246 Nature's Geometricians [FOURTH WEEK 



Leaving behind the old-fashioned horseshoe crabs to 

 feel their way slowly over the bottom of the sea, the spiders 

 have won for themselves on land a place high above the 

 mites, ticks, and daddy-long-legs, and in their high devel- 

 opment and intricate powers of resource they yield not 

 even to the ants and bees. 



Nature has provided spiders with an organ filled always 

 with liquid which, on being exposed to the air, hardens, 

 and can be drawn out into the slender threads we know 

 as cobweb. The silkworm encases its body with a mile 

 or more of gleaming silk, but there its usefulness is ended 

 as far as the silkworm is concerned. But spiders have 

 found a hundred uses for their cordage, some of which 

 are startlingly similar to human inventions. 



Those spiders which burrow in the earth hang their 

 tunnels with silken tapestries impervious to wet, which at 

 the same time act as lining to the tube. Then the en- 

 trance may be a trap-door of soil and silk, hinged with 

 strong silken threads; or in the turret spiders which are 

 found in our fields there is reared a tiny tower of leaves 

 or twigs bound together with silk. Who of us has not 

 teased the inmate by pushing a bent straw into his strong- 

 hold and awaiting his furious onslaught upon the innocent 

 stalk! 



A list of all the uses of cobwebs would take more space 

 than we can spare; but of these the most familiar is the 

 snare set for unwary flies, the wonderfully ingenious webs 

 which sparkle with dew among the grasses or stretch from 

 bush to bush. The framework is of strong webbing and 

 upon this is closely woven the sticky spiral which is so 



