What is the function of 'pre-dispersal' behavior in juvenile social spiders (Stegodyphus dumicola: Eresidae)?

Bridging and ballooning dispersal in spiders are preceded by "tiptoe" behavior, in which the spider stands on the tips of its eight tarsi, with the legs extended downward and the abdomen raised, and releases one or more silk lines. The occurrence of tiptoe behavior has been used in experiments to indicate a propensity to initiate dispersal. Juvenile social spiders Stegodyphus dumicola Pocock 1898 (Eresidae) exhibited tiptoe behavior while walking along the upper strands of the capture web at night. Simultaneously, they released long silk lines that streamed upward. These behaviors were not followed by dispersal. In wind-tunnel tests we found that tiptoe behavior increased with time during the evening activity period and occurred with higher frequency in small individuals. We suggest that tiptoe behavior in juveniles of S. dumicola is not associated with dispersal, but is more likely a component of web-building.