THE SPIDER. 



153 



air that it disengages under the leaf of some aquatic 

 plant, and weaves around the bubble a tissue that keeps 

 it from moving away ; the spider 

 then goes up and gets another FIG. 86. 



bubble in the same manner, 

 brings it down, and adds it to the 

 first. By repeating these oper- 

 ations enough air is collected to 

 last some time, and the little 

 creature now encloses the whole 

 in a closely-woven net, and 

 weaves for itself a chamber as 

 large as a walnut, having an 

 opening below for ingress and 

 egress. The water-spider is car- 

 nivorous, like all other spiders, 

 and feeds indifferently on ter- 

 restrial and aquatic insects ; 

 when it has seized a prey, the 

 latter is attached to a thread 

 and dragged into the den for 

 consumption at leisure. The 

 water-spider is found in most calm and stagnant waters. 

 The largest of the arachnida is the marine species, 

 called the king-crab ; it is common on our Atlantic coasts. 



UNDER SURFACE OF A KING- 

 CRAB (Limulus polyphemus). 



