oO 



AMERICAN HPIDEKS AND THEIR SPINNINCiWOltK. 



Free 

 Zone. 



overlays the radius longitudinally for a minute space at the point of 

 crossing. The precise effect of this arrangement may be produced thus : 

 Stretch a cord tightly; tlien take a second cord, loop it by one twist 



around the first, and draw its two loose ends 

 in opjiosite directions. The appearance of these 

 notches is sliown at Fig. 53. 



The Free Zone (FZ, Fig. 49, see also Fig. 

 oO), the third division of the Central space, is 

 tliat portion of the orb which, for the 

 nicst part, lies between the notclied 

 zone and the spirals, and consists 

 simjily of the radii without any crossing lines. 

 Its outer boundary apjiears always to be marked 

 by the last or innermost of the foundation 

 spirals. Black wall' objects to the statement 

 of Kirby and Spence concerning a free zone 

 as characteristic of geometric webs, that this 

 is true of but one species. But the greater 

 [)art of our vertical orl)s have the free zone. 

 It seems strange that Blackwall- should speak 

 of the nets which are destitute of the free zone 

 FK..52. Sheeted hub of Argiope. ^^ having the Centre entirely clo.sed up (meslied 



hub), for certainly in America the orbs spun by the genus Epeira, which 

 are by far the most frequent, have both the closed centre and the free 

 zone, almost invariablj'. (See Fig. 50.) I must doubt tlie accuracy at 

 this point of the distinguished observer, and the 

 doubt is confirmed by my limited ob.servation of 



the si)inningwork of British spiders.^ 



sec rpj^^ economy of the Central Space in 



Space ^^^ several juirts must be a matter of 



conjecture, but there are some good 

 grounds for the following opinions : — 



1. It must be noted, first, that no part of the 

 Central space has viscid beads. This permits tlie 

 freer motion of tlie spider around the centre 

 Avithout liability of entanglement upon her own snare. She is, indeed, 

 able to run over the beaded spiral space with apparent impunity, yet her 



' " On the Construction of the Xets of Geometric Spiders," Zoological Journal, Vol. V., 

 1832-4, page 184. 



- As above, page l.S,3. 



' Mr. Cecil Warl)iirton writes me from Soiithiinrt, 10iit;lanil, that the .snares (if .Meta 

 scgmentata are distin^uishalile at a glance from tho.se of most common English Kpeiruids, 

 a.s Zilla atrica, Epeira diademata, Ep. quadrata, etc., liy the jiresence of a notched zone 

 and the absence of a niesiicd i-eutre. EviiU'iilly, Ins nbservation of the connnun sju'cics 

 showed a closed centre. 



.53. Notched spirals igreatly en- 

 larged). 



