Superfamily Argiopoidea 



viscid spiral. The diameter of the orb is from two and one half 

 to five inches. It is usually vertical or slightly inclined; in a few 

 cases it is horizontal. 



The rays converge upon a trapline, which usually extends per- 

 pendicular to the plane of the orb; but a convenient point of 



Fig. 416. WEB OF THERIDIOSOMA RADIOSA 



attachment may lead the spider to stretch this line in another 

 direction. The spider rests upon the rays at the centre of the 

 web, with its dorsal aspect uppermost and its head away from the 

 orb, and, by pulling on the trapline with its fore feet, pulls the 

 orb into the shape of a cone or funnel (Fig. 416). It is in this 

 position that the spider waits for its prey. When an insect 

 becomes entangled in the web, the spider releases its hold on 

 the trapline allowing the web to spring back. This springing 

 of the web, as in the case of the triangle spider, increases the 

 probability of the insect becoming more firmly ensnared. 



I have seen a ray-spider finish its web, the web being partly 

 made when the observations began. There was a spiral guy-line 

 as in the web of orb-weavers; but the spider cut out the whole of 

 the guy-line leaving no hub. In one case the spider fastened three 

 radii together so as to form a "ray," each radius at first extending 

 clear to the centre. 



The egg-sac (Fig. 417) is light brown, pear-shaped, and about 

 one eighth inch in its transverse diameter. It is suspended by a 

 thread, which is usually forked. The pointed end of the egg-sac to 

 which this thread is attached is a separable cap, which is partly 

 pushed off when the spiderlings emerge, as shown in the figure. 



404 



