106 BRANCH ARTHROPODA 



Color. Almost all spiders are covered with hair. The color 

 is partly in the skin and partly in the hair. The most common 

 colors are grays and browns, but the colors are very varied, and 

 in some species, as the jumping spider, they are almost as 

 bright and gorgeous as those of butterflies. 



Foods and Feeding. They are generally carnivorous, sucking 

 the juices from their prey. Some spiders spin webs, others do 

 not. The spider's thread is composed of many fine threads, 

 each passing from the body by a separate tube and then unit- 

 ing. The united thread forms a cord finer than the finest silk 

 of the silkworm, hence it is often used for the " cross-hairs " 

 of the telescope. 



Respiration is by lungs or lung-sacs containing bookleaf- 

 like plates, and by tracheae. 



Senses. The sense of sight is well developed, but they seem 

 to be shortsighted, seeing clearly only at a distance of 4 or 5 

 inches. The palpi are organs of touch. 



Dimorphism. Male spiders usually have longer legs and 

 smaller bodies than the females. 



Sub-order Tet'r&pneu'mones. These spiders have four lungs 

 and eight eyes. The most important members of the group 

 spring upon their prey, often catching mice and small birds 

 (Fig. 78). The large, dark, hairy spiders (Myg'ale) found in 

 bunches of bananas belong here. The claws of the mandibles 

 or jaws work up and down instead of from side to side. 



The trapdoor spiders (Cteni'zd) of the Southwest dig tunnels 

 in the soil, line them with silk, and cover them with a close- 

 fitting hinged lid. 



Sub-order Dipneu'mones. The members of this sub-order 

 have two lungs and a pair of tracheae. This group includes 

 the majority of living spiders. 



The ground spiders (Dros'sw/rr) do not spin a web, but hunt their prey 

 at night. Many species make silken tubes in which they lay their eggs or 

 hide when molting or in winter. An eastern species lives in a bag of silk 

 hidden under stones. 



The tube-weavers (Clubion'ida-) . These are also species which spin no 

 web. In summer they live in flat, tubular nests on plants, sometimes 

 in rolled leaves. In winter they live in tubular nests under bark and 

 stones. 



The Funnel Web Weavers (Agaleriid<r). They weave a concave sheet 

 of silk with a funnel-like tube on one side, and with threads extending in 



