Agriculture Reference
In-Depth Information
Fig.
1 General structure of an
insect.
ciated with the mouthparts. The basic biting
mouthparts of an insect may be modified consid-
erably for piercing, lapping or sucking
(Fig.
3).
Piercing mouthparts, as in aphids and other
Hemiptera, include a hollow, needle-like stylet
(or stylet bundle), formed from the mandibles
and the maxillae; the piercing stylet is partly
guided by the labium, which forms a long, sup-
portive rostrum (see
Fig.
3a); some insects with
such mouthparts inject toxic saliva into plants
and can cause extensive galling. Many insects
have a pair of large, multifaceted compound
eyes. Insects may also possess simple eyes
(ocelli) which, in adults, may occur as a set of
three on the top of the head to form an ocellar
triangle. Antennae are present in most adults
and in many immature insects; they are, how-
ever, often inconspicuous in the latter. The an-
tennae are often slender and feeler-like, but the
individual components or subdivisions (the so-
called 'segments' or antennomeres - the former
term widely used as a term of convenience) are
sometimes much elaborated; the number of
antennal segments ranges from one to over a
Fig.
2 Frontal view of the head of a generalized
insect.
lower (ventral) surface of which forms the
epipharynx; a tongue-like hypopharynx; the jaws
(mandibles); the paired maxillae and a 'lower lip'
(labium). The mouthparts may include up to two
pairs of sensory, feeler-like palps (labial palps
and maxillary palps)
(Fig.
2). Various pairs of
glands (labial glands, mandibular glands, maxil-
lary glands and thoracic glands) are also asso-
