8 Evolution and Adaptation 
this information there is danger that the case may prove too 
much, for, if it should turn out that this remarkable case is 
accidental the view in regard to the resemblance may be 
endangered. 
Amongst caterpillars there are many cases of remarkable 
resemblances in color between the animal and its surroundings. 
The green color of many of those forms that remain on the 
leaves of the food-plant during the day will give, even to the 
most casual observer, the impression that the color is for the 
purpose of concealment ; and that it does serve to conceal 
the animal there can be no doubt. But even from the point 
of view of those who maintain that this color has been 
acquired because of its protective value it must be admitted 
that the color is insufficient, because some of these same green 
caterpillars are marvellously armed with an array of spines 
which are also supposed to be a protection against enemies. 
Equally well protected are the brown and mottled geometrid 
caterpillars. These have, moreover, the striking and unusual 
habit of fixing themselves by the posterior pairs of false legs, 
and standing still and rigid in an oblique position on the 
twigs to which they are affixed. Soclose is their resemblance 
to a short twig, that even when their exact position is known 
it is very difficult to distinguish them. 
Grasshoppers that alight on the ground are, in many cases, 
so similar to the surface of the ground that unless their 
exact location is known they easily escape attention, while the 
green color of the katydid, a member of the same group of 
orthoptera, protects it from view in the green foliage of the 
trees where it lives. The veinlike wings certainly suggest a 
resemblance to a leaf, but whether there is any necessity 
for so close an imitation may be questioned. 
There can be little doubt in some of these cases that the 
color of the animal may be a protection to it, but as has 
been hinted already, it is another question whether it 
acquired these colors because of their usefulness. Never- 
