THE AERIAL WEB SPINNERS 185 



their plight hopeless by their struggles, which bind the many lines 

 together into strong bands. The use to which the silk of this spider 

 has been put by primitive peoples and its failure as commercial 

 silk have been noted. 



Our only silk spider is Nephila clavipes (Plate 10), a long- 

 bodied, olive-brown species with lighter spots on the abdomen and 

 long legs provided with thick brushes of conspicuous black hairs. 

 Now largely confined to the extreme southern states, this Nephila 

 was probably the same one that lived much farther north at Floris- 

 sant, Colorado, during Oligocene times. The bodies of the older 

 females are fully an inch long, specimens from the tropics often far 

 larger. The quarter-inch-long male is less than one percent of the 

 female's bulk. 



The orb webs of Nephila are not replaced as frequently as those 

 of other orb weavers, since they have features that make them far 

 more permanent. The dry spiral scaffolding line is looped back 

 and forth, and is a permanent part of the web. The radii are numer- 

 ous; they are branched so that the interval at the outside of the web 

 is little more than near the center. The viscid spirals are loops for 

 the most part, only rarely complete circles. The hub is eccentric, 

 and is located high up near the side of the web. 



The ray spiders of the family Theridiosomatinae are small, 

 globose orb weavers, which have diverged rather sharply from the 

 more typical members of the group, and seem to lie in the vague 

 intermediate zone between the three principal families of aerial 

 spiders. Our best-known species is the widely distributed Theridio- 

 soma radiosa, once believed to be the same as a species found in 

 Europe. Females run about one tenth of an inch long, and have 

 rounded, oval, highly arched abdomens marked with many small 

 silvery spots. The remarkable egg sac, a brownish, pear-shaped 

 bag, is suspended by a long, often forked thread from the branches 

 of trees or the sides of stones. The aerial station makes it immune 

 to depredation by crawling insects. 



The ray spider is commonest in dark, damp situations, and 

 favors shaded woods, the underbrush along streams, and nooks at 

 the base of cliffs. The web, usually vertical in position and three to 

 five inches in diameter, is a most remarkable structure. It is first 

 spun as a reasonably typical orb snare with a meshed hub and sev- 

 eral spiral turns in the notched zone, then the hub and these threads 

 are bitten out. The radii, a dozen or so in number, are next rear- 

 ranged so that they converge upon a small number of lines that 



