THE EVOLUTION OF THE CATERPILLAR 627 



appear in the more highly developed section of the Lepidoptera 

 known as butterflies, but in the higher groups of moths, quite 

 different, although analogous lines of development have been 

 followed. The most general is the growth of hair over the 

 caterpillar's entire body, a feature which marks one enormous 

 group as occupying a position of its own. Many among the 

 less speciahsed families have a certain amount of hair. Indeed, 

 it is the exception for a caterpillar to be entirely naked, but 

 in most cases the hairs are short and thinly scattered and 

 scarcely count in the general struggle for protection against 

 enemies. In the Bombyces, however, the hair is more or less 

 closely packed and often of considerable length. The cater- 

 pillar of the Garden Tiger Moth, commonly known as " woolly 

 bear," on account of its long silky coat, is a striking example. 

 Hairiness seems to be an extremely sure protection, not by 

 disguising the creature, but by rendering it distasteful to the 

 majority of its avian enemies. The calm fashion in which a 

 woolly bear will march about the naked ground in broad 

 daylight seems to indicate such a strong sense of security as 

 to have eliminated completely the instinct to conceal itself. 

 In the Ermine and Brown Tail caterpillars, which display 

 themselves openly on the bushes, the same evidence of protec- 

 tion is afforded, though, in most cases, at least partial seclusion 

 is sought during the dayUght hours. 



The pecuUarities of the Hawk Moth caterpillars have been 

 dealt with in detail elsewhere. They are, however, of the 

 customary cjdindrical form, but in the Elephant Hawks, the 

 singularly swollen segments behind the head, which conceal 

 the head at will, and the remarkable eyespots which adorn the 

 sides and give the creature an air of alertness, even while it is 

 asleep, seem sure evidence of development on protective lines, 

 as do the oblique stripes which almost universally adorn the 

 sides of the bodies of members of the group. The horn on the 

 tail, so mysterious a feature of this group, may be a relic of 

 the singular appendage of the Puss, or may, in ancestral forms, 

 have aided concealment by its resemblance to a thorn or 

 prickle. 



VII 



As I have hinted, in the most exalted group of this order, 

 the butterflies, every type of caterpillar seems to be repro- 

 duced and any attempt to classify butterflies by the larval 

 forms would certainly throw the usual system into chaos. 

 No two perfect insects more closely resemble each other 

 than do the Large White, Pieris brassicce, and the Small White, 

 P. rapce. Indeed, all but practised entomologists look upon 



