Costs and benefits of facultative aggregating behaviour in the orb-spinning spider Gasteracantha minax Thorell (Araneae: Araneidae)

The potential costs and benefits of foraging in aggregations are examined for the orb‐spinning spider Gasteracantha minax. Web‐site tenacity is low in this species; individuals frequently move among sites, thereby joining aggregations of different sizes. Female spiders in aggregations suffered lower predation rates and attracted more males than their solitary counterparts. However, aggregated eggsacs, probably produced by females in aggregations, experienced higher rates of parasitism than solitary eggsacs. We found no evidence of higher prey capture success rates among spiders in aggregations. However, we demonstrate a novel way in which spiders can increase their foraging efficiency by decreasing silk investment. A spider spinning a web within an existing aggregation can attach the support threads of its web to those of other webs, thereby exploiting the silk produced by other spiders.