150 AMERICAN SPIDERS 



web from a surface to an aerial station was a relatively simple step. 

 The orb web of Uloborus lies most often horizontal, or slightly 

 inclined, and is only rarely the vertical structure of the typical orb 

 weavers. The horizontal position is a less favorable one, dependent 

 for success on insects that fly upward against it or drop down upon 

 it; whereas the vertical web can intercept much larger flying fauna. 



Featherfoot Spiders. As has been noted, the curious spiders of 

 the genus Uloborus are most numerous in the tropics of the world, 

 relatively few varieties occurring in the north. Several distinct 

 species are found in the southern United States, but only one, 

 Uloborus americamis, appropriately named the "featherfoot spider" 

 (see Plate XXIV), is common all over the United States and in south- 

 ern Canada. This uloborid has a carapace longer than broad, which 

 is provided in front with eight eyes, in two rows, whose small size 

 confirms the slight reliance this aerial creature places on eyesight. 

 Its chelicerae are moderately robust, but no venom glands are asso- 

 ciated with them a condition almost unknown in other spiders, 

 and suggesting that the sicky spiral of the orb web and the jaws 

 of the spider are adequate to quiet its prey. The long front legs are 

 often curved, in many species being provided with the tufts of 

 feathery hairs that are the source of their common name. The abdo- 

 men is often surmounted with humps and bedecked with pencils 

 of hairs. A pronounced variation in coloration is characteristic, and 

 pale white, speckled, lined, or all black specimens are often found 

 in the same species. 



The relatively small orb webs of the featherfoot spider, four or 

 five inches in diameter, are usually placed close to the ground in 

 moist, shaded situations on low bushes and underbrush, on dead 

 sticks, in hollow stumps, or among rocks. The invariably horizontal 

 web is composed of the same elements as that of the typical orb 

 weavers: foundation lines, radii, dry spiral scaffolding, and a con- 

 centric series of sticky spirals. Before laying down these latter, 

 Uloborus spins a typical preliminary spiral scaffold of dry silk that 

 is used as a bridge to the next radius. The spirals are a composite oi 

 viscid and dry threads, as in the Argiopidae, but here the sticky 

 material is carded from the cribellum with the aid of the very regu- 

 lar row of calamistral hairs on the fourth metatarsus. The spider 

 has never depended on artistic perfection for its capturing snare, 

 but rather on the sticky lines, and close examination shows that the 

 web is imperfect in many respects. Quite often it is most unsym- 



