278 NATURAL HISTORY. [CH. XVL 



now to spin a new set of threads ; one end of these 

 is glued to the old web, and the other end near to or 

 beyond the centre of the leaf, as it may seem neces- 

 sary. 



These two webs incline towards each other at a 

 certain angle. The effect upon the leaf is the same 

 as if the curve had been produced by threads nearly 

 double the length of those which compose either 

 web. The leaf having thus acquired a greater bend, 

 iJie insect mounts at the angular junction of the two 

 webs, and begins to spin a third set of threads, 

 which, like the first, has one end attached to the in- 

 dentations of the leaf, while the other is fastened 

 near the central nervure. This is then crossed with 

 a fourth web formed in the manner already de- 

 scribed. These parts of cross webs may be seen 

 rising one above another, until the requisite curve 

 has been given to the leaf. It may be asked why 

 the insect does not at once spin one long thread 

 instead of two shorter ones crossing each other % 

 Simply because it cannot : the length of the thread 

 is determined by the length of the animal's reach. 

 While engaged in fabricating these successive layers 

 of webs, the insect may frequently be seen de- 

 scending to cut the inferior threads, which, from the 

 greater tension of the superior one, have become 

 slack, and consequently useless. This operation it 

 performs by means of its fore-legs, using them as 

 we do our hands. When the insect feeds upon the 

 parenchyma and one membrane of the leaf, it in 

 extremely cautious not to touch the other mem- 

 brane or the nervures. By this means not only are 

 the materials of its covering provided, but the pro- 

 cess of fabricating it is greatly facilitated ; and the 

 tent, though considerably diminished in weight, is 

 not less firm, since the natural cordage (the nervures) 

 is left entire. The more minutely we examine the 

 works of nature, the more clearly shall we trace 

 evidence of design. Whether we contemplate the 



