WEB-SPINNER AT WORK 89 



book, and we replied, fr show us this thing and 

 we will believe." There on the bridge railing, 

 on the rocks projecting over the water and among 

 the branches of the brookside trees, were thou- 

 sands of webs like silvery curtains. We tested 

 them, and lo! it was true. The guy-lines which 

 stretch from one support to another resisted when 

 touched gently with a lead -pencil. The radii 

 behaved in just the same fashion. They neither 

 stretched nor stuck fast. The spiral line did both. 

 We could hardly get the pencil free; the line fol- 

 lowed, stretched to nearly twice its original length. 

 By twisting the pencil we freed it, and the thread 

 sprung back uninjured to its normal position be- 

 tween two radii. 



Here was a fact, or a series of facts, which 

 challenged us. Some thinking must be done, and 

 we half thought, half dreamed the matter out 

 there in the shade. One must begin at the be- 

 ginning; why does the spider make a web? To 

 catch flies, of course, and other insects. From 

 this point it was easy to reason that the spider 

 would get a larger dinner with a sticky web than 

 with a dry one. But why not make all the threads 

 sticky? We had to go back to the spider for 

 that, and found, by experimenting and watching, 

 that it was most important from the spider's point 

 of view that the radii should be dry and inelastic. 

 The web was undoubtedly stronger and more 

 stable for having a framework of inelastic threads 

 tightly stretched from one support to another. 

 Now the wily spider waiting for her prey cannot 



