BUGS.
171
(macropterus) and imperfectly developed (brachypterus)
individuals of both sexes occur. The reasons for these curious
anomalies are not known.
The Heteroptera separate naturally into two well-marked
sections : (1) Gymnocerata, comprising those species with
conspicuous and often very long antennas. All these are terres-
trial, except the Gerridae which (save the more or less submarine
Aepophilus) live on the surface of water. (2) Cryptocerata, in
which the antennae are very short and stout and concealed in
cavities beneath the eyes. Most of the species are fully winged
and all are aquatic and usually fly at night from pond to pond,
They are very much subject to attack by the larval forms of
certain water-mites (Hydrachna), which attach themselves soon
after hatching to the softer parts of the integument of the bugs,
where they remain, extracting nourishment from their unfor-
tunate host, until the perfect mite escapes from the larval skin.
It is the Heteroptera which will engage our attention to-day,
and we shall first very briefly glance at their general structure.
The mouth parts take the form of a 3- or 4-jointed beak or
rostrum, consisting of the mandibles and maxillae modified into
4 sharp-pointed bristles (setae), grooved, more or less toothed
at the tip, and adjoining one another in such a way that channels
are formed up which the liquid food of these insects can be sucked,
aided by capillary attraction ; these setae are enclosed in a case
formed by the modified labium, and the whole organ when at
rest is carried beneath the head and thorax and between the
basal joints of the legs. In the carnivorous bugs the rostrum
is, as a rule, short and somewhat curved, but in the vegetarian
species it is much longer and straight. The head is provided
with 2 compound eyes (oculi) and usually 2 simple eyes (ocelli),
but the latter are absent in the Capsidae, Pyrrhocoridae and some
others. The antennae are 4-jointed, except in the Nabidae
(Damsel-bugs), Pentatomidae (Shield-bugs), and Hebridae, in which
they have 5 joints, and in the genus Coranus of Reduviidae, in
which they have 8. The antennae of Heteroptera, especially
in the Lygaeidae, are subject to a curious malformation known as
"oligomery," which consists in the absence of one of the joints
on one side and usually the lengthening of one of the adjacent
joints as if in compensation ; in these cases the joints are perfect
in form, as a rule. The cause of this phenomenon is not known.