Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

RESEMBLANCES AMONG ANIMALS. 123
external form and colouring of animals is adapted to
be useful to them, either by concealing them from their
enemies or from the creatures they prey upon. It has,
I hope, been shown that the subject is one of much
interest, both as regard a true comprehension of the
place each animal fills in the economy of nature, and
the means by which it is enabled to maintain that
place; and also as teaching us how important a part
is played by the minutest details in the structure
of animals, and how complicated and delicate is the
equilibrium of the organic world.
My exposition of the subject having been necessarily
somewhat lengthy and full of details, it will be as
well to recapitulate its main points.
There is a general harmony in nature between the
colours of an animal and those of its habitation.
Arctic animals are white, desert animals are sandcoloured; dwellers among leaves and grass are green
nocturnal animals are dusky. These colours are not
universal, but are very general, and are seldom reversed. Going on a little further, we find birds,
reptiles, and insects, so tinted and mottled as exactly
to match the rock, or bark, or leaf, or flower, they
are accustomed to rest upon, — and thereby effece
tually concealed. Another step in advance, and we
have insects which are formed as well as coloured so
as exactly to resemble particular leaves, or sticks, or
mossy twigs, or flowers; and in these cases very
peculiar habits and instincts come into play to aid
in the deception and render the concealment more