76 



AMERICAN SPIDERS AND THEIR SPINNXNGWORK. 



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

 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 aroinid the entire circle. The mechan- 

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

 of the radii were strengthened by lapping threads across them. 



This tendency to alternate apposition I liave 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 

 Order of gpijgj-j-^gg ^Jq ^q^ present a complete sequence of the radii fiom 



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

 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 alternu- 

 titju eviilently dominates the spider's movements. She knows the necessity 



74. Order of inserting 

 nine radii. 



Fii:. 75. Orderof six radii. 



Fiii.76. Orderof 

 five radii. 



Flii. 73. Theorder of spinning 

 in twelve radii. Epeira ver- 

 tebrata. 



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

 adopts her mode of spinning to tlie 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 sucli 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. ^ 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 contraiy they were always composed of one thread drawn out in (he 

 usual way from the spiiming spools. 



Kennie in his remarks ujjon the con.struction of an orbweb expresses 

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



^ Nets of the Geometric Spiders, page 182. 



