Cribellate Orb Weaver

This gorgeous little lady is pretty certain to be Uloborus glomosus — one of very few Uloborus species in North America. Spiders in this family are notable for having very long front legs, with little tufts of hair around the far joints; they have a variety of common names, including feather-legged orb weaver and tufted orb weaver. They sit with the forelegs extended, elongating and camouflaging the spider. Camouflage is also provided by the distinctive “horned” abdomen.

Uloborus webs lack sticky strands, instead relying on special tiny, leg-entangling gaps between the strands. This gapped, fuzzy silk is created by an organ called the cribellum, which produces very fine, non-sticky silk which is then combed out by the spider’s leg tufts (“setal brushes” or “calamistra”, or a variety of other names depending on whom you speak to). The silk strands are so tiny and close together they are subject to Van der Waals forces, like the minuscule ridges on the feet of a gecko; the strands’ surface also absorbs waxes from insect “skin” on contact. Together, these actions form a powerful “glue” which does not dry out.

Uloborus species also lack venom; instead of chemically immobilizing the prey, the cribellate orb weaver spider dispatches its victims by wrapping them tightly in silk, constricting them.

Leave a Reply

Your email address will not be published. Required fields are marked *