132 A BOOK OF INSECTS 



a dozen places, and then gently crushed into a dishevelled 

 heap. Having once assumed a position, by a wonderful 

 instinct he never moves or varies one of his many angles 

 by half a degree. The way the insect keeps up the delu- 

 sion is indeed almost as wonderful as the mimicry itself, 

 and you may turn him about and over and over, but he 

 is mere dried grass, and nothing will induce him to 

 acknowledge the animal kingdom by the faintest suspicion 

 of spontaneous movement." Tropical Phasmids are often 

 of great size, some attaining a length of nine inches from 

 head to tail, irrespective of their legs. 



In the great family of " carpet moths" {Geometridce) 

 nearly all the caterpillars are stick-like in form and colour, 

 and most of them assume an appropriate attitude when 

 at rest. The majority feed at night ; but when daylight 

 comes they take a firm hold upon a twig with their two 

 pairs of prolegs, and stretch out at an acute angle. To 

 lessen the strain that this posture imposes upon the body, 

 many of the species spin a delicate silken thread from 

 their mouth to the stem on which they rest ; and that 

 considerable reliance is placed upon this support may be 

 judged from the fact that if the thread be severed the 

 creature falls back with a jerk. Among the commonest 

 stick caterpillars are those of the swallow-tail moth {Oui*- 

 apteryx' sambucaria). They feed upon a variety of shrubs, 

 trees and herbaceous plants, and are often very abundant 

 in gardens ; yet they are seldom seen because of their 

 perfect resemblance to small brown twigs. 



Some caterpillars rely solely upon their coloration 

 for protection. That of the brimstone butterfly rests 

 during the day in a nearly straight position on the upper 

 side of a buckthorn leaf. It is fully exposed to view, 

 yet it tones so perfectly with its background as to be 

 practically invisible as a separate entity. Caterpillars 



