Influence of background and prey orientation on an ambushing predator's decisions

Phaeacius, a sit-and-wait jumping spider, is shown to base predatory decisions on simultaneous use of information about whether the background is matching or contrasting, whether or not the prey has good eyesight and whether the prey is oriented face on or facing away. In prey-choice testing in which mounts (dead prey in lifelike posture on a cork) were used, background and prey orientation influenced Phaeacius' behaviour specifically when a salticid came into view, salticids being prey with exceptionally good eyesight. When the prey was a non-salticid spider or an insect, Phaeacius' behaviour did not vary significantly with background or with prey orientation. In prey-reaction experiments, background and orientation influenced prey behaviour when the prey was a salticid, but not when it was a non-salticid spider or an insect. Phaeacius evidently takes special precautions to minimize the risk of being seen by a prey that has exceptional eyesight.