to feed there!

Some of the walking-stick insects, belonging to the order of crickets
and grasshoppers (Orthoptera), have their body elongated and narrow,
like a thin dry branch, and they have a way of sticking out their limbs
at abrupt and diverse angles, which makes the resemblance to twigs very
close indeed. Some of these quaint insects rest through the day and have
the remarkable habit of putting themselves into a sort of kataleptic
state. Many creatures turn stiff when they get a shock, or pass suddenly
into new surroundings, like some of the sand-hoppers when we lay them on
the palm of our hand; but these twig-insects put themselves into this
strange state. The body is rocked from side to side for a short time,
and then it stiffens. An advantage may be that even if they were
surprised by a bird or a lizard, they will not be able to betray
themselves by even a tremor. Disguise is perfected by a remarkable
habit, a habit which leads us to think of a whole series of different
ways of lying low and saying nothing which are often of life-preserving
value. The top end of the series is seen when a fox plays 'possum.

The leaf-butterfly _Kallima_, conspicuously coloured on its upper
surface, is like a withered leaf when it settles down and shows the
under side of its wings. Here, again, there is precise form-resemblance,
for the nervures on the wings are like the mid-rib and side veins on a
leaf, and the touch of perfection is given in the presence of whitish
spots which look exactly like the discolorations produced by lichens on
leaves. An old entomologist, Mr. Jenner Weir, confessed that he
repeatedly pruned off a caterpillar on a bush in mistake for a
superfluous twig, for many brownish caterpillars fasten themselves by
their posterior claspers and by an invisible thread of silk from their
mouth, and project from the branch at a twig-like angle. An insect may
be the very image of a sharp prickle or a piece of soft moss; a spider
may look precisely like a tiny knob on a branch or a fragment of lichen;
one of the sea-horses (_Phyllopteryx_) has frond-like tassels on various
parts of its body, so that it looks extraordinarily like the seaweeds
among which it lives. In a few cases, e.g. among spiders, it has been
shown that animals with a special protective resemblance to something
else seek out a position where this resemblance tells, and there is
urgent need for observations bearing on this selection of environment.