ARACHNIDA. 



189 



of exceeding minuteness, through which the filaments 

 are drawn. The fluid silk, which constitutes the 



Fig. 148.— gardex spidek. 



material whereof the thread is composed, is secreted 

 by a set of glands, situated in the interior of the 

 body. Lnhke the single line of a caterpillar, the 

 thread of the spider, delicate as it is, is seen to be 

 composed of hunch-eds of filaments, sometimes woven 

 together by zigzag lines, and thus exhibiting a struc- 

 ture of exquisite and most elaborate composition. 



Various are the purposes to which the different 

 species of spiders convert the delicate threads thus 

 produced. Some construct silken tubes or cells in 

 which to conceal themselves, and from this retreat 

 they issue to hunt for prey, in the vicinity of their 

 abode. Others throw their filaments about at 

 random, apparently to entangle passing insects 



