258 NATURAL HISTORY. [CH. XV. 



part to which the mouth of its mantle is attached ; 

 and as it consumes the intervening substance* it 

 renders the epidermis so transparent, that its own 

 body and motions became perfectly visible. As the 

 pulpy substance nearest to the mouth of the case 

 becomes exhausted, the insect is of course forced to 

 advance farther in search of a fresh supply; the 

 body is, therefore, gradually dragged out of the 

 case, until at last little remains in it except the tail : 

 hence the necessity of fastening the mantle to the 

 leaf, as without this precaution it would drop off, 

 leaving the insect defenceless. If the leaf be in the 

 slightest degree agitated, it immediately retreats 

 backward into its case, so that whether feeding or 

 reposing it is always under cover. 



The following figures show not only that the case 

 of the insect is fixed at an angle more or less in- 

 clined to the under surface of the leaf, but likewise 

 give a correct representation of the mantle itself; 

 the shape, however, frequently varies : in some in- 

 stances, instead of being indented, it is simply a 

 cylinder slightly curved. 



Fig. 1, a mantle with a serrated border. 



2, a mantle which is cylindrical, and fixed at an angle on the leaf. 



Other caterpillars, more sagacious than that 

 already described, mine the leaf near one of its 



