CH. III.] INSECTS WHICH FORM COCOONS. 57 



which is thus given to the two ends of the cocoon. 

 Sometimes the head and tail are curled opposite to 



ABC 



each other, fig. A, while at others the body assumes 

 the form of the letter S, fig. B. Hence the body 

 of the insect becomes the model of its cocoon. 

 The motions of the insect, in forming the different 

 parts of the cocoon, are very gradual. The man- 

 ner in which the layer of silk which serves for the 

 groundwork of the cocoon is spun, does not mate- 

 rially differ from that of the caterpillars ; but when 

 the network is somewhat advanced, it is observed to 

 acquire an external covering of hair, which stands 

 erect to a considerable height, as in fig. C. These 

 hairs have been stripped from those parts of the 

 body of the enclosed caterpillar which are placed 

 against the sides of the cocoon, the caterpillar being 

 observed at such time to fret itself against the inner 

 surface of the network, whereby the hairs are protru- 

 ded through the meshes of the net ; the basal portion 

 of these hairs still however remains within the co- 

 coon, and as a prickly unevenn.ess would be pro- 

 duced in the inner surface of the cocoon, which 

 would irritate the soft chrysalis when newly dis- 

 closed if the hairs were to remain in that position, 

 the insect, in order to remedy this inconvenience, 

 forces the basal portions of the hairs closely against 

 the inner surface of the cocoon, and fastens them 

 in that position with silken threads ; by this means 

 the outer parts of the hairs are brought to lie flat 

 upon the outer surface of the cocoon, which is then 



