Prey selection of orb-web spiders (Araneidae) on field margins

In this study, prey composition and numbers of prey ingested by orb-web spiders (actual prey), as well as the food resources available in the habitat (potential prey), the retention efficiency of spider webs, and the prey selectivity of spiders, which bias the prey composition, were investigated for the garden spider Araneus diadematus and the wasp-like spider Argiope bruennichi in two field margin habitats in Bavaria, South Germany. The potential prey of both spider species on field margins consisted of a few flying prey taxa with a dominance of Diptera. In spider webs, mobile Diptera and some Hymenoptera were underestimated whereas small, broad-winged prey items such as Sternorrhyncha were overestimated compared to the composition of potential prey. Spiders avoided prey groups armed with strong mandibles or stings, such as Coleoptera and some Hymenoptera. A mean number of nine prey items in 7 h was consumed by orb-web spiders in field margin habitats consisting mainly of Diptera and herbivorous pest groups such as Sternorrhyncha.