The Role of Learning In An Insect Predator-Prey Relationship
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Previous research has shown that larval antlions, Mrymeleon crudelis Walker, a type of sit-and-wait predator, are capable of using a learned cue to anticipate the arrival of prey before they fall down the steep sides of the antlions’ conical pits. Ants, a common prey item of the antlion, have developed an anti-predator tactic to the antlions’ sit-and-wait predatory strategy, namely a highly sophisticated form of rescue behavior. Ants will attempt to rescue nestmates struggling on the of the pit and also may injure antlions in the process. This experiment investigated whether antlions could anticipate ant rescue by associating a learned vibratory “rescue” cue with removal of a prey item from the pit, and discriminate this cue from another, different, vibratory cue paired with uninterrupted feeding. Thirty-two antlions were assigned to the Learning (LRN) (n = 16) or Control (CTL) (n = 16) groups. The LRN group was exposed to a vibratory cue paired with an uninterrupted feeding opportunity and a different vibratory cue paired with “rescue,” when the antlion received no food. The CTL group experienced randomization of vibratory cues and feeding or “rescue” events. Pit volumes, feeding and sand-throwing behaviors were recorded for the 40 days of the experiment. During “rescue” trials, LRN antlions decreased their rate of sand-throwing during the vibratory cue more than antlions in the control condition, whereas during feeding trials no difference between rates of sand throwing of LRN and CTL antlions was detected. This finding suggests that antlions used learned cues to anticipate that struggling prey would be rescued and changed their rate of sand-throwing to reflect the anticipated outcome of a prey event.