Versatile Predator Research Articles

Predatory versatility and intraspecific interactions ofSupunna picta(Araneae: Clubionidae)

Abstract Unlike most clubionids, which are nocturnal, drab coloured, hunting spiders, Supunna picta is a highly active diurnal spider with distinctive markings. How this spider interacts with prey and conspecifics was investigated, and the evolutionary significance of this unusual spider’s behaviour is discussed. S. picta is shown to be a versatile predator which not only catches prey cursorially; it also builds a web it uses for detecting prey and invades alien webs where it catches insects and the resident spiders. Unlike some web-invading spiders from other families, S. picta does not use aggressive mimicry when in alien webs. S. picta has a very rapid, erratic style of locomotion which seems to be important in both prey capture and in escape from its own predators. During intraspecific interactions, S. picta performs distinct display behaviours, interactions at and away from webs being similar. Males cohabit with subadult females in webs and mate after they mature. Females make flat, papery egg sacs, more like the egg sacs of many gnaphosid spiders than the typical egg sacs of clubionids.

Predatory versatility and intraspecific interactions of spartaeine jumping spiders (Araneae: Salticidae):Brettus adonis, B. cingulatus, Cyrba algerina, andPhaeaciussp. indet.

Abstract The behaviour of four species (Brettus adonis, B. cingulatus, Phaeacius sp. indet. (Sri Lanka), Cyrba algerina (France & Portugal)) of a primitive salticid subfamily, Spartaeinae, was investigated in the laboratory, and observed in the field. B. adonis, B. cingulatus, and C. algerina were found to be versatile predators. As well as being, like typical salticids, effective cursorial predators of insects, they also invaded alien webs, acted as aggressive mimics by performing a variety of vibratory behaviours, captured and fed on the host spider (araneophagy), and fed on insects (klepto-parasitism) and eggs (oophagy) they found in invaded webs. Phaeacius sp. indet. neither invaded webs nor was an active cursorial predator of insects. Instead, it was a highly eucryptic, sedentary ambushing specialist that sat on tree trunks and lunged downward on passing insects. Although they did not spin prey-capture webs, each of the four species moulted in a silken structure which crudely resembled a web. Cyrba sometimes spun rudimentary enclosing nests somewhat resembling typical salticid nest. Intraspecific interactions of B. cingulatus and C. algerina consisted of visual and postcontact (tactile, chemotactic), but not vibratory, displays. These displays were similar to displays of other salticids. In Cyrba, behaviour that brings legs and palps into lengthy contact with the substratum was well developed and was possibly related to the spider’s heavy reliance on pheromonal communication. Results from this study are discussed in relation to a hypothesis of Jackson & Blest (1982), which proposes that ancestral salticids were web-builders, web-invaders, and aggressive mimics.

The biology ofTaieria erebus(Araneae, Gnaphosidae), an araneophagic spider from New Zealand: Silk utilisation and predatory versatility

Abstract Taieria erebus (Gnaphosidae) was found to be a versatile predator: it captured insects both cursorially (away from webs) and kleptopar-asitically (on alien webs); it captured spiders in both the presence and absence of webs; and it also ate the eggs of host spiders (oophagy). When T. erebus invaded webs, it was as an aggressive mimic — it performed a repertoire of vibratory behaviours to lure the host spider. Although T. erebus pursued and captured spiders on diverse web-types, it was more effective as a predator when invading densely (rather than sparsely) woven cribellate and non-sticky webs, and was especially effective on non-cribellate sticky webs. Gnaphosids are traditionally referred to as hunting spiders, but T. erebus built a small prey-capture web. T. erebus also preyed on segestriid spiders, then used their webs to catch more prey, this being an unusual example of a spider using, as a tool for predation, the spinning-work of another species from an unrelated family. T. erebus used spec...

Capture efficiencies of web‐building jumping spiders (Araneae, Salticidae): Is the jack‐of‐all‐trades the master of none?

According to the ‘Jack‐of‐all‐trades hypothesis’, a specialist predator that uses relatively few discrete predatory behaviours is expected to be highly effective on the few types of prey on which it specializes. A versatile predator, that specializes on these plus additional prey, is expected to be less effective than the specialist predator on the prey they have in common. However, few studies have clearly addressed this hypothesis, especially with respect to behavioural specialization. Portia is a behaviourally complex and aberrant genus of salticid spiders, all studied species of which are cursorial spiders and web‐builders and specialized web‐invading predators that use vibratory aggressive mimicry and feed on the spiders which they deceive. Interspecific and, within P. fimbriata, interpopulational variation occurs in predatory behaviour. ‘Cryptic stalking’, a specialized manner of stalking and capturing other salticids, is unique to P. fimbriata from Queensland, a habitat in which cursorial salticids are superabundant. Otherwise, each studied species and population of Portia uses qualitatively the same repertoire of predatory behaviours (including the same set of vibratory behaviours). Queensland P. fimbriata, having each of the prey‐specific behaviours (‘trades’) of the other Portia plus one more, is more of a jack‐of‐all‐trades. If the postulated trade‐off occurs, then Queensland P. fimbriata would be expected to be less effective than other Portia at using the shared prey‐specific behaviours. Against insect‐prey away from webs, Queensland P. fimbriata had lower capture efficiency than other Portia, apparently supporting the jack‐of‐all‐trades hypothesis; but Queensland P. fimbriata was more, instead of less, efficient as a predator of web spiders, counter to prediction from the hypothesis. Although the jack‐of‐all‐trades hypothesis cannot be viewed as falsified simply on the basis of these findings, the validity of this hypothesis is at least suspect.