OHAPTEE V. 



THE ARMATURE OF ORBWEBS : VISCID SPIRALS. 



The Spi- 

 ral Scaf- 

 folding'. 



The next step in orbmaking is to prepare for the spinning of the con- 

 centric lines or spirals. This is done by starting a line at or near the 

 notclied zone and carrying it around spirally toward tire circum- 

 ference, attaching it by the spinnerets to tlie intersected radii. 

 Tliis forms the si>iral scaffolding. The distance between these 

 lines is about equal to the widtli of the notched zone, the space 

 between which and the first scaifold spiral is in fact the free zone. The 

 absolute widtli differs of course according to the size of the web. In large 

 orbs of Epeira domiciliorum from which the explanatory figure (Fig. 77) was 

 drawn, the distance was about an inch between any two of the eight spirals 



(I-VIII) except between I-II, where it was 

 about three-fourths of an inch. These wide 

 sjdrals, as will presently be seen, are the 

 scaffolding upon and by which the true 

 spirals are laid in, and from which they 

 dift'er by being destitute of viscid beads. 



Before the beaded spirals are spun, 

 however, which is the completion of the 

 snare, a preliminary act some- 

 times occurs. Very many orb- 

 webs are not perfect orbs ; in 

 some the entire space circumscribed by the 

 foundation lines and the foliage or other 

 objects to which they are attached, is filled 

 with true viscid spirals, thus nearly elimi- 

 nating the Foundation Space proper. In 

 other orbs only the lower part of the snare is netted with spirals to the 

 very foundation lines. In others again the angles formed by the interior 

 margin of the Foundation Space (the inner foundation lines) represented 

 by letters ix and x, in the figure, are filled with spirals. In such cases 

 these corners or angles have usually been covered first. For example, in 

 the orb at Fig. 77 the animal first spun the spirals which fill up the 

 angle ix. She then passed to the right hand corner x which was in like 



(-9) 



Corner 

 Loops. 



Fic. 77. Spiral scaffolding. Lines I-VIH are 

 the scaffold ; ix, a section filled in ; x, cor- 

 ner loops. 



