SPIDERS AND THEIR IVEB-MAKING 



203 



spider, if it has no side retreat, usually rests. Touch one 

 of the radii or one of the foundation lines with a pencil 

 point ; touch the spiral with a pencil ; a difference in the 

 character of the two kinds of lines is at once manifest. 

 The spiral thread is "sticky," the radii and foundation 

 lines are not so ; the web is made of two kinds of silk. 

 If a bit of the spiral line be examined under a magnifier 

 it will be seen that, ranged along the silken thread, like 

 beads on a string, are many tiny globules or drops. These 

 are a sticky, viscous sort of silk, which does not dry and 

 harden as the usual silk does. These sticky drops make 



Fig. 164. — How the spider " swings round the circle " in putting in the 



spiral line; Ri 16 = radii i to 16; J, scaffolding line, to be torn 



out; X, the spider in various positions. The spider crawls and drops 

 along the course indicated by the dotted line, holding the new sticky 

 line free from the old one. (After McCook.) 



the spiral line much more effective as a snare. Throw an 

 insect into the web and observe the behavior of the spider. 

 If possible observe the spinning of an orb-web. A 

 bridge which has a metal or wooden fretwork on each 

 side affords a particularly good place to watch this. In 

 the square or diamond-shaped open spaces the spider can 

 be readily seen at work. It works in a regular way, put- 

 ting in first the foundation (fig. 163), and radial hnes, and 



