nt of beetles is the great
diversity noticeable in the outward form of the larva in different
families. The larva of a ground-beetle or a carnivorous water-beetle
(fig. 2 c) is an active elongate grub with well-armoured cuticle. The
head--carrying feelers, mandibles and two pairs of maxillae--is
succeeded by the three thoracic segments, each bearing a pair of
strong five-segmented legs, whose feet, like those of the adult, carry
two claws. Ten segments can be distinguished in the tapering abdomen,
the ninth frequently bearing a pair of tail-feelers (cerci), and the
tenth, attached ventrally to the ninth, having the anal opening at its
extremity and performing the function of a posterior limb, supporting
and temporarily fixing the tail end of the insect on the surface over
which it crawls. Such a typically "campodeiform" grub, moving actively
about in pursuit of prey, is the one extreme of larval structure to be
noticed among the Coleoptera. The other is exemplified by the white,
wrinkled, soft-skinned, legless grub of a weevil, which lives
underground feeding on roots, or burrows in the tissues of plants
(fig. 3 b). Between these two extremes we find various transitional
forms: an active larva, as described above, but with four-segmented,
single-clawed legs, as among the rove-beetles and their allies; the
body well armoured, but slender and worm-like, with very short legs as
in wireworms and mealworms (figs. 18, 21 b); the body shortened, with
the abdomen swollen, but protected with tubercles and spines, and with
longish legs adapted for an active life, as in the predaceous larvae
of ladybirds; the body soft-skinned, swollen and caterpillar-like,
with legs well developed, but leading a sluggish underground life, as
in the grub of a chafer; the body soft-skinned and whitish, and the
legs greatly reduced in size, as in the wood-feeding grub of a
longhorn beetle. In the case of certain beetles whose larvae do not
find themselves amid appropriate food from the moment of hatching, but
have to migrate in search of it, an early larval stage, with legs, is
followed by later sluggish stages in which legs have disappeared,
furnishing examples of what is called hypermetamorphosis. For example,
the grub of a pea or bean beetle (_Bruchus_) is hatched, from the egg
laid by its mother on the carpel of a leguminous flower, with three
pairs of legs and spiny processes o