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Anatomy
The following discussion is intended to facilitate use of the keys and
descriptions, especially for those who are not familiar with this group of
insects. A glossary, which explains the terms used in this work, will be found
at the end of the book. The basic structure of all orthopteroids is generally
similar, although each order has its own peculiar characteristics involving
important structural and other features that have evolved as a result of their
specialized behavior. Fig. 6 illustrates the basic structure of an ulonate insect
of a familiar form, that of a short-horned grasshopper.
The body is made up of three regions: the head (h), the thorax (t), and
the abdomen (ab). On the head are a pair of antennae (a), three simple eyes,
or ocelli (0), although these may be reduced or absent, a pair of compound
eyes (e), and the mouthparts, i.e., structures associated with feeding. The
antennae vary considerably in length. The top of the head is the vertex (v);
the sides, or cheeks, are the genae (g); the front of the head, or face, is the
frons (1), often with a vertical ridge, or frontal costa (jc), whereas the posterior
part of the head is the occiput (oc). The ocelli are arranged, basically, in
a triangle, one ocellus near each antenna and the third in the middle of the
frons. The two compound eyes are generally large and usually prominent,
each being composed of a large number of facets, each of which is the cornea
of an individual component, or ommatidium, of the eye.
The mouthparts in all Ulonata are of a typical biting or chewing type,
consisting of two pairs of movable jaws, the mandibles (md), which are large
and usually heavy, and the maxillae (mx), which are located behind the
mandibles, together with the labium (li), which lies behind the maxillae.
Attached to the lower part of the frons, and above the mouthparts proper,
is the clypeus (c), to which is attached the labrum (lr), which functions as
an upper, or outer, lip. The labium acts as a lower lip and prevents loss of
food while the insect is chewing; it bears a pair of three-segmented
appendages, the labial palps. Similar palps, each with five segments, are
attached to the maxillae. The palps have a sensory function.
The thorax, i.e., the body region which has locomotion as its main
function, is made up of three segments: the prothorax (pr), the mesothorax
(ms), and the metathorax (mt). Each of these segments bears ventrally a pair
of legs. The uppermost part of the prothorax, which is generally bent down
over the sides of the rest of prothorax, is the pronotum, normally a large
and prominent structure. The mesonota and metanota, i.e., the uppermost
parts of the mesothorax and metathorax, respectively, each bear a pair of
wings (except in wingless species) and laterally a pair of spiracles (respiratory
pores). The fore wings, or tegmina (teg), are typically thickened, usually
close-veined and tough, serving to protect the more delicate membranous
hind wings, which are folded, fanlike, beneath the tegmina when not in use.
In some groups the pronotum is projected backward over the bases of the
wings. In the Orthoptera, sensu stricto, the pronotum is usually divided transversely
by a major furrow, or "typical" sulcus, into an anterior area, the
prozona (prz), and a posterior area, the metazona (mez). (Sometimes a less
prominent sulcus between the anterior margin of the pronotum and the
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