The Attentive Spider: Search-Image Use by a Mosquito-Eating Predator

Evarcha culicivora, a jumping spider from East Africa, feeds indirectly on vertebrate blood by choosing blood-carrying female mosquitoes as prey.It also has an unusually complex mate-choice system. Here, we show that both sexes of E. culicivora can use mate-finding search images and also use prey-finding search images. In experiments, individuals were primed by seeing blood-carrying mosquitoes, primed by seeing potential mates or not primed (control: saw neither). They were then introduced into an arena where the task was to find a blood-carrying mosquito or a potential mate. In all instances, the prey or potential mates were dead individuals used as lures. The lure in the arena was either cryptic (i.e. hidden behind nylon netting and accompanied by distractors) or conspicuous (i.e. netting and distractors absent). When lures were conspicuous, the identity of the priming stimulus appeared to be irrelevant.However, when lures were cryptic, significantly more spiders found the lure that was congruent with the priming stimulus and significantly fewer spiders found the lure that was incongruent with the priming stimulus. On this basis, we conclude that the spiders were using search images for finding the lures and that search images were relevant only when the lure to be found was cryptic