The
various differences referred to would, therefore, be brought about by
variation and survival of the fittest, just as surely as the length and
quality of cotton on the seed of the cotton-plant have been increased
by man's selection.
The larvae of insects have thus been wonderfully modified in order to
escape the numerous enemies to whose attacks they are exposed at this
period of their existence. Their colours and markings have become
marvellously adapted to conceal them among the foliage of the plant they
live upon, and this colour often changes completely after the last
moult, when the creature has to descend to the ground for its change to
the pupa state, during which period a brown instead of a green colour is
protective. Others have acquired curious attitudes and large ocelli,
which cause them to resemble the head of some reptile, or they have
curious horns or coloured ejectile processes which frighten away
enemies; while a great number have acquired secretions which render them
offensive to the taste of their enemies, and these are always adorned
with very conspicuous markings or brilliant colours, which serve as a
sign of inedibility and prevent their being needlessly attacked.
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