HABITS OF SPIDERS. 287 



The abdomen is broad, six-segmented. The chelicerse are chelate, 

 the pedipalps like legs. The legs are extremely long. Respiration is 

 effected by tubular trachea;. 



To avoid multiplying orders (there are enough as it is), I include here 

 the Cyphophthalmidee, which have chelicerae and pedipalps similar to 

 the above, but an eight-segmented abdomen, and the habits of book- 

 scorpions, e.g. , Cyphophthalinus and Gibbocellum. 



Order 6. AraneidjE. Spiders. 



Spiders are found almost everywhere upon the earth, and 

 some are at home in fresh water. Most of them live on the 

 juices of insects, and many form webs in which these are 

 snared. The courtship of spiders is often a very complex 

 affair, and in some cases the males run a great risk of being 

 devoured by their larger and stronger mates. Before stating 

 the peculiarities of structure, we shall briefly consider the 

 spinning and the courtship of spiders. 



Spinning. — At the end of the abdomen there are usually 

 three pairs of spinnerets. Each is a perforated papilla, 

 comparable to the rose of a watering-can, and is connected 

 internally with the tubes of spinning glands. When these 

 glands are compressed a viscid material oozes out from 

 the spinnerets or from some of them. The extremely thin 

 filaments from the tubes of each spinneret unite into a 

 thread, and the thread of one spinneret is often combined 

 with that from the others. In this way a compound thread 

 of exquisite fineness, though rivalled by a quartz fibre, is 

 produced, but two or four separate threads are often exuded 

 at the same time. Before beginning to " spin," the spider 

 often presses the spinnerets against the surface to which the 

 thread is to adhere, and draws the filaments out by slowly 

 moving away. Often, however, the filaments ooze out quite 

 apart from any attachment. The legs are also much used in 

 extending and guiding the thread, and some spiders have on 

 the hind legs a special comb of stiff hairs. 



One of the most important ways in which the secreted 

 threads are used is in forming a web. The common garden- 

 spider {Epeira) makes a web which is a beautful work of 

 art, and very effective as a snare for insects. The spider 

 carries a thread across the selected area and fixes it firmly ; 



