Ondřej Michálek (1), Yael Lubin (2) & Stano Pekár (1)
(1) Department of Botany and Zoology, Faculty of Science, Masaryk University, Brno, Czech Republic
(2) The Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel
Many spiders use silk not only to build prey-catching webs but also retreats (nests). However, even these seemingly defended fortresses can be invaded by specialized predators. For example, some araneophagous spiders use aggressive mimicry and by imitating the vibrations of the caught prey or a potential mate they deceive and hunt the web-building spiders. The ground spider Poecilochroa senilis (Araneae: Gnaphosidae) has been found occasionally in the retreats or webs of other spiders in the Negev desert (Israel). Our aim was to investigate the preference of P. senilis for spider prey and to test the hypothesis of aggressive mimicry, i.e. abuse of signals when invading shelters of other spiders. First, we investigated the fundamental trophic niche of P. senilis by performing acceptance experiments in the lab. We revealed P. senilis accepted only some prey types, mainly spiders. Poecilochroa senilis was able to subdue even spiders bigger than itself. Then we investigated the hunting strategies of P. senilis in a series of behavioural experiments. We used the jumping spider, Mogrus logunovi (Araneae: Salticidae) as a prey, which is commonly preyed upon in the field. Poecilochroa senilis immobilised prey by spraying piriform silk on its face. This strategy is commonly used by gnaphosid spiders to hunt dangerous prey. When invading the shelter of the jumping spider, P. senilis did not utilize stealth or deceiving approach, but directly invaded the shelter through its entrance. The jumping spider frequently abandoned the shelter, but P. senilis remained inside and waited for its eventual return. In other cases, the jumping spider defended the shelter, but P. senilis was sometimes able to penetrate this defence by force. Our observations show P. senilis is an araneophagous predator immobilising its prey by gluey silk. We did not observe use of aggressive mimicry, but P. senilis used conditional hunting strategies to hunt salticids both outside and inside their retreats.
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Ondřej Michálek, Yael Lubin & Stano Pekár