84 INTEODUCTIOX. 



fibres and nervures over so comparatively large a 

 surface. This, however, they accomplish with 

 apparent ease, instructed by the same beneficent 

 Power that teacheth man knowledge, and who has 

 conferred 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 

 nervures, 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 observers 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, " ii'est que Tassemblage des fils files 

 successivement. Dans 1'instant que chaque fil vient 

 de sortir de la filiere, pendant qu'il est encore mol, 



