86 AMKincAX Sl'lDKKS AND THEIR SPINNINGWORK. 



made with a rapidity which often prevents the eye from following the 

 motions of the foot and spinnerets. 



When the innermost spiral is reached tlic araiiead swings or strides to 

 tlic linh, takes up her position head downward and hites out the flossy 

 guidon, wliicli she takes within her mouth. ^ Whether or not it is finally 

 rejected I cannot say, but it is certainly retained for some time, and I 

 believe is dissolved within her mouth, and swallowed. 



What becomes of tiie unbeaded scaffold lines which the spider uses for 

 weaving in her system of beaded sjtirals ? They are not seen among the 

 concentrics when the orb is tini.shed, and the secret of their dis- 

 Spiral ai)pearance is only to be unfolded by watc'hing the architect as 

 R ved ^^^^ proceeds with her work. It will thus be found that as she 

 spins her way frc^m the outer margin toward the centri' she 

 bites off her scaffolding and permits it to drop away, rolling it u}) usually 

 within her jaws. It has served her purpose by giving her footing while 

 engaged in forming the essential i)art of her structure, and when she 

 needs it no longer she removes it, precisely as the mason when " point- 

 ing" his stonework takes down his wooden scaffold as he works from the 

 top toward the bottom of his wall. I have observed this process repeat- 

 edly, as others have done.^ Mr. Emerton^ speaks of " a few turns in the 

 centre" apparently confounding what I have called the "notched zone" 

 with the special scaffolding, as his figure also shows. The latter is 

 not simply a continuation of the former, but is ratlier an independent and 

 permanent j)art of the orb, having a wholly different use and is separate- 

 ly spun. Blackwall says that the " imiermost circle" of the spiral scaffold 

 is permitted to remain; but my observations, on the contrary, are that all 

 the concentrics are removed and the beaded spirals carried to the very 

 margin of the free zone. Possibly the habit is not invariable in its 

 details ; and on the whole presents a good example of intelligent exercise 

 of the sj)inning function. 



II. 



The efticiency of an orbweb for the capture of prey depends chiefly 

 upon its viscidity and strength. The former quality pertains to the spiral 



lines which differ from the other parts of the web in Ijeing 

 Spiral covered at close intervals with minute viscid beads. To these 



the value of the snare as an instrument is chiefly due, for they 

 adhere to and melt upon the wings, limbs, and hairs on the bodies of 

 insects that strike the web, and thus fatally entangle them. Rennie has 



' Kirliy and Piience, Introduction to Entomology, page 413, are quite correct in their allusion 

 to this fact, but tlie biting away of the cotton like tuft is not necessarily accompanied by 

 the opening up of the hull. Blackwall sugL'csti'd tlie prolialily true reason M'hy tlie central 

 space is without viscid l)eads. 



^ Blackwall, op. cit., page 18,'!. 



' Emerton, American Naturalist, ii., 478 ; I'ackard's (luide, page 040 ; .Structure and I laliiLs 

 of Spiders, page 04. 



