ll adapted for the capture of small
insect-victims. The larvae are more specialized than those of other
Adephaga, the head and prothorax being very large and broad, the
succeeding segments slender and incompletely chitinized. The fifth
abdominal segment has a pair of strong dorsal hook-like processes, by
means of which the larva supports itself in the burrow which it
excavates in the earth, the great head blocking the entrance with the
mandibles ready to seize on any unwary insect that may venture within
reach.

[Illustration: FIG. 9.

a _Gyrinus sulcatus_ (Grooved Whirligig). Europe.
b Antenna of _Gyrinus_.
c Larva of _Gyrinus_.]

Two or three families may be regarded as aberrant Adephaga. The
_Paussidae_ are a very remarkable family of small beetles, mostly
tropical, found only in ants' nests, or flying by night, and
apparently migrating from one nest to another. The number of antennal
segments varies from eleven to two. It is supposed that these beetles
secrete a sweet substance on which the ants feed, but they have been
seen to devour the ants' eggs and grubs. The _Gyrinidae_, or whirligig
beetles (fig. 9), are a curious aquatic family with the feelers (fig.
9, b) short and reduced as in most _Paussidae_. They are flattened
oval in form, circling with gliding motion over the surface film of
the water, and occasionally diving, when they carry down with them a
bubble of air. The fore-legs are elongate and adapted for clasping,
while the short and flattened intermediate and hind legs form very
perfect oar-like propellers. The larva of _Gyrinus_ (fig. 9, c) is
slender with elongate legs, and the abdominal segments carry paired
tracheal gills.

STAPHYLINOIDEA.--The members of this tribe may be easily recognized by
their wing-nervuration. Close to a transverse fold near the base of
the wing, the median nervure divides into branches which extend to the
wing-margin; there is a second transverse fold near the tip of the
wing, and cross nervures are altogether wanting. There are four
malpighian tubes, and all five tarsal segments are usually
recognizable. With very few exceptions, the larva in this group is
active and campodeiform, with cerci and elongate legs as in the
Adephaga, but the leg has only four segments and one claw.

[Illustration: FIG. 10.--_Silpha quadripunctata_. Europe.]

[Illustration: FIG. 11.--_Necrophorus vespill