320 LEFIDOPTEROUS INSECTS. 



peated layers, become at last so thick and strong 

 that they resist all the attacks of the wind, and 

 all the injuries of the air, during eight or nine 

 months. 



About the beginning of October, or when the 

 frost commences, the whole community shut them- 

 selves up in the nest. During the winter they re- 

 main immoveable, and seemingly dead ; but, when 

 exposed to heat, they soon discover symptoms of 

 life, and begin to creep. In this country they 

 seldom go out of the nest till the middle or end of 

 April. When they shut themselves up for the 

 winter they are very small ; but, after they have fed 

 for some days in spring upon the young and tender 

 leaves, they find the nest itself, and all the entrances 

 to it, too small for the increased size of their bodies, 

 To remedy this inconvenience, these creatures know 

 how to enlarge both the nest and its passages, by 

 additional operations accommodated to their pre- 

 sent state. Into these new lodgings they retire when 

 they want to repose, to screen themselves from the 

 injuries of the weather, or to cast their skins. In 

 fine, after casting their skins several times, the time 

 of their dispersion arrives. From the beginning to 

 near the end of June they lead a solitary life. Their 

 social disposition is no longer felt. Each of them 

 spins a pod of coarse brownish silk. In a few days 

 they are changed into chrysaiids, and, in eighteen 

 or twenty days more, are transformed into butter- 

 flies. 



The modes adopted by caterpillars to screen 

 themselves from observation are as various as they 



