346 ARACHNIDA ARANEAE CHAP. 



Two stout bridge-lines thus constructed will form the upper 

 and lower boundaries of the net. The lateral limits are easily 

 formed by cross lines between them at a convenient distance 

 apart. The spider chooses a point, say, on the upper bridge-line, 

 fixes its thread there, and carries it round to the lower line, where 

 it is hauled taut and firmly attached. Two such cross-lines give, 

 with the bridge-lines, an irregular four-sided figure within which 

 to stretch the snare, and now the work is perfectly straight- 

 forward, and can proceed without interruption. 



Attention is first paid to the radii of the circular web. The 

 first radii are formed by drawing cross-lines within the frame- 

 work in the same manner as before, but the spider carefully 

 attaches these where they intersect by a small flossy mass of silk, 

 and this central point or hub becomes the basis of its subsequent 

 operations. It is a simple matter to add new radial lines by 

 walking from the centre along one of those already formed and 

 fixing the thread to some new point of the circumference. 

 They are not laid down in any invariable order, but with a kind 

 of alternation which has the general effect of keeping the strain 

 on every side fairly equal. Almost every time the spider reaches 

 the centre it slowly revolves, uniting the radii afresh at their 

 point of junction, and increasing the strength and complexity of 

 the hub. It also occasionally digresses so far as to stretch the 

 whole structure by bracing the framework at additional points, so 

 that it loses its four-sided form and becomes polygonal. We 

 have now a number of spokes connecting a central hub with an 

 irregular circumference. 



The hub is next surrounded by what Dr. M'Cook calls a 

 " notched zone," consisting of a few turns of spiral thread which 

 serve to bind more firmly the spokes of the wheel. The most 

 important part of the work is still to be performed. The lines 

 hitherto laid down are perfectly dry and free from viscidity, so 

 that an entangled insect would easily be able to free itself. A 

 viscid spiral line remains to be spun, and the snare will be com- 

 plete. The precise method of laying this down will vary some- 

 what according to the species, but, to refer again to the large 

 Garden-spider, the proceeding is as follows : Commencing at a 

 point somewhat outside the notched zone, the creature rapidly 

 works in a spiral thread of ordinary silk with the successive turns 

 rather far apart. This forms a kind of scaffolding, by clinging 



