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. So close 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- 



