Search

Predators that prey on dangerous species have evolved effective capture traits. In spiders, venom and silk represent distinct substances associated with prey capture. However, the use of such adaptations comes at a cost. Based on a possible trade-off, the use of only one effective capture mechanism should be optimized if a predator is to specialize on a single type of dangerous prey. We investigated hunting strategies in two Callilepis spp. and one Nomisia species, Nomisia exornata, closely related ant-eating spiders from the family Gnaphosidae. We hypothesized that specialized Callilepis spiders would adopt a more stereotyped capture strategy compared with less specialized Nomisia. We also expected that Callilepis would rely on only one subjugation mechanism. To test this, we compared their hunting efficacy and hunting strategies, with an emphasis on venom vs. silk utilization. Nomisia restrained ants with silk (then bit them), whereas Callilepis relied solely on its venom. This was also reflected in trophic traits connected with silk and venom utilization; Callilepis had larger venom glands than Nomisia, whereas Nomisia had more piriform silk glands than Callilepis. Callilepis was more effective because it subdued prey more quickly, presumably owing to ant-specific venom. Callilepis and Nomisia handled ants from two subfamilies with different degrees of success; Callilepis was more successful with Formicinae ants, whereas Nomisia handled Myrmicinae ants better. We show that sole reliance on venom allows Callilepis to be more efficient in overcoming ants than Nomisia, which uses both silk and venom. However, such specific adaptations might restrict specialized predators from exploiting alternative prey. [ABSTRACT FROM AUTHOR]

Adult male ladybird spiders (Eresus spp. Araneae: Eresidae) possess conspicuous red and black coloration. As these spiders are palatable to many predators, they are likely to be Batesian mimics of some other, defended species. We therefore aimed to identify potential models of two ladybird spider species, the spring-breeding Eresus moravicus and the autumn-breeding Eresus kollari, by assessing the co-occurence and similarity of the spiders and their putative models. The abundance of potential models of Eresus spp. was monitored at nine sites where the spiders are found. Phenotypic similarity between the spiders and their potential models was assessed by comparing their colour, coloration pattern, and body size and shape. The ladybirds Coccinella septempunctata and Hippodamia variegata co-occurred with Eresus spp. at most sites during the whole season and were among the most abundant species found; the leafhopper Cercopis sanguinolenta was common only in spring and the stink bug Graphosoma lineatum only in late summer and early autumn. Analyses of similarity showed that coccinellids, including Coccinella septempunctata, were relatively similar to Eresus spp. We conclude that the seven-spot ladybird beetle Coccinella septempunctata is probably the key model of the ladybird spiders. Other taxa may serve as secondary models, further enhancing the spiders' defence against predators. [ABSTRACT FROM AUTHOR]