viii INTRODUCTIOxN 



" Catalogue of the Described Araneae of Temperate North 

 America," by George Marx, in the Proceedings of tJie United 

 States XationalMnseum, 1890, which is a useful index to what 

 has been published on American spiders. 



The front half of a spider's body, called the cephalothorax, 

 contains in one piece the head and thorax, the only outward 

 division between them being shallow grooves from the middle 

 of the back to the front legs. In the middle of the cephalo- 

 thorax is usually a groove or depression, under which, inside, 

 is a muscle that moves the sucking apparatus by which food is 

 drawn into the mouth. At the sides of the thoracic part are 

 four pairs of legs, and on the head part are a pair of palpi 

 and a pair of mandibles. The legs have seven joints: (i) the 

 coxa, the thick basal joint, having little motion; (2) the tro- 

 chanter, a short joint moving very freely on the end of the 

 coxa ; (3) the femur, the largest joint of the leg, moving with 

 the trochanter in all directions; (4) the patella, moving up and 

 down on the end of the femur; (5) the tibia, joined closely to 

 the patella and moving with it up and down ; (6) the meta- 

 tarsus ; and (7) the tarsus, moving together on the end of the 

 tibia. The -pa1pj are like small legs and have one less joint 

 than the walking legs. The mandibles are close together at 

 the front of the head (fig. 2). They are two-jointed, the basal 

 joint stout and the end joint or claw slender and sharp-pointed. 

 The claw has near its point a small hole, which is the outlet 

 of the poison gland. The poison kills or disables the insects 

 which are captured by the spider. Its effect on the human 

 skin varies in different persons ; sometimes it has no effect at 

 all ; oftener it causes some soreness and itching like the stings 

 of mosquitoes and bees, and cases have been known in which it 

 caused serious inflammation which lasted a long time. Spiders 

 seldom bite, and only in defense, the bites so commonly charged 

 to them being often the work of other animals. 



