x INTRODUCTION 



insects which they eat, at a distance of four or five inches, but 

 beyond that do not seem to see anything clearly. At the ends 

 of the feet are two claws, curved and with teeth along the inner 

 edge, and in many spiders there is a third shorter claw between 

 them (fig. 212). The claws are sometimes surrounded by a 

 brush of flattened hairs (figs. 104, 1 14). The basal joints of the 

 palpi are flattened and have their inner edges extended forward 

 so that they can be used as jaws to press or chew the food. 

 These are called the maxillae. Between the maxillae is a small 

 piece called the labium, and between the legs is a larger oval 

 piece called the sternum. 



The hinder half of the body, the abdomen, is connected with 

 the cephalothorax by a narrow stem (fig. 1). It has at the 

 hinder end the spinnerets, three pairs of appendages having 

 at their ends a great number of microscopic tubes through 

 which the thread is drawn out. When not in use the spin- 

 nerets are folded together, so that the smaller inner pair are 

 concealed. 



The thread of spiders resembles that spun by caterpillars in 

 making their cocoons, and can be manufactured in the same 

 way into silk cloth. The spider's thread is composed of a great 

 number of finer threads passing from the body through separate 

 tubes and uniting into one before they have time to dry. This 

 can be seen by examining the attachments of spiders' threads 

 to glass. All the spinning tubes are not alike, but on certain 

 parts of the spinnerets are larger or differently shaped tubes, 

 and these are the outlets of glands of different kinds in the 

 spider's abdomen, and are used in making different kinds of 

 threads for certain parts of the webs, nests, or cocoons. 



In front of the spinnerets on the under side is a small 

 opening to the tracheae, or air-tubes (fig. 1). At the front 

 of the abdomen on the under side is a transverse fold of the 

 skin, at the ends of which are the openings of the air-sacs or 



