146 THE INSECT WORLD. 



regain its equilibrium, and at the same time its former activity and 

 voracity. 



The Chrysalis, or Pupa. 



Having attained its full development, the caterpillar ceases to eat, 

 as at the approach of a moult, it empties its intestinal canal by 

 copious ejections ; it loses its colours, and becomes dull and livid, 

 and thus prepares itself to enter a new phase of its existence. 



Some, when about to transform themselves into chrysalides, 

 suspend themselves to foreign bodies. Others spin a cocoon, 

 composed of silk and other substances, which secures them against 

 the attacks of their enemies and the action of the atmosphere. 

 Those which suspend themselves can be divided under two heads, 

 according to the mode of their suspension : — i. Those which suspend 

 themselves perpendicularly by the tail. 2. Those which, after having 

 fixed themselves by the same part, suspend themselves horizontally, 

 by means of a silk thread passed round the body. 



To understand the difficulty which the first of these operations 

 presents, we must consider the problem which the caterpillar has to 

 solve. In this problem there are two unknown quantities to be dis- 

 covered. Firstly, the caterpillar must suspend itself firmly ; and 

 secondly, the pupa, having no communication with the object which 

 supports it, must be suspended in the same manner. This problem is. 

 difficult, apparently impossible, to solve. It is only by watching these 

 insects at work that one can discover the wonderful mysteries of 

 their lives. Swammerdam, Vallisnieri, and other observers who have 

 studied insects, had not, however, observed the manoeuvres of 

 caterpillars in this curious phase of their existence. It is to 

 Reaumur again that science is indebted for the most charming and 

 valuable observations on this point. He got together a great 

 number of caterpillars of the small Tortoise-shell Butterfly ( Vanessa 

 urticce)^ black prickly caterpillars which are common on the stinging- 

 nettle, where they live in companies, and suspend themselves by the 

 tail. When the time approaches at which the caterpillars of this 

 species ought to undergo their transformations, they usually leave the 

 plant which had up to that time served them as food. After having 

 wandered about a little, they select some convenient spot, where they 

 hang themselves up head downwards (Figs. 102, 103). 



In order to hang itself in this way, the caterpillar begins by cover- 

 ing, with threads drawn in different directions, a pretty large extent 

 of the surface of the body against which it wishes to fix itself. After 

 having covered it thus with a kind of thin cobweb, it adds different 



