compare them with the tegulae
of Hymenoptera, but the older view was securely established by the
demonstration in pupal elytra by J. G. Needham (1898) and W. L. Tower
(1903), of nervures similar to those of the hind-wing, and by the proof
that the small membranous structures present beneath the elytra of
certain beetles, believed by Meinert to represent the whole of the true
fore-wings, are in reality only the alulae.

_Structure._--Besides the conspicuous character of the elytra, beetles
are distinguished by the adaptation of the jaws for biting, the
mandibles (fig. 1, Bb) being powerful, and the first pair of maxillae
(fig. 1, Bc) usually typical in form. The maxillae of the second pair
(fig. 1, Bd) are very intimately fused together to form what is called
the "lower lip" or labium, a firm transverse plate representing the
fused basal portions of the maxillae, which may carry a small median
"ligula," representing apparently the fused inner maxillary lobes, a
pair of paraglossae (outer maxillary lobes), and a pair of palps. The
feelers of beetles differ greatly in the different families (cf. figs.
2b, 9b and 26b, c); the number of segments is usually eleven, but may
vary from two to more than twenty.

The head is extended from behind forwards, so that the crown
(epicranium) is large, while the face (clypeus) is small. The chin
(gula) is a very characteristic sclerite in beetles, absent only in a
few families, such as the weevils. There is usually a distinct labrum
(fig. 1, Ba).

The prothorax is large and "free," i.e. readily movable on the
mesothorax, an arrangement usual among insects with the power of rapid
running. The tergite of the prothorax (pronotum) is prominent in all
beetles, reaching back to the bases of the elytra and forming a
substantial shield for the front part of the body. The tergal regions of
the mesothorax and of the metathorax are hidden under the pronotum and
the elytra when the latter are closed, except that the mesothoracic
scutellum is often visible--a small triangular or semicircular plate
between the bases of the elytra (fig. 1, A). The ventral region of the
thoracic skeleton is complex, each segment usually possessing a median
sternum with paired episterna (in front) and epimera (behind). The
articular surfaces of the haunches (coxae) of the fore-legs are often
conical or globular, so that each limb works in a ball-and-socket joint,
while the hind haunches are large, displacing the vent