ARTHROPODA 



95 



iarly exemplified in the silk of commerce. The 

 caterpillar, in some cases, is gregarious, and 

 builds a common nest (Fig. 30). 



The beetles, Coleoptera, are, like the butter- 

 flies, endlessly numerous. They are characterised 

 by the striking difference in their two pairs of 

 wings, of which the anterior pair is strong and 

 horny, and forms, when at rest, a sheath which 



FlG. 29. A Moth, Saturnia pyri (S. Europe), with its Caterpillar, 

 A; its Cocoon, B\ Cocoon cut open to show Chrysalis, C\ 

 Adult insect, D. 



covers the thinner posterior pair of wings. The 

 metamorphosis is complete in this group also. 

 Fig. 31 shows an example which is typical except 

 in one respect the adult form, namely, is one of 

 7 



