12 The Structure and Habits of Spiders. 



spider ; Fig. 4, the upper side ; and Fig. 5, an 

 imaginary section through the body, to show 

 the arrangement of the internal organs. To 

 begin with Fig. I : the body is seen to be di- 

 vided into two parts, connected only by the nar- 

 row joint, A, just behind the last pair of legs. 

 The front half of the body, called the thorax, 

 contains the stomach, the central part of the 

 nervous system, and the large muscles which 

 work the legs and jaws. The hinder half, the 

 abdomen, contains the intestine, the breathing- 

 organs, the principal circulating-vessels, the or- 

 gans of reproduction, and the spinning-organs. 

 Connected with the thorax are six pairs of 

 limbs, four pairs of legs, B B B B, a pair of 

 palpi, C, and a pair of mandibles, D. 



LEGS. 



The legs are used chiefly for running, jump- 

 ing, and climbing ; but the front pair serve often 

 as feelers, being held up before the body while 

 the spider walks steadily enough on the other 

 six. One or both of the hinder legs are used to 

 guide the thread in spinning ; the spider at the 

 same time walking or climbing about with the 



