SPIDER FLEXIBLY CHOOSES AGGRESSIVE MIMICRY SIGNALS FOR DIFFERENT PREYBY TRIAL AND ERROR

Portia is a jumping spider that invades other spiders' webs, makes vib ratory signals that deceive the resident spider (aggressive mimicry), then attacks and eats the spider. Portia exploits a wide range of prey -spider species. Evidence is provided from observation and experimenta tion that Portia uses a trial-and-error method as part of its strategy for deriving appropriate signals for different prey. To use this meth od, Portia first broadcasts an array of different signals, then narrow s to particular signals as a consequence of feedback from the prey spi der. Feedback can be web vibration or seeing spiders move, or both. Th is appears to be an example of deception involving at least a limited form of learning, an uncommon phenomenon in invertebrates.