CH. XVI.] THE CATERPILLAR. 275 



of the extremities of the cylinder ; but so arrang-ed 

 as to furnish the insect with ready means both oi' in- 

 gress and egress. While this singularly constructed 

 mansion protects the insect from its numerous ene- 

 mies, it furnishes it also with food. It nibbles and 

 consumes successively the layers which compose 

 its case ; so that when tlie cylinder is examined, 

 after the lapse of a certain space of time, it vv'ill be 

 found at last to consist only of the outcimost roll. 

 Having eaten itself out of house and hold, it then 

 sets about constructing another dwelling. 



The last of the habitations formed by the cater- 

 pillar differs somewhat from the first ; it is larger in 

 size, to accommodate the insect, now grown more 

 bulky. The leaf is not bent so much, and conse- 

 quently it does not offer the same resistance: the 

 insect appears aware of this fact, and contents itself 

 with making its cordage less strong. Instead of 

 bending the leaf by little cables placed at intervals, 

 it spins a continuous web, which extends the whole 

 length of the leaf. This web, like the cords already 



described, is composed of two decussating sets of 

 fibres : the first set acted on by the weight of the 

 insect's body draws the leaf downwards ; the second 

 set secures in its proper place the additional curve 

 which has been thus gained. 



Within this cylinder the caterpillar undergoes its 

 metamorphosis "into a chrysalis and imago. Tn its 

 former state the skin is at first so soft that it requires 

 protection ; and to ensure it, the inside of the cell 

 is lined with a slight layer of silk. W^hen about to 



