ARTHROPODA 85 



which the thread of the spider's web is spun. 

 The venom of the spider is not a fable ; spiders 

 have poison-glands with 

 ducts which open on the 

 tops of the chelicerae. 

 They dispose of their prey 

 by sucking it ; they do not 

 swallow solid food. The 

 habits and webs of spiders 

 are familiar to every one: 

 their nests, as a rule, are 

 only noticed by close ob- 

 servers. The nest is made 

 of spun threads closely 

 felted together to form a 

 round hollow ball. This 

 the house-spiders hang on 

 a wall or among the rafters 

 'of a roof. There are, how- 

 ever, spiders which build 

 their nests under ground; 

 and in this case the nest 

 may be conveniently fur- 

 nished with a lid, which 

 can be pushed up when the 

 animal wishes to come out. 

 Fig. 20 shows the nest of 

 the Trap-door Spider, so 

 called from the construc- 

 tion of its nest. 



Fig. 21 shows a spider- 

 like animal which, at first 

 sight, seems to have five 

 pairs of legs. In fact, how- 

 ever, it has only three pairs, thus approaching the 

 insects in structure. These three pairs of legs 



