THE SPIDER 



105 



Compound eyes and antennae are absent, and so we see that 

 spiders are very unlike insects. The first pair of mouth 

 appendages are called cheli'cerw and end in claws, at whose 

 apices the poison-glands open to the exterior. The K(>cond 

 pair of mouth parts, called pedipalps, are long and seem to 

 take the place of antennae. Near the stalk of the abdomen 

 on the ventral side is a pair of slits 

 which open into two lung sacs. In 

 a few spiders there is a second pair 

 of slits ; such spiders have four 

 lung sacs. 



All spiders spin a nest, but all do 

 not spin webs. The large webs 

 that attract our notice are the per- 

 fected product in the evolution 

 of spinning. The most primitive 

 spiders appear to be those that 

 burrow in the earth and line their 

 tubes with silk. Such spiders are 

 known as tunnel-weavers. They are found in our Southwest- 

 ern States and are commonly known as trap-door spiders. The 

 hd of the tube or tunnel is made of drj' clay and is penetrated 

 through and through by the spun silk. When the hd is closed, it 

 looks exactly like the ground around it, so that the opening is easily 

 overlooked. Some of these spiders acquire great size (Fig. 106) . 



A step in advance is seen in the tube-weavers (Fig. 107). 

 The tube-weavers spin in the grass their tubes of silk, at the 

 bottom of which they live, while at the outer end they build 

 over the grass a platform, which serves them mainly as a trap 

 for jumping insects. Such are the webs that one sees in the 

 grass on a dewy morning (Fig. 108). 



Fig. 107. — Agalena, the com- 

 mon grass spider. Nat. size. 

 Photo, by W. H. C. P. 



