Silk mediated defense by an orb web spider against predatory mud-dauber wasps

Stabilimenta are zigzag and spiral designs of seemingly conspicuous silk included at the centers of many spider webs. We examined the association of stabilimenta with the ability of spiders to defend themselves against predatory mud-dauber wasps. We found that Argiope trifasciata (Araneae, Araneidae) were significantly more likely to survive attacks by Chalybion caeruleum and Sceliphron caementarium (Hymenoptera, Sphecidae) when spiders Included stabilimenta in webs. This association could not be explained by factors such as differences in sizes or conditions of spiders nor locations of webs. We suggest that stabilimenta may function to delay pursuit of spiders as they drop from webs by physically blocking wasps, camouflaging spiders or distracting attacking wasps. Stabilimenta may function in a role very similar to the retreats built by many other genera of spiders and appear to be an adaptation to reduce the predation pressure faced by spiders that have evolved foraging habits at highly exposed diurnal web sires.