n of feeding does not produce any movement
externally. It was found in the limestone hills at Busan, the situation
of all others where mosses are most plentiful and delicate, and where
they partially clothe most of the protruding masses of rock."

_How these Imitations have been Produced._

To many persons it will seem impossible that such beautiful and detailed
resemblances as those now described--and these are only samples of
thousands that occur in all parts of the world--can have been brought
about by the preservation of accidental useful variations. But this will
not seem so surprising if we keep in mind the facts set forth in our
earlier chapters--the rapid multiplication, the severe struggle for
existence, and the constant variability of these and all other
organisms. And, further, we must remember that these delicate
adjustments are the result of a process which has been going on for
millions of years, and that we now see the small percentage of successes
among the myriads of failures. From the very first appearance of insects
and their various kinds of enemies the need of protection arose, and was
usually most easily met by modifications of colour. Hence, we may be
sure that the earliest leaf-eating insects acquired a green colour as
one of the necessities of their existence; and, as the species became
modified and specialised, those feeding on particular species of plants
would rapidly acquire the peculiar tints and markings best adapted to
conceal them upon those plants. Then, every little variation that, once
in a hundred years perhaps, led to the preservation of some larva which
was thereby rather better concealed than its fellows, would form the
starting-point of a further development, leading ultimately to that
perfection of imitation in details which now astonishes us. The
researches of Dr. Weismann illustrate this progressive adaptation. The
very young larvae of several species are green or yellowish without any
markings; they then, in subsequent moults, obtain certain markings, some
of which are often lost again before the larva is fully grown. The early
stages of those species which, like elephant hawk-moths (Chaerocampa),
have the anterior segments elongated and retractile, with large eye-like
spots to imitate the head of a vertebrate, are at first like those of
non-retractile species, the anterior segments being as large as the
rest. After the first moult they become smaller, comparatively; but it