COSTS AND BENEFITS OF FACULTATIVE AGGREGATING BEHAVIOR IN THE ORB-SPINNING SPIDER GASTERACANTHA-MINAX THORELL (ARANEAE, ARANEIDAE)

The potential costs and benefits of foraging in aggregations are exami ned for the orb-spinning spider Gasteracantha minax. Web-site tenacity is low in this species; individuals frequently move among sites, ther eby joining aggregations of different sizes. Female spiders in aggrega tions suffered lower predation rates and attracted more males than the ir solitary counterparts. However, aggregated eggsacs, probably produc ed by females in aggregations, experienced higher rates of parasitism than solitary eggsacs. We found no evidence of higher prey capture suc cess rates among spiders in aggregations. However, we demonstrate a no vel way in which spiders can increase their foraging efficiency by dec reasing silk investment. A spider spinning a web within an existing ag gregation can attach the support threads of its web to those of other webs, thereby exploiting the silk produced by other spiders.