128 



ABTHROPODA 



or plates of tissue, in which the blood circulates to give 

 off its carbon dioxide and take up oxygen necessary for 

 the life of every part of the body. 



The spiders are divided into two groups, the spinners, 

 or sedentary spiders, and 

 the non-spinners, or wander- 

 ing spiders. Of the spinners 

 there are four kinds. 



The tunnel weavers are 

 those which make tubes in 

 the earth and line them 

 with silk. Some such as the 

 trapdoor spiders of Texas 

 and California have suffi- 

 cient skill to make a door to 

 close the entrance against 

 intruders. 



The tube weavers make 

 the webs so conspicuous 

 in the grass on a dewy 

 morning. At one side of 

 the web a tube extends 

 toward the ground. Some 

 of these species spin quite 

 deserted buildings and in 



FIG. 147. Photograph of the nest of a 

 Texas trapdoor spider with the door 

 open to the left. 



Of 



dense webs in corners 

 bushes. 



The line weavers are those which construct irregular 

 webs known as cobwebs. 



The orb weavers work with mathematical precision, spin- 

 ning spirals supported by numerous radii. The male orb- 

 weaving spider is much smaller than the female which 



