INTRODUCTION. 
81 
parenchyma or pulp urhich 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 he 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 ndth a eoating of silk ; those parts 
being made strongest, which, from their prominence. 
F 
