108 



BRANCH ARTHROPODA 



The crab spiders (Thomis'idt?} are so-called because of their short broad 

 form and peculiar habit of walking sidewise or backward. " They spin 

 no webs, but lie in wait for their prey." 1 Some brightly colored species 

 conceal themselves in flowers. Their protective resemblance is so good 

 that insects visiting the flower often light within reach of the spider before 

 seeing it. They live about plants and fences and hibernate in winter under 

 stones and bark. 



The jumping spiders (At'lidce) have stout bodies and short logs, bright 

 colors, and conspicuous eyes. They jump quickly sidewise or backward 

 for a long distance. They make no webs except those in which they hiber- 

 nate or lay their eggs. 



The Running Spiders (Lycos' ides). These are the familiar hairy dark- 

 colored spiders found under stones and logs. They depend upon their 

 speed for the capture of their prey and run very swiftly. They resemble 

 in appearance and habits the so-called tarantulas of the Southwest, but are 

 smaller. The claws of their mandibles move horizontally. Their eyes are 



Fig. 79. Female spider with young ones. (Cooper.) 



of different sizes. Some of these spiders build tubular nests in the ground 

 and line them with silk. They sometimes conceal the entrance with leaves 

 and sticks. They often drag the egg-sac, a large gray ball, after them. In 

 genus Lyco'sa the young (Fig. 79) climb upon then* mother's back. The 

 female of another genus, Dolome'des, carries the egg-sac " in her mandibles 

 until the young are ready to hatch, when she fastens the sac in a bush and 

 spins a web of irregular thread about it in which the young remain for a 

 time." 



Order Acari'na. These arachnids have stout bodies, there 

 being no apparent segments, the abdomen being united with the 

 cephalothorax. There is no heart nor blood-vessels. The res- 

 piration is performed by means of tracheae. They are generally 

 oviparous; some are viviparous. Many are parasitic (Fig. 80). 



1 Comstock. 



