed of its paths exhibits,
when closely examined, a curious appearance, occasioned by the
gnawings of its jaws, which excavate an infinity of little ramified
canals. When the insect is about to assume its chrysalis state, it
bores down obliquely into the solid wood, to the depth sometimes of
three inches, and seldom if ever less than two, forming holes nearly
semi-cylindrical, and of exactly the form of the grub which inhabits
them. At first sight one would wonder how so small and seemingly so
weak an animal could have strength to excavate so deep a mine; but when
we examine its jaws, our wonder ceases. These are large, thick, and
solid sections of a cone divided longitudinally, which, in the act of
chewing, apply to each other the whole of their interior plane surface,
so that they grind the insect's food like a pair of millstones. Some
of the grubs are hatched in October; and it is supposed that about the
beginning of March they assume their chrysalis state. At the place
in the bark opposite to the hole from whence they descended into the
wood, the perfect insects gnaw their way out, which generally takes
place betwixt the middle of May and the middle of June. These insects
are supposed only to fly in the night, but during the day they may
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