The biology of Simaetha paetula and S. thoracica, web‐building jumping spiders (Araneae, Salticidae) from Queensland: co‐habitation with social spiders, utilization of silk, predatory behaviour and intraspecific interactions

Abstract

The biology of two aberrant species of salticid spiders is described from observations in tropical Queensland and in the laboratory. Typical salticids are cursorial hunting spiders that do not build prey‐catching webs, although they frequently build enclosing, tubular nests. Simaetha paetula (Kerserling) and S. thoracica Thorell, however, are both cursorial predators that build nests and spiders that build large prey‐catching webs. Nests and webs may be built alone or incorporated into the same structure. Adults, more often than juveniles, build isolated tubular nests. Juveniles, more often than adults, build webs without tubes. Nest‐webs are built most often on leaves and stems of plants, and the leaves are sometimes fastened to stems by strong silk clamps. Intraspecific interactions of S. paetula occur both at and away from nest‐webs. Away from nest‐webs, visual displays occur, but both visual and vibratory displays are important at nest‐webs. A repertoire of discrete displays occurs in both contexts. One prevalent display, clawing, is apparently multi‐channel: visual when the spiders are distant from each other and away from nest‐webs; tactile or chemotactic after the spiders come into contact with each other; and vibratory when they are at nest‐webs. During inter‐male interactions, displays occur that are unusually stereotyped for a salticid and require an unusual degree of co‐ordination of the movements of the two spiders. Males co‐habit in nest‐webs with sub‐adult females and mate when the female matures. Two different copulatory postures are routinely adopted, one of which is aberrant for salticids. Cannibalism is frequent, but the hypothesis that cannibalism reduction has been important in the evolution of display behaviour is not supported. Species of Simaetha Thorell often live within the colonies of the social spider Badumna Candida (L. Koch) as a kleptoparasite, gleaning insects from the edges of the alien webs and incorporating its own nest‐webs within the alien communal web. Although vulnerable to the glue on the social spider webs, Simaetha has behavioural specializations that enable it to avoid becoming prey of the social spiders. The biology of Simaetha is discussed in relation to salticid evolution. 1985 The Zoological Society of London