190 THE LIFE OF AN INSECT. 



Many larvse, however, form nests of various 

 kinds, in which they comfortably spend the dreary 

 days and nights of this stern season. " With this 

 view," write the excellent observers, Kirby and 

 Spence, "the larva of Cossus ligniperda forms a 

 covering of pieces of wood, lined with fine silk ; 

 those of some other moths excavate, under a stone, 

 a cavity exactly the size of their bodies, to which 

 they give all round a coating of silk; and the larva? 

 of Pieris Cratcegi enclose themselves, in autumn, in 

 cases of the same material, and thus pass the cold 

 season, in small societies of from two to twelve, 

 under a common covering formed of leaves. Bon- 

 net mentions a trait of the cleanliness of these in- 

 sects, which is almost ludicrous. He observed in 

 one of these nests a sort of sack, containing nothing 

 but grains of excrement ; and a friend assured him 

 that he had seen one of these caterpillars partly 

 protrude itself out of the case, the hind feet first, 

 to eject a similar grain ; so that it would seem the 

 society have on their establishment a scavenger, 

 whose business it is to sweep the streets, and 

 convey the rejected matters to one grand reposi- 

 tory. This, however singular, is rendered not 

 improbable, from the fact that beavers dig, in 



