inted feelers and the pair of large,
sub-globular, compound eyes are the most prominent features. Below the
head, however, may be seen, now coiled up like a watch-spring, now
stretched out to draw the nectar from some scented blossom, the
butterfly's sucking trunk or proboscis, situated between a pair of short
hairy limbs or palps (fig. 2). These palps belong to the appendages of
the hindmost segment of the head, appendages which in insects are
modified to form a hind-lip or _labium_, bounding the mouth cavity below
or behind. The proboscis is made up of the pair of jaw-appendages in
front of the labium, the _maxillae_, as they are called. Behind the
thorax is situated the _abdomen,_ made up of nine or ten recognisable
segments, none of which carry limbs comparable to the walking legs, or
to the jaws which are the modified limbs of the head-segments. The whole
cuticle or outer covering of the body, formed (as is usual in the group
of animals to which insects belong) of a horny (chitinous) secretion of
the skin, is firm and hard, and densely covered with hairy or scaly
outgrowths. Along the sides of the insect are a series of paired
openings or spiracles, leading to a set of air-tubes which ramify
throughout the body and carry oxygen directly to the tissues.

[Illustration: Fig. 2. A. Head of a typical Moth, showing proboscis
formed by flexible maxillae (_g_) between the labial palps (_p_); _c_,
face; _e_, eye; the structure _m_ has been regarded as the vestige of a
mandible. B. Basal part (_b_) of maxilla removed from head, with
vestigial palp (_p_). Magnified.]

Such a butterfly as we have briefly sketched lays an egg on the leaf of
some suitable food-plant, and there is hatched from it the well-known
crawling larva[1] (fig. 1 _b, c, d_) called a caterpillar, offering in
many superficial features a marked contrast to its parent. Except on the
head, whose surface is hard and firm, the caterpillar's cuticle is as a
rule thin and flexible, though it may carry a protective armature of
closely set hairs, or strong sharp spines. The feelers (fig. 3 _At_) are
very short and the eyes are small and simple. In connection with the
mouth, there are present in front of the maxillae a pair of _mandibles_
(fig. 3 _Mn_), strong jaws, adapted for biting solid food, which are
absent from the adult butterfly, though well developed in cockroaches,
dragon-flies, beetles, and many other insects. The three pairs of legs
on the segments of t