as
been vividly described by Miall (1895).
Examples might be multiplied, but enough have been given to enforce the
conclusion that the forms of insect-larvae are wondrously varied, and
that frequently, within the limits of the same order or even family,
modifications of type may be found which are suited to various modes of
life adopted by different insects. A survey of the multitudes of insect
larvae--grubs, caterpillars, maggots--living on land, on plants,
underground, in the water; feeding on leaves, in stems, on roots, on
carrion, on refuse; by hunting or by lurking after prey; as parasites or
as scavengers, brings home to us most strongly the conclusion that each
larva is fitted to some little niche in the vast temple of life, each is
specially adapted to its part in the great drama of being.
CHAPTER VII
PUPAE AND THEIR MODIFICATIONS
The pupal stage is characteristic of the life-story of those insects
whose larvae have wing-rudiments in the form of inpushed imaginal discs,
and in all these insects there is, as we have seen, considerable
divergence in form between larva and imago. In the pupa the wings and
other characteristically adult structures are, for the first time,
visible outwardly; it is the instar which marks the great crisis in
transformation. The pupa rests, as a rule, in a quiescent condition, and
during the early period of this stage the needful internal changes, the
breaking down of many larval tissues, and their replacement by imaginal
organs, go on. Both outwardly and inwardly therefore, the insect
undergoes, at the pupal stage, a reconstruction necessitated by the
differences in form and often in habit, between the larva and the winged
adult; and the greater these differences, the more profound must be the
changes that mark the pupal stage.
From the prominence of imaginal structures in the pupa, it is at once
seen that the pupa of any insect must resemble the adult more nearly
than it resembles the larva. But in different groups of insects we find
different degrees of likeness between pupa and imago. In a beetle pupa
(see fig. 16 _c_), the appendages--feelers, jaws, legs, wings--stand out
from the body as do those of the perfect insect. This type is called a
_free_ pupa. The pupal cuticle has to be shed for the emergence of the
imago, but the pupa is already a somewhat reduced model of the final
instar, with abbreviated wings and doubled-up legs. A free pupa is
characteristic of
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