o_ (Sexton Beetle).
Europe.]

The _Silphidae_, or carrion beetles, form one of the best-known
families of this group. They are rotund or elongate insects with
conical front haunches, the elytra generally covering (fig. 10) the
whole dorsal region of the abdomen, but sometimes leaving as many as
four terga exposed (fig. 11). Some of these beetles are brightly
coloured, while others are dull black. They are usually found in
carrion, and the species of _Necrophorus_ (fig. 11) and _Necrophaga_
are valuable scavengers from their habit of burying small vertebrate
carcases which may serve as food for their larvae. At this work a
number of individuals are associated together. The larvae that live
underground have spiny dorsal plates, while those of the _Silpha_
(fig. 10) and other genera that go openly about in search of food
resemble wood-lice. About 1000 species of _Silphidae_ are known.
Allied to the _Silphidae_ are a number of small and obscure families,
for which reference must be made to monographs of the order. Of
special interest among these are the _Histeridae_, compact beetles
(fig. 12) with very hard cuticle and somewhat abbreviated elytra, with
over 2000 species, most of which live on decaying matter, and the
curious little _Pselaphidae_, with three-segmented tarsi, elongate
palpi, and shortened abdomen; the latter are usually found in ants'
nests, where they are tended by the ants, which take a sweet fluid
secreted among little tufts of hair on the beetles' bodies; these
beetles, which are carried about by the ants, sometimes devour their
larvae. The _Trichopterygidae_, with their delicate narrow fringed
wings, are the smallest of all beetles, while the _Platypsyllidae_
consist of only a single species of curious form found on the beaver.

[Illustration: FIG. 12. _Hister iv-maculatus_ (Mimic Beetle). Europe.]

[Illustration: FIG. 13. _Oxyporus rufus_. Europe.]

[Illustration: FIG. 14. _Stenus biguttatus_. Europe.]

The _Staphylinidae_, or rove-beetles--a large family of nearly 10,000
species--may be known by their very short elytra, which cover only two
of the abdominal segments, leaving the elongate hind-body with seven
or eight exposed, firm terga (figs. 13, 14). These segments are very
mobile, and as the rove-beetles run along they often curl the abdomen
upwards and forwards like the tail of a scorpion. The _Staphylinid_
larvae are ty