210 THE HARMONIES OF NATURE. 



of the liquid element. During the inactive chrysalis state, it is 

 necessary that the open end of these cylindrical cases should be 

 sufficiently closed to prevent the intrusion of enemies, and still 

 admit the water necessary for their existence ; but a most admira- 

 ble instinct has taught the sagacious little creatures to provide 

 for this want by the interweaving of a grate, or portcullis, at 

 each end of their fortress, which at the same time keeps out 

 intruders, and admits the water. Several dendritic caterpillars 

 arm their cases in a no less curious manner with thorns taken 

 from the tree itself on which they dwell, thus causing the 

 nest to harmonize so perfectly with surrounding objects that it 

 is not very easily perceived. The thorns are all disposed with 



Small Ermine Moths. 



their points outwards, and are stuck into a strong glutinous 

 material of which the body of the case is composed, like the 

 spikes of a chevaux-de-frise. As long as the caterpillar remains 

 in its larval state, and is obliged to feed, it traverses the 

 branches freely, carrying with it the prickly home, and bearing 

 the whole of its weight as it moves. But when the pupal stage 

 has nearly arrived, the nest is suspended to the branch by 

 strong silken threads, and thenceforth remains immoveable. 



Among the social caterpillars those of the Small Ermine 

 Moth deserve particular notice. They live in large tents, placed 



