152 THE INSECT WOELD. 



shortens itself, and when it consequently distends the part of 

 its body which is outside the old skin, that part acts against the 

 edges of the slit, and gradually pushes the old skin upwards. 

 Thus the caterpillar skin ascends, its plaits are 

 pushed nearer and nearer together, and it is soon 

 reduced to a packet so small that it covers only 

 the end of the tail of the chrysalis (Fig. 106). 



But here comes the culminating point, the 

 most difficult part of the operation. The pupa, 

 which is shorter than the caterpillar, is at some 

 distance from the silky network to which it 

 must fix itself; it is only supported by that 

 extremity of the caterpillar's skin which had not 



Butterfly completing -, ,.. T . -, . , , 



the operation of cast- been split open. It nas neither legs nor arms, 

 and yet it must set itself free from this remaining 

 part of the skin, and reach the threads to which it is to suspend 

 itself. 



The supple and contractile segments of the chrysalis serve for 

 the limbs which are wanting to it. Between two of these seg- 

 ments, as with a pair of pincers, the insect seizes a portion of the 

 folded skin, and with such a firm hold that it is able to support 

 the whole of its body on it. It now curves its hinder parts 

 slightly, and draws its tail entirely out of the sheath in which it 

 was enclosed. It then reposes for an instant only, for it has not 

 yet finished the laborious operation of its deliverance. It must 

 free itself entirely from the dry skin which surrounds the ex- 

 tremity of its body. 



The insect curves the part which is below its tail in such a 

 manner that that part can embrace and seize the packet to which 

 it holds on. It then gives to its body a violent shock, which 

 makes it spin round many times on its tail, and that with great 

 rapidity. During all these pirouettes the chrysalis acts against 

 the skin ; the hooks of its legs fray the threads, and "break them 

 or disentangle themselves from them. Sometimes the threads do 

 not break at once. Then the animal recommences its revolutions 

 in an opposite direction, and this time it is almost certain to 

 succeed. Reaumur, however, saw a pupa which, after having 

 tired itself in vain in its endeavours to get entirely free of its 



