well-known Ground-beetles (Carabidae), the cuticle is less consistently
hard, firm sclerites segmentally arranged alternating with considerable
tracts of cuticle which remain feebly chitinised and flexible. Most of
the adephagous larvae (fig. 13) have a pair of stiff processes on the
ninth abdominal segment, and the insect, from its general likeness to a
bristle-tail of the genus Campodea, is often called a _campodeiform_
larva (Brauer, 1869). From such as these, a series of forms can be
traced among larvae of beetles, showing an increasing divergence from
the imago. The well-known wireworms--grubs of the Click-beetles
(Elateridae)--that eat the roots of farm crops, have well-armoured
bodies, but their shape is elongate, cylindrical, worm-like; and their
legs are relatively short, the build of the insect being adapted for
rapid motion through the soil. The grubs of the Chafers (Scarabaeidae)
are also root-eaters, but they are less active in their habits than the
wireworms, and the cuticle of their somewhat stout bodies is, for the
most part, pale and flexible; only the head and legs are hard and horny.
Usually an evident correspondence can be traced between the outward form
of any larva and its mode of life. For example, in the family of the
Leaf-beetles (Chrysomelidae) some larvae feed openly on the foliage of
trees or herbs, while others burrow into the plant tissues. The exposed
larvae of the Willow-beetles (Phyllodecta, fig. 14) have their somewhat
abbreviated body segments protected by numerous spine-bearing, firm
tubercles. But the grub of the 'Turnip Fly' (Phyllotreta) which feeds
between the upper and lower skins of a leaf, or of _Psylliodes
chrysocephala_ (fig. 15), which burrows in stalks, has a pale, soft
cuticle like that of a caterpillar.

[Illustration: Fig. 14. (_a_) Willow-beetle (_Phyllodecta vulgatissima_)
and its larva (_b_). Magnified 5 times. After Carpenter, _Econ. Proc. R.
Dublin Soc_. vol. I.]