2 04 



FIRST LESSONS IN ZOOLOGY 



then the spiral ones (fig. 164). Two sets of spiral lines 

 are put in, a first set, which is made fi-om the center out- 

 wards, is not sticky, and serves as scaffolding upon which 

 the spider works when putting in the second set. The 

 latter is sticky and is put in from the outer part of the web 



toward the center. The tem- 

 porary spiral or scaffolding is 

 torn out as the work of put- 

 ting in the sticky permanent 

 spiral progresses. The web 

 building includes a great deal 

 of interesting behavior on the 

 part of the spider, the delicate 

 manipulation of the viscid 

 lines, and the almost geomet- 

 rically accurate disposition of 

 the lines composing the snare, 

 combining to render the whole 

 performance little short of 

 marvellous. 



There are other kinds of 

 webs spun by other kinds of 

 spiders. Indeed among the 

 orb-\\'eavers alone there is a 

 great variety in the character 

 of the webs; some, for ex- 

 ample, lack a sector of the 

 circle, being otherwise con- 



t'lG. 165 —A lon^'-lc!;(4i'(l s|iidri 

 Tetragnatha sp . (in its \v(_*l 

 (Une-halfiiatunilsizc; frum lilc. 



structed on regular orb-web plan ; others are composed 

 of perhaps less than one-half a circle, although still with 

 radii, and with concentric arcs of circles in place of com- 

 plete circles in the spiral zone. Certain kinds of spiders 

 spin a peculiar broad line, or rather band, of curling silk, 

 which leads from tlie snare to the side retreat. Or thc\- 

 make of this band of curled silk a central zone not com- 



