PBOTECTIVE COLOEATIOX. 135 



the upper wings, and prodnces, according to Dr. Seitz, a re- 

 semblance to a terrible-looking creature with red, fiery eyes 

 and vibrating ears ; the abdomen plays the part of a pointed 

 snout projecting between the eyes. This, it is supposed, is 

 sufficient to appal the most courageous and stout-hearted of 

 birds. 



In many of these cases the infinite resources believed to be 

 possessed by an insect for evading or terrifying or actually 

 injuring its enemies, are only paralleled by those of the 

 White Knight in "Alice, through the Looking Glass." 



Dimorphism in Coloration. 



If it is useful to an animal to resemble its surroundings, 

 either for aggressive or protective purposes, the advantages 

 must be greater when the colour can be changed in response 

 to changes in the environment, or difi'ers in accordance with 

 different environments. A green caterpillar is safe so long as 

 it remains uj)on a green leaf; but upon a twig or upon the 

 trunlc of the tree the conspicnons green colour betrays it. It 

 is quite common for caterpillars to exhibit a colour dimor- 

 phism ; some individuals of the same species being green, 

 others brown ; this is the most usual form of colour dimor- 

 phism, and it will be observed that both colours assimilate to 

 tints found in Nature. 



So far as is known, this difference of colour among individuals 

 of the same brood has no relation to any feature in the perfect 

 insect ; it is not, for instance, a marlc of sex. 



Mr. Poulton has justly pointed out the advantage which a 

 larva such as that of the Large Emerald moth {ireometra 

 papilionaria^ would have over other species, in being dimor- 

 phic : the larva itself is not unlike the catkins of the birch ; 

 there are green and brown larvae just as there are green and 



