(JEXERAL CHARACTERISTICS OF ORBWE AVERS SNARES. 



57 



FIG. 54. The ribbon brace of Acrosoma. 



movements there, always when capturing an insect, and often in bringing 

 the captive to the Hub, do at times result in the marring and breakage 

 of the snare. The fact that the prey are taken to the centre to be fed 

 upon and sometimes to complete the swathing is a reason why that por- 

 tion of the web should not be covered with viscid beads, which are obvi- 

 ously a hinderance to feeding upon and 

 swathing the victim. In fact the viscid 

 parts have to be cut out in order to per- 

 mit the revolving of the captured prey 

 when it is being swathed. 



2. Moreover, the struggles of insects en- 

 snared upon the beaded spirals, and subse- 

 quent actions of the spider to capture its 

 prey, invariably break up more or less of 

 the web. In the case of large insects the 

 damage done is quite serious. Were the 

 Central space also beaded it is evident 

 that the very seat and throne of the 

 aranead at the hub of the snare would 

 be greatly liable to invasion, to her sore discomfort and disadvantage, 

 especially in cutting off her avenues of approach to the main portions 

 of the snare. This would be no less true in cases where her retreat 

 is a leafy or silken castle outside the limits of the orb but connected with 

 the hub by a trapline. The breaking of the radii at the point of their 



attachment to the hub of course must cause all 

 the connected parts towards the circumference 

 to relax, entangle, and drop away. Repair in 

 such cases is difficult or impossible. The far- 

 ther from the centre is the point at which the 

 insect is entangled, the less injury ensues, the 

 longer does the web remain serviceable, and 

 the more easily is it mended. Thus, the ab- 

 sence of beads from the entire Central space 

 gives added security to the snare. 



3. In like manner the economy of the Free 

 zone may be considered as protective. The ab- 



Fi-i. 55. Semicircular rigzag cords in gence Q f sp i ra l \i nes enables many insects to 

 the hub of Argiope. * 



pass quite through the net, with little or no 



impediment. When there is a momentary arrest or entanglement, the 

 subsequent escape or capture is accompanied by very slight, if any, de- 

 struction. 



4. Here, too, it may be observed that the necessity for viscid beads near 

 the centre is not as manifest as upon the outlying parts. The momentary 

 pause caused by an insect striking upon the naked radii of the Free zone 



