84 
INTEODUCTION. 
fibres and nerrures over so comparatively large a 
sm^face. This, however, they accomplish with 
apparent ease, instructed by the same beneficent 
Power that teachcth man knowledge, and who has 
confeiTcd even on the lowest of his sentient creatures 
an instinct which operates with the most salutary 
regularity, and is perfectly adequate to the supply 
of all their wants. 
Before a caterpillar of this sort commences its 
operations, it seems to take a survey of the leaf, in 
order to discover the part best adapted to its purpose. 
By availing itself of some natural inflection or cur- 
vature, such as may generally be found even in the 
flattest leaves, its labour is sometimes considerably 
lessened. It then takes up its position nearly mid- 
way between the edge of the leaf and the place to 
which it desires to draw it, — the latter being gene- 
rally the mid-rib, or some one of the principal 
nemircs, — and spins a multitude of threads between 
these two points. These threads are the mechanical 
means by which the operation is to be accomplished. 
The curvature once formed, they easily prevent the 
recoil of the leaf, but it is not so obvious in what 
manner they cause it to roll up. One of the most 
philosophical obseiwers that ever laboured in this field 
of natural history, confesses that he was unable to 
satisfy himself how this effect was produced, although 
the operation was going on under his eyes. “ Le 
paquet," he says, “ n est que Tassemblage des fils files 
successivement. Dans I’instant que chaque fil vient 
de sortir de la fili&e, pendant qu’il est encore mol, 
