The first impression of a featherlegged orbweaver is of a small oval blob with a tiny, curved “twig” protruding from one end (when the forelegs are held together), or of a tiny V-shaped twig (when the forelegs are held apart). The general colors of this small, hairy spider are drab: white, yellow, gray, tan, brown, or black, and the camouflage pattern varied. The abdomen is arched, with the highest point of the hump toward the front of the abdomen and having two moundlike tubercles, one on each side. Females have conspicuous brushlike plumes of hair on the tibia segment of the elongated, heavier first pair of legs.
This species belongs to a family of spiders called the cribellate orbweavers (Uloboridae). This family is unique in North America because its members completely lack venom. And what does “cribellate” mean? A cribellum is a sievelike plate in front of the spinnerets that causes the silk that emerges from the spinnerets to be “hackled,” or covered with woolly fibers that help snag prey (instead of the sticky threads many other spiders use).
Although a number of spider families include at least some cribellate species, this cribellate family is unusual because its members spin orb (wheel-shaped) webs. Cribellate spiders are not closely related to the true orbweavers, family Araneidae, and most spider families that possess a cribellum do not create circular orbs.
So the featherlegged orbweaver, with other members of its family, is an oddity: it lacks venom, it produces woolly threads instead of sticky ones, and it spins orb webs.
Egg sacs are elongated on one end, slightly spiraled, and have minute spines; they resemble the shape of a whelk shell. Females create linear chains of these egg sacs and typically rest at one end of the chain, forelegs outstretched, looking like just another segment of the chain; the whole impression is of a line of detritus. Also, this species often spins stabilimenta (silken ribbons forming zigzags, lines, or spirals) in the web.
Similar species: There are many other members of genus Uloborus, but most of them live in the tropics. This is the only common member of its genus in our region. Trashline orbweavers (genus Cyclosa, in the true orbweaver family) hide in their orb webs amid a vertical line made of detritus (empty husks of prey insects), with the egg sacs positioned at the hub. The abdomen of trashline orbweavers is typically conical, pointed upward (not downward) at the tip, which extends well past the spinnerets.