82 THE LIFE-STORY OF INSECTS [CH. 



'chrysalis' on account of the golden hue displayed 

 by the cuticle, and the term * chrysalis ' is sometimes 

 bestowed indiscriminately on any kind of pupa. It 

 has been shown by Poulton (1892) and others, that 

 the colour of a butterfly pupa is to some extent 

 affected by the surroundings of the caterpillar just 

 l>efore its last moult. 



Reference has been made (p. 58) to the power of 

 spinning silk possessed by many larvae; often the 

 principal use of this silk is to form some protection 

 for the pupa, the larva before its last moult con- 

 structing a cocoon within which the pupa may rest 

 safely. Many larvae bury themselves in the earth, 

 and the pupa lies in an earthen chamber, the lining 

 particles of soil fastened together by fine silken 

 threads. Larvae that feed in wood, like the cater- 

 pillar of the Goat-moth (Cossus) make a cocoon of 

 splinters spun together, while hairy caterpillars, such 

 as those of the Tiger-moths, work some of their hairs 

 in with the silk to make a firm cocoon (fig. 17 b). 

 On the other hand, those caterpillars known as 'silk- 

 worms ' make a dense cocoon of pure silk, consisting 

 of two layers, the outer of coarse and the inner of 

 fine threads. Silken cocoons very similar in appear- 

 ance are spun by the larvae of small Ichneumon-flies. 

 Many pupae lie in a loose cocoon formed of a few 

 interlacing threads, as for example the conspicuous 

 black and yellow banded pupa of the Magpie-moth 



