INTRODUCTION. 81 



parenchyma or pulp which constitutes its only 

 food. In this way it excavates a portion of the 

 leaf, leaving nothing but the thin superficial mem- 

 branes, which it takes particular care not to injure, 

 as they form the material from which the mantle is 

 to be manufactured. The latter is composed of two 

 equal and similar pieces, each forming one-half, 

 shaped and united with as much regularity and 

 precision as if executed by the most skilful artist. 

 The difficulty of the task is increased by the pieces 

 not being of regular figure, each of them being 

 one-half wider at the one end than the other, 

 and each side presenting a different curvature, the 

 one slightly concave and the other convex. When 

 the two pieces are cut into the requisite shape, they 

 still continue to adhere to the leaf by means of the 

 small crenatures left by the operator's teeth, and it 

 now remains only to sew the two portions together. 

 For this purpose it employs the silken thread, which 

 every caterpillar can spin, and attaches the two edges 

 so firmly and neatly, that it is difficult, when the 

 habit is completed, to discern the point of junction 

 even by the aid of a lens. A rounded form is 

 given to it by its being at first moulded, as it were>> 

 on the body of the insect itself, and its dimensions 

 are easily increased by the walls being pushed 

 outwards. The interior is freed from inequalities 

 by the pressure of the insect's head, and then lined 

 and strengthened with a coating of silk ; those parts 

 being made strongest, which, from their prominence* 



