Stabilimenta on the webs of Uloborus diversus (Araneae: Uloboridae) and other spiders


  • William G. Eberhard

    1. Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, U.S.A.
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      Universidad del Valle, Departamento de Biologia, Cali, Colombia, South America.


Uloborus diversus places extra silk (“stabilimenta”) near the hubs of its webs, preferentially on short radii ending near anchor threads. Spiders probably distinguish these radii from others by their relatively low extensibility. The stabilimentum probably functions as a camouflage device, and the orientation of the stabilimentum lines probably aids disturbed spiders in making quick exits from webs. Turning responses at radius-frame junctions during these exits are influenced by thread angles at the junctions (and possibly by other factors), and also enable disturbed spiders to reach hiding places quickly. The available data on other stabilimentum-building spiders suggests that they also use stabilimenta to provide defence against visually-hunting predators.