Speculative hunting by an araneophagic salticid spider

Portia fimbriata, an araneophagic jumping spider (Salticidae), makes undire cted leaps (erratic leaping with no particular target bring evident) in the presence of chemical cues from Jacksonoides queenslandicus, another saltic id and a common prey of P. fimbriata. Whether undirected leaping by P. fimb riata functions as hunting by speculation is investigated experimentally. O ur first hypothesis, that undirected leaps provoke movement by J, queenslan dicus, was investigated using living Fl fimbriata and three types of lures made from dead, dry arthropods (P. fimbriata, J. queenslandicus and Musca d omestica). When a living P. fimbriata made undirected leaps or a spring-dri ven device made the lures suddenly move up and down, simulating undirected leaping, J. queenslandicus responded by waving its palps and starting to wa lk. There was no statistical evidence that the species from which the lure was made influenced J. queenslandicus' response in these tests. Our second hypothesis, that J. queenslandicus reveals its location to P. fimbriata by moving, was investigated by recording P: fimbriata's reaction to J. queensl andicus when J. queenslandicus reacted to lures simulating undirected leapi ng. In these tests, P. fimbriata responded by turning toward J. queenslandi cus and waving its palps.