76 



AMERICAN SPIDERS AND THEIR SPINNINGWORK. 



passed down 1 and along D to 3, where attachment was made, and radius 

 3 was formed. Once more the centre was sought, and passing along the 

 line A the point 4 was reached and another radius there fastened. Thus 

 on from 4 to 5, from 5 to 6, and so around the entire circle. The mechan- 

 ical advantage of this order is apparent. Several times the central termini 

 of the radii were strengthened by lapping threads across them. 



This tendency to alternate apposition I have frequently observed in 

 various species, and its character will be better shown by giving several 



other schemes of the order of progression in spinning radii. The 

 jjg^i ' schemes do not present a complete sequence of the radii from 



the very beginning, but number from the point at which I hap- 

 pened to catch the spider at work. They are to be read as in Fig. 72, the 

 order of numerals showing the relative position of the radial lines in the 

 order of their spinning. The series will show, I think, that while no abso- 

 lute mathematical regularity marks the succession, some method of alterna- 

 tion evidently dominates the spider's movements. She knows the necessity 



11 



10 



FIG. 73. The order of spinning 

 in twelve radii. Epeira ver- 

 tebrata. 



FIG. 74. Order of inserting 

 nine radii. 



ra 

 FIG. 75. Order of six radii. 



FIG. 76. Order of 

 five radii. 



which exists for balancing such a peculiar and delicate structure, and 

 adopts her mode of spinning to the exigencies of her spinningwork. 



Blackwall states that after the completion of the radii the spider pro- 

 ceeds to the centre, turns around and pulls each radius with her feet to 

 ascertain its strength, breaking such as are defective, and replacing them 

 by others. I have never seen anything of the kind ; the spider in settling 

 herself and gathering the radial lines into her eight claws naturally jerks 

 them somewhat. But no such purpose was ever suggested to my mind as 

 that declared by Blackwall. He also says that the radii are composed of 

 double lines, a statement which my observations contradict. 1 I have seen 

 very many radii spun, but have never observed any one overlaid or doubled 

 (if that be the meaning) as is often the case with foundation lines. On 

 the contrary they were always composed of one thread drawn out in the 

 usual way from the spinning spools. 



Rennie in his remarks upon the construction of an orbweb expresses 

 the opinion that the most remarkable circumstance in the process is that 



Nets of the Geometric Spiders, page 182. 



