186 AMERICAN SPIDERS 



radiate from a point at or near the center. These rays, in turn, con- 

 verge upon a short trap line that is attached to a convenient twig 

 or surface. The spider rests its body on the rays or the orb, and, 

 sitting upright and facing away from the snare while holding the 

 slack line loosely between its front legs, pulls the web into the 

 shape of a cone or funnel or an umbrella turned inside out, as 

 McCook described it. When an insect strikes the web, the spider 

 lets go the line; and both snare and spider spring back to aid in 

 the further entanglement of the victim. Only one of the rays, com- 

 prising three or four radii, is badly damaged with each capture; so 

 the spider uses the trap several times. 



The upright position is most unusual for an aerial spider. It is 

 made possible by the spider sitting upon a foot basket of taut lines 

 and clinging with its hind legs. The resemblance of this device to 

 that of the triangle spider is most striking. Hyptiotes uses a single 

 sector, hangs back-downward from the ray threads, and springs 

 forward on the line when the trap is released. A single capture 

 destroys the triangular snare, but Theridiosoma has several sectors 

 in reserve. 



In the subfamily Argiopinae are handsome orb weavers second 

 only to the silk spiders in size, and far better known, especially in 

 the North, where their bright colors and large webs make them 

 conspicuous creatures. More closely allied to the typical orb 

 weavers than to the groups already mentioned, the Argiopinae differ 

 from these former in having the posterior eye row strongly curved 

 backward. The typical web of Argiope, the principal genus and 

 the only one that will be discussed here, is ordinarily somewhat in- 

 clined, but may be nearly vertical. It is provided with a sheeted 

 hub. Frequently the web is accompanied by a tangle of lines be- 

 hind the orb, the so-called "barrier web," and less occasionally by a 

 thinner tangle in front. These are probably vestiges of the stopping 

 mazes of the primitive orb weavers; as was the case with these pro- 

 totypes, they provide a protective screen against some enemies. At 

 the center of the web is a stabilmentum consisting of a zigzag band 

 of white silk in nearly vertical position, usually occupying a third 

 of the diameter of the orb. In some instances it is vaguely indi- 

 cated, but ordinarily it is a conspicuous mark, a signature of this 

 group of spinners. The spider hangs at the hub, head-downward as 

 usual, with the legs at each side of the stabilmentum; by appropriate 

 stimulation it can be induced to shake the web vigorously (as do 

 the long-legged cellar spiders and many orb weavers) until it be- 

 comes an indistinct blur. The males are very much smaller, about 



