ral sclerites of
the first two abdominal segments (fig. 1, C). The legs themselves (fig.
1, A) are of the usual insectan type, but in many families one, two, or
even three of the five foot-segments may be reduced or absent. In
beetles of aquatic habit the intermediate and hind legs are modified as
swimming-organs (fig. 2, a), while in many beetles that burrow into the
earth or climb about on trees the fore-legs are broadened and
strengthened for digging, or lengthened and modified for clinging to
branches. The hard fore-wings (elytra) are strengthened with marginal
ridges, usually inflected ventrally to form epipleura which fit
accurately along the edges of the abdomen. The upper surface of the
elytron is sharply folded inwards at intervals, so as to give rise to a
regular series of external longitudinal furrows (striae) and to form a
set of supports between the two chitinous layers forming the elytron.
The upper surface often shows a number of impressed dots (punctures).
Along the sutural border of the elytron, the chitinous lamella forms a
tubular space within which are numerous glands. The glands occur in
groups, and lead into common ducts which open in several series along
the suture. Sometimes the glands are found beneath the disk of the
elytron, opening by pores on the surface. The hind-wings, when
developed, are characteristic in form, possessing a sub-costal nervure
with which the reduced radial nervure usually becomes associated. There
are several curved median and cubital nervures and a single anal, but
few cross nervures or areolets. The wing, when not in use, is folded
both lengthwise and transversely, and doubled up beneath the elytron; to
permit the transverse folding, the longitudinal nervures are
interrupted.

[Illustration: FIG. 1.--Structure of Male Stag-Beetle (_Lucanus
cervus_). A, Dorsal view; B, mouth organs; C, under side.]

[Illustration: FIG. 2.--Water Beetles (_Dyticidae_). a, Beetle; b, head
of beetle with feelers and palps; c, larva; d, pupa.]

Ten segments can be recognized--according to the studies of K. W.
Verhoeff (1804-1896)--in a beetle's abdomen, but the tenth sternite is
usually absent. On account of the great extension of the metathorax and
the haunches of the large hind-legs, the first abdominal sternite is
wanting, and the second is usually so much reduced that the foremost
apparent ventral sclerite of the abdomen represents the third sternite.
From this point backwards the succ