ARACHNIDA 125 



exposure to the atmosphere. Spider's silk is very strong, 

 and yet flexible. It is used by man for several purposes 

 as cross lines in surveyor's instruments, to swing the 

 pendulums of very delicate and accurate clocks. 



It is very interesting to watch an orb- weaver spin its 

 web. First it climbs to some favorable spot and sends a 

 floating strand of silk out on the wind. If the other end 

 catches, the spider runs along the line several times, 

 strengthening the first thread by adding other strands; 

 then goes to the middle of its line, attaches a new strand, 

 and drops to the ground, thus forming a new line from the 

 middle of the first to the ground. By letting go new 

 threads, and dropping down, and scrambling up, a couple 

 of dozen lines are stretched. These meet at a point which 

 is to be the center of the orb. After these " radii" are 

 ready, a continuous spiral is spun from the center outward 

 which forms a series of concentric cross connections between 

 them. An orb-weaver is able to spin two kinds of silk, 

 one of which is covered with little viscid droplets. Finally, 

 two viscid threads are put on the radii between the con- 

 centric curves of the spiral. 



The snare is now ready, and the spider takes position at 

 the center, ready to dart out in any direction. If an awk- 

 ward grasshopper or a careless fly blunders into the web, 

 the viscid threads stick to it until the spider can run out 

 and quiet the struggling victim by swathing it in silk. A 

 spider, crouching at the center of its web, is able to see 

 well in all directions, for there are eight little eyes on the 

 top and front of its head. It is able to observe and pursue 

 its prey with precision. The claws at the tips of the legs 

 are admirably adjusted for running over the web and 

 handling silk threads. Any animal captured is seized in 

 the jaws and the secretion from the poison claws at their 

 tips soon quiets it. 



A spider has a small mouth and cannot eat large 

 pieces of food. It sucks the juices of its victims and casts 

 their shriveled bodies out of its web. At the end of the 



