worms, centipedes,
snails, and such forms, but after one has collected and reared some of
the young and watched them pass through the different stages and emerge
with wings they are much more easily recognized.

_Their Principal Characteristics_

[Illustration: Face of grasshopper enlarged showing parts; ant.,
antenna; eye, compound eye; oc., ocellus or simple eye; cl., clypeus;
lbr., labrum or upper lip; mx. p., maxillary palpus; lb. p., labial
palpus; lab., labium or lower lip.]

Young insects as a rule are soft like caterpillars and maggots, while
the old ones usually have a hard body wall, similar to the beetles and
wasps. The wings are usually thin and transparent though in some cases
they are leathery or hard as in case of beetles or covered with scales
as in the butterflies. The three pairs of legs are jointed and used for
running, climbing, jumping, swimming, digging or grasping. The feelers
or antennae are usually threadlike, clubbed, or resemble a feather and
extend forward or sidewise from the head. The large eyes are compound,
being made up of many great small units which, when magnified, resemble
honey-comb. In some cases two or three small bead-like eyes may be
present besides the two large eyes. The mouth parts of insects may be
formed for chewing, as in the grasshopper, or for sucking up liquids, as
in the mosquito. The mouth of an insect is built on an entirely
different plan from our own. Chewing insects have an upper and lower lip
and between these there are two pairs of grinding jaws. These jaws are
hinged at the side of the face and when chewing they come together from
either side so as to meet in the middle of the mouth. They therefore
work sidewise rather than up and down. The mouth parts of the sucking
insects are drawn out to form a sucking tube or proboscis as in case of
the butterfly or mosquito.

[Illustration: Mouth parts of grasshopper shown in relative position;
lbr., labrum; md., mandibles; hyp., hypopharynx; max., maxillae; lab.,
labium.]

[Illustration: Leg of grasshopper showing segmentation. The basal
segment c, is the coxa, the next t, the trochanter, the large segment f,
the femur, the long slender one ti, the tibia, and the three jointed
tarsus ta, with claws at the tip.]

The internal organs of insects are similar to those of other animals.
The digestive tube consists of oesophagus, gizzard, or stomach, and
intestines. The nervous system is well developed as shown by the