Three hundred forty female jewel wasps were reared as larvae on blowfly pupae and then separately exposed as adults to varying numbers and combinations of previously parasitized and unparasitized housefly pupae. Each adult was tested with 6 fresh housefly pupae. Only foraging experience on unparasitized housefly pupae increased host acceptance for subsequent housefly pupae, producing curvilinear and convex host-acceptance functions; foraging experience on preparasitized housefly pupae had no effect upon subsequent host acceptance. Labile host- acceptance thresholds are thus adjusted by foraging experience to track local unparasitized host abundances for different species by modulating host-species cue response biases. These presum- ably kairomonal response biases were found to be sensitive to psychophysical “subjective proba- bilities of stimulus presentation,” representing expected unparasitized host-species encounter rates, not altered “payoff matrices” of “observer decision outcomes,” representing modified host- species profitabilities.
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