i8o AMERICAN SPIDERS 



whole series of radii a spiral thread that holds them in place during 

 the subsequent spinning. The turns of this "scaffolding spiral" are 

 wide apart. 



Up to this point all the lines (the foundation, radii, hub, and 

 scaffolding spiral) are of dry silk. They are the framework of the 

 primitive platform. 



Beginning at the outer margin beyond the scaffolding spiral, the 

 spider now puts down viscid spirals upon the dry web skeleton. It 

 is guided, to some extent at least, by the scaffold, by tensions in the 

 lines, by the nearness of outside lines, and by various other factors. 

 Before the full circular turns begin, the spinning may be directed to 

 filling in corners with short curves connecting few radii, or with 

 longer loops that sometimes swing halfway around. As the spider 

 gradually approaches the center, the dry lines of the scaffolding 

 spiral are bitten out, wound up, and discarded, or sometimes eaten. 

 The viscid spirals and loops, ordinarily composed of a single coiled 

 thread from the beginning point to the end near the center of the 

 orb, are placed down with a slow and deliberate motion in a very 

 special manner. The spirals may be spun clockwise or counter- 

 clockwise. 



These sticky lines are composite; they consist of a dry core of 

 two closely joined threads covered evenly on the outside with a 

 viscous film derived from different glands. Following attachment 

 of the compound line to a radius, it is grasped by the claws of one 

 hind leg; these, as the spider's body swings across the space, pre- 

 pare to fix the thread on the next radius. At the same time, the line 

 is grasped near the middle by the claw of the other hind leg, 

 stretched rapidly to half again its length, then let go with a snap. 

 The result is an elastic line that contracts to the width of the space 

 between the radii; upon magnification, it is shown to be beaded 

 with a series of small round drops of sticky silk. The stretching of 

 the silk line breaks up the viscid film and distributes it along the line 

 like beads on a necklace. 



The web is now essentially finished, and the spider returns to 

 the hub, often to alter it in the way characteristic of its group, which 

 consists of biting out the center or ornamenting it in various ways 

 by adding distinctive bands of silk. These bands, decorative loops, 

 or zigzags of thick, white, flossy texture, presumably strengthen 

 the center of the orb; from this attribute they have received the 

 name "stabilmenta." They seem to be vestiges of the early custom 

 of overspinning the central portion to provide a resting space in 



