iform (fig.
4 b). The transverse fold of the hind-wing is towards the tip, about
two-thirds of the wing-length from the base. At this fold the median
nervure stops and is joined by a cross nervure to the radial, which
can be distinguished throughout its length from the subcostal. There
are four malpighian tubules. In the ovarian tubes of Adephaga small
yolk-chambers alternate with the egg-chambers, while in all other
beetles there is only a single large yolk-chamber at the narrow end of
the tube. The larvae (fig. 2 c) are active, with well-chitinized
cuticle, often with elongate tail-feelers (cerci), and with
five-segmented legs, the foot-segment carrying two claws.

[Illustration: FIG. 4.--_Mormolyce phyllodes_. Java. a, Labium; b,
maxilla; c, labrum; d, mandible.]

The generalized arrangement of the wing-nervure and the nature of the
larva, which is less unlike the adult than in other beetles,
distinguish this tribe as primitive, although the perfect insects are,
in the more dominant families, distinctly specialized. Two very small
families of aquatic beetles seem to stand at the base of the series,
the _Amphizoidae_, whose larvae are broad and well armoured with short
cerci, and the _Pelobiidae_, which have elongate larvae, tapering to
the tail end, where are long paired cerci and a median process,
recalling the grub of a Mayfly.

[Illustration: FIG. 5.--_Pheropsophus Jurinei_. W. Africa.]

[Illustration: FIG. 6.--_Carabus rutilans_. Spain.]

The _Dyticidae_ (fig. 2) are Adephaga highly specialized for life in
the water, the hind-legs having the segments short, broad and fringed,
so as to be well adapted for swimming, and the feet without claws. The
metasternum is without the transverse linear impression that is found
in most families of Adephaga. The beetles are ovoid in shape, with
smooth contours, and the elytra fit over the edges of the abdomen so
as to enclose a supply of air, available for use when the insect
remains under water. The fore-legs of many male dyticids have the
three proximal foot-segments broad and saucer-shaped, and covered
with suckers, by means of which they secure a firm hold of their
mates. Larval dyticids (fig. 2 b) possess slender, curved, hollow
mandibles, which are perforated at the tip and at the base, being thus
adapted for sucking the juices of victims. Large dyticid larvae often
attack small fishes and tadp