says Mr. Wallace again, "which rest during the day clinging to the
bark of dead or fallen trees; and the greater portion of these are
delicately mottled with grey and brown tints, which though
symmetrically disposed and infinitely varied, yet blend so
completely with the usual colours of the bark, that at two or three
feet distance they are quite undistinguishable."

In protective resemblances at their highest state of perfection the
colouring is not constant but, as Professor Poulton puts it in his
delightful book on "The Colours of Animals", "can be adjusted to
harmonise with changes in the environment or to correspond with the
differences between the environment of different individuals." The
seasonal change of colour in northern animals is a well-known
instance of the former, and the chameleon's alterations of hue of
the latter.

Besides General Resemblance, in which the general effects of
surrounding colours are reproduced, we have Special Resemblance, in
which the appearance of a particular object is copied in shape and
outline as well as in colour. Numerous instances will be found in
this book, and a "Leaf Insect" and a "Moss Insect" are illustrated.
But the classic example is the butterfly from the East Indies so
graphically described by Mr. Wallace, Kallima paralekta, which
always rests among dead or dry leaves and has itself leaf-like
wings spotted over with specks to imitate the tiny fungi growths on
the foliage it resembles. "It sits on a nearly upright twig, the
wings fitting closely back to back, concealing the antennae and
head, which are drawn up between their bases. The little tails of
the hind wings touch the branch and form a perfect stalk to the
leaf, which is supported in its place by the claws of the middle