242 FIELD ZOOLOGY. 



holding on to the walls of the burrow with the hind pairs of 

 legs; and travelers say that one may more easily pull 

 the lid off the hinge than to pull a spider loose while 

 she is thus guarding her burrow. 



The sense of sight seems to be but feebly developed 

 in spiders, but they appear to be very sensitive to light 

 as opposed to darkness. Spiders have no compound 

 eyes, but have instead an unusual number of simple eyes, 

 eight in most of the families. The object moving is 

 pictured in quick succession by the numerous simple eyes, 

 and the spider quickly takes the alarm and runs away. 

 Whether spiders hear or smell is not known; at least there 

 appears to be no unmistakable evidence of the fact. 



The habit of spinning for trapping food would dis- 

 tinguish spiders from insects if there were no other 

 distinguishing traits. Many of the lepidopterous insects 

 spin cocoons when ready to pupate, and the cocoon of 

 the silk- worm is made of gossamer-fine threads; other 

 insects can spin some sort of a pupal case, and some 

 worms will let themselves down out of harm's way by a 

 spun thread. But as a means of gaining a livelihood, and 

 as spinners of threads consisting of still finer strands 

 drawn into one composite thread, the spiders are unique. 

 The uses made of this spun silk are numerous. They use 

 it in making linings for their nests, in making the sacks in 

 which the eggs are to be stored, and in making traps of 

 various shapes and sorts in which to catch their prey. 

 Frequently the spider mends its web by tearing out the 

 dirty or torn piece and, at the same time, spinning in new 

 threads. 



Webs are stretched in various places. The garden 

 spider always places its web vertically. The house spider 

 spins her web in the comer of the attic or the stable, or 



