The Structure and Habits of Spiders. 17 



which will be described in another chapter. 

 There are three pairs of them ; but many- 

 spiders close them together when not in use, 

 so as to cover up the middle pair. The third 

 pair of spinnerets are often several-jointed, 

 and extend out behind the body like two tails. 

 In front of the spinnerets is a little open- 

 ing, Fig. r, K, which leads to air-tubes that give 

 off branches to different parts of the abdomen. 

 At M, Fig. 1, are usually two colored bands, or 

 rows of spots, marking the course of muscles 

 attached to the skin at various points along 

 these lines. 



Fig. 4 is the back of the same spider. The 

 head is not separated from the rest of the body, 

 as in insects, but forms, with the thorax, one 

 piece. On the front of the head are eight eyes, 

 O, which are differently arranged in different 

 spiders'. At the back part of the thorax is a 

 groove, P, under which is attached a muscle 

 for moving the sucking-stomach, Fig. 5, d. 

 From this point radiate shallow grooves, that 

 follow the divisions between the muscles of the 

 legs. On the abdomen are several pairs of 

 dark smooth spots, which mark the ends of 



