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Coexistence is thought to be based mainly on interspecific differences in the use of limiting resources and habitat choice, both being associated with specific traits. We studied morphological parameters within an assemblage of large wandering spider species in Costa Rica subdivided into three subguilds: (1) semi-aquatic species, (2) forestground dwellers and (3) vegetation dwellers. We hypothesized that the observed differences between the spider species in microhabitat preferences and abilities to adhere to smooth surfaces should be associated with corresponding morphological traits. The leg scopulation patterns were surprisingly complex and reflected the ecological preferences of the spiders. We found that the scopulation patterns and the ratio of tarsus to leg length (T/L) appeared to be most important: the poor adhesion abilities of the semi-aquatic species were reflected by the absence of tarsal claw tufts, and these species also showed the highest T/L ratio. The forest-ground dwellers had smaller claw tufts relative to body mass than the vegetation dwellers that consistently showed the best adhesion performance. This study presents the first family-spanning ecomorphological analysis of an assemblage of large tropical wandering spiders. [ABSTRACT FROM AUTHOR]

An unsuspected attachment mechanism may help these huge spiders to avoid catastrophic falls. Spiders spin silk from specialized structures known as abdominal spinnerets--a defining feature of the creatures--and this is deployed to capture prey, protect themselves, reproduce and disperse. Here we show that zebra tarantulas (Aphonopelma seemanni) from Costa Rica also secrete silk from their feet to provide adhesion during locomotion, enabling these spiders to cling to smooth vertical surfaces. Our discovery that silk is produced by the feet provides a new perspective on the origin and diversification of spider silk.