us other families of the Clavicornia may be mentioned the
_Cucujidae_ and _Cryptophagidae_, small beetles, examples of which may
be found feeding on stored seeds or vegetable refuse, and the
_Mycetophagidae_, which devour fungi. The _Nitidulidae_ are a large
family with 1600 species, among which members of the genus
_Meligethes_ are often found in numbers feeding on blossoms, while
others live under the bark of trees and prey on the grubs of boring
beetles.

HETEROMERA.--This tribe is distinguished by the presence of the normal
five segments in the feet of the fore and intermediate legs, while
only four segments are visible in the hind-foot. Considerable
diversity is to be noticed in details of structure within this group,
and for an enumeration of all the various families which have been
proposed and their distinguishing characters the reader is referred to
one of the monographs mentioned below. Some of the best-known members
of the group belong to the _Tenebrionidae_, a large family containing
over 10,000 species and distributed all over the world. The
tenebrionid larva is elongate, with well-chitinized cuticle, short
legs and two stumpy tail processes, the common mealworm (fig. 21)
being a familiar example. Several species of this family are found
habitually in stores of flour or grain. The beetles have feelers with
eleven segments, whereof the terminal few are thickened so as to form
a club. The true "black-beetles" or "churchyard beetles" (_Blaps_)
(fig. 22) belong to this family; like members of several allied genera
they are sooty in colour, and somewhat resemble ground beetles
(_Carabi_) in general appearance.

[Illustration: FIG. 21.--(a) _Tenebrio molitor_ (Flour Beetle).
Europe. (b) Larva, or mealworm.]

[Illustration: FIG. 22.--_Blaps mortisaga_ (Churchyard Beetle).
Europe.]

[Illustration: FIG. 23.--_Meloe proscarabaeus_ (Oil Beetle). Europe.]

[Illustration: FIG. 24.--_Lytta vesicatoria_ (Blister Beetle).
Europe.]

The most interesting of the Heteromera, and perhaps of all the
Coleoptera, are some beetles which pass through two or more larval
forms in the course of the life-history (hypermetamorphosis). These
belong to the families _Rhipidophoridae_ and _Meloidae_. The latter
are the oil beetles (fig. 23) or blister beetles (fig. 24), insects
with rather soft cuticle, the elytra (often abbreviated) not fitting
closely to