Prey of selected epigeic velvet spiders (Araneae: Eresidae)

The natural prey of spiders has been studied in only a few species, which limits our understanding of their role in ecosystems. Eresid spiders often have a hidden lifestyle; thus, their ecology is still poorly understood. Here we investigated the natural prey of four species of ground-dwelling eresid spiders from Israel - Adonea fimbriata, Dorceus fastuosus, Eresus sp., and Loureedia annulipes - and one (Eresus kollari) from Central Europe. In the last species, we studied the prey in more detail: we compared the natural with the potential prey and investigated prey acceptance using six prey types (Blattodea, Coleoptera, Hemiptera, Hymenoptera, Isopoda, and Orthoptera) under semi-field conditions. The natural prey was studied by analysing the exoskeleton remains of prey found in the webs. We found that the prey composition in the webs differed significantly among species, though two insect groups, beetles and ants, dominated in all eresid species. Among beetles, tenebrionids were the most frequent in eresid species from Israel, while carabids dominated in E. kollari. Beside these beetles, weevils were frequent prey in all examined species. The index of the trophic niche breadth was narrow in all examined species, indicating trophic specialisation; however, feeding trials revealed that E. kollari accepted a wide variety of prey types, showing that it is a generalist opportunistic predator. All eresid species studied here appear to be stenophagous generalists, capturing mainly beetles and ants.