86 
INTRODUCTION. 
body. Its whole weight consequently tends to draw 
the leaf forwards, while every successive thread of 
the superior set that is fixed, immediately secures 
the additional curve gained by the continued pressure. 
The effect of this mode of proceeding soon becomes 
visible in the appearance of the threads ; the lower 
ones become loose and floating, and those last spun 
alone continue tight. One convolution of the leaf 
being in this manner secured, the laborious little 
worlcman proceeds. to form a second, by fixing his 
cords further hack on the bent part of the leaf, and 
managing them as before. "When the last roll is 
completed, the Avhole is secured by a series of silken 
bands, one or two of which are placed at each ex- 
tremity of the cylinder; or it is fiistened with 
irregular threads, which form a kmd of thin web 
along the whole extent of the leaf. The catei-pillar 
now takes up its abode in the interior, and finds 
ample means of subsistence in the internal layers of 
its dwelling, -without injuring the outermost roll ; or 
if the latter be likewise consumed, it is mider the 
necessity of constructing another tenement. 
Reaumur, and several authors who have followed 
him, assert, that when these leaf-rollers are unable 
to overcome the resistance of the leaf by the mecha- 
nism just described, they render it more flexible by 
purposely gnawing the nervures and the thickest por- 
tions ; but others are inclined to regard this state- 
ment as erroneous. As they are often occupied a 
considerable time in forming their habitations, it is 
scarcely to be supposed that they always abstain 
