HOMES AND DOMESTIC HABITS 959 
145. Spiders.—Most spiders spin silken cocoons or sacs 
in which to deposit their eggs. Some spiders carry this 
egg-filled cocoon about with them for the sake of protect- 
ing the eggs. After hatching, the spiderlings remain in the 
cocoon a short time, feeding on each other! Thus only the 
Fie. 156.—Sea-nrchins living in holes bored into rocks of the seashore below high- 
tide line. 
strongest survive and issue from the cocoon to earn their 
living in the outer world. With certain species of spiders 
the young after hatching leave the cocoon and gather on 
the back of the mother and are carried about by her for 
some time. In connection with their webs or snares many 
spiders have silken tunnels or tubes in which to lie hidden, 
a sort of sheltering nest. Those spiders that live on the 
ground make for themselves cylindrical burrows or holes 
in the ground, usually lined with silk, in which they hide 
when not hunting for food. Especially interesting among 
the many kinds of these spider nests are the burrows of 
the various trap-door spiders. These spiders are common 
in California and some other far Western States. The bur. 
