Genus-specificity of araneophagy of linyphiid spiders and species of other families (Arachnida, Araneae)

We found genus specificity of predation by spiders on other spiders in captivity which surpass them in body size (araneophagy). Adult specimens of three species of the linyphiid genus Walckenaeria which were successively tested for araneophagy (in the laboratory) in the order of first species discovery in the field in their natural habitat, showed a consistently high level of killing potential (predation on allospecific spiders which surpassed them in body size: genus-specific araneophagy of high intensity). The body size was measured by prosoma size on the dorsal side without the chelicerae, and by average leg length and average leg thickness. This consistently high genus-specific araneophagy of Walckenaeria was not shown by eight other linyphiid genera. In three other spider families than linyphiids where at least two species per genus could be tested (Theridiidae, Araneidae, Clubionidae; adult females of the genera Theridion, Steatoda, Larinioides, and Clubiona) also showed a consistently high level of predation on allospecific spiders surpassing them in size as the genus Walckenaeria had shown. Apart from the genera-dependent capacity to kill large spiders, there were differences between the adult males and females in their killing capacity. In the theridiids, araneids, and clubionids, i.e. in non-linyphiid genera, only females managed to kill allospecific spiders surpassing them in size, whereas in Walckenaeria the males could do this in two out of the three tested species. We conclude that high araneophagic capacity is significantly less genus-specific across nine genera of the linyphiid family than across four genera of three other spider families (theridiids, araneids, and clubionids).