SPIDERS I I 5 



characterized by their circular outline within which are disposed 

 numerous radii and a series of concentric circular or spiral threads. 

 The circular snare is usually placed within an irregular triangle, 

 or quadrangle, or polygon, which is held in shape and position by 

 stout stay lines extending and fastening to the adjacent branches 

 or fence rails or door frames or whatever serves as frame work for 

 the snare. The webs vary greatly in size, the largest being 

 sometimes a foot and a half to two feet in diameter. The spiders 



which spin these webs are 

 called garden spiders or 

 orb- web weavers, and most 

 of them are highly colored 

 and have a nearly spheri- 

 cal abdomen ( fig. 73 ) . 

 They may be found "hang- 

 ing head downwards usu- 

 ally near the center of the 

 net; others have a retreat 

 near one edge of the net in 

 which they hang back 

 downwards. While resting 

 Fig. 73. Argiope, an orb-weaver. in these retreats they keep 



hold of some of the lines leading from the net so that they can 

 instantly detect any jar caused by an entrapped insect" 



Find one of these orb-webs in good condition, i. e. not torn 

 and ragged but new and complete. Examine it and note the 

 regularity of its construction. Trace the stay-lines to their 

 attachments; note the shape of the outer polygon; note the "spiral 

 zone," i. e. that part of the snare filled with lines laid down in 

 apparently concentric circles; note that these apparently concen- 

 tric circles are not separate circles but are spiral and that the line 

 composing it is continuous; between the outer polygon and the 

 spiral zone there is a region crossed by the radii but without other 



