i 7 6 AMERICAN SPIDERS 



engineering triumph, a fixed geometrical object that symbolizes 

 spider and partially allays unreasoning distrust of the creature. To 

 poets of all times, the orb, divorced from the spinner itself, is a 

 celestial creation founded on beauty, its graceful spirals symbolic 

 of the heavens and its mystery, its fragile lines a measure of the 

 evanescence of life. To the evolutionist, it is only the last step of 

 a series that has resulted in a circular design an inevitable shape; 

 and the spider has no more to do with spinning such a symmetrical 

 web than "a crystal has with being regular." The orb web, among 

 all objects produced by lesser creatures an unrivaled masterpiece, 

 is above everything a superb snare. Contemplating it, one echoes 

 the words of the meditative Fabre: "What refinement of art for a 

 mess of Flies!" 



The orb web, quickly strung up and as quickly replaced when 

 defective, brings to the trapper an abundance of the choicest flying 

 insects. It exploits a food supply that is active both by day and 

 night, and, in the adult winged state, available only by chance to 

 other aerial spinners. Almost invisible in ordinary light, the lines 

 stretch across space as a tough but yielding net, into which fliers 

 blunder, to be held by sticky, elastic threads that make the most 

 powerful wings ineffective. (That a similar trap, produced by a 

 like series of instinctive actions, should have evolved among a sep- 

 arate line of spiders might well seem an impossibility. Nevertheless, 

 the cribellate uloborids have fashioned a web that, except for sub- 

 stitution of the hackled band for the beaded spiral lines, is a faithful 

 reproduction of the snare of the orb weavers.) 



This most highly evolved of all aerial webs is the result of the 

 random activities of aerial prototypes, which finally established 

 order among the irregular lines in the horizontal platform. During 

 most of its history, the flat snare was enclosed in the original maze 

 of crossed threads. At first the lines of the platform intersected 

 haphazardly to form an irregular framework made of dry dragline 

 silk spun from the same glands as in modern forms. Over this skel- 

 eton was laid a covering silk produced by different glands and 

 dispensed through the posterior spinnerets, with which were mixed 

 draglines from the ever active front spinnerets. These two elements, 

 the framework and the covering, remain discrete throughout the 

 evolution of the aerial flat snares. 



This definite pattern underlies the sheet web of the linyphiids, 

 even though the finished sheet may not appear to be based on a 

 definite plan. These weavers begin at the center of the dome, put 



