LIBRARY

THE ANATOMY OF INSECTS 15
longitudinally the epicranium or top and back of the head into two epicranial
plates or sclerites.
Occiput - part of the epicranium between the vertex and the neck.
Vertex - top of head between the compound eyes and behind the frons;
usually carries the paired ocelli of orthopteroid insects and the three ocelli of
other groups.
Frons - a single sclerite between and below the branches of the epicranial
suture; carries the single frontal ocellus of orthopteroid insects.
Clypeus - a large double fused sclerite below or in front of the frons. It may
be divided into an upper or postclypeus and a lower or anteclypeus.
Labrum or upper lip - a movable sc1erite articulated to the lower margin of
the clypeus and covering the mandibles and upper side of the mouth.
Genre or cheeks -lateral regions back of and below the eyes; each may be
divided longitudinally by an occipital suture into the occt"put or dorsal area and
the poslgena or lateral region.
Cervicum or neck - the flexible area composed of the cervical sclerites and
surrounding membrane, and encircling the posterior opening of the head or the
foramen magnum.
Positions of the head. - The position of the head may be due to modifications
of structure of the thorax or to methods of feeding. In relation to the rest of
the body the head may be said to be one of the three following types:
Prognathous. - The main axis of the head is horizontal and the mouth
parts are directed forwards. This type is found in most predaciolls larne
and adult insects and may also be called the lhysanuriform type.
Hypognathous. - The main axis of the head is vertical and the mouth
parts are directed downwards and sometimes backwards. This condition
occurs in adult insects in many orders and is especially common in many
biting and chewing phytophagous insects and their larvce. This may also
be called the orthopteroid type.
AjJislognathous. - The hypognathous type is modified to the extent. that
the mouth parts arise far back on the venter of the head and are directed
downwards and backwards. This is the sucking or hemipteroicl
type.
Antenna:: (sing. antenna). - The antennre, feelers, or horns are a pair of segmented
sensory organs located in front of or between and sometimes partly
surrounded by the eyes, or they may arise from the sides of the face near the
bases of the mandibles. They may be shorter than the head or several times as
long as the body and are very greatly reduced in certain larva! and absent in
the order PROTURA. They not only vary greatly in size but also in form and
structure, attaining especially great diversity among the COLEOPTERA. The
commonly recognized forms are:
1. Setijorm or setaceous - bristle-shaped; slender, tapering apically by reduction
in the diameter of the segments; usually relatively short or
very long. In COLEOPTERA, DIPTERA, LEPIDOPTERA.
2. Filiform - very slender and thread-lil,e; segments of nearly equal di.