Attention please! Tuft decorations and barrier webs of the spiny spider Thelacantha brevispinamay function to warn off avian predators.
Most studies on spider web decorations have focused on the cruciate decorations of Argiope spiders. Relevant studies on silk tuft web decorations built by spiny spiders are few. The E.Asian spiny spiders Thelacantha brevispinaplace silk tuft decorations on a 3D barrier web. In this study, we investigated how barrier webs and silk tuft decorations are involved in prey capture and predator defense of T. brevispina. The field experiments were conducted in a tropical island in southern Taiwan. The presence of barrier webs and the color signal of silk tuft decorations were manipulated by painting tuft decorations so they are indistinguishable to the background, and removing the barrier web with burning incense. Therefore there are two treatments: (1) decorations painted, (2) no barrier, (3) control. The interaction between Thelacantha brevispinaand its prey and predators were recorded by video cameras. Interception of prey was higher in webs without barriers than the control webs, but interception of prey in painted decorations was similar to control webs. Silk tuft decorations on barrier webs, therefore, come at a foraging cost. For all treatment groups wasps approached but never attacked the spiny spiders. However, bird predation occurred on spiders in webs with painted decorations. These results suggest that wasps are not the major predator of spiny spiders and silk tuft decorations and barrier webs of T. brevipina function to warn off avian predators.
更新：Mar-10-2014 01:22:51 (Taiwan, GMT+08:00).