Potential fitness consequences of associative learning in a parasitoid wasp

Several studies have documented associative learning in insects, but the adaptive value of such learning is not yet well understood. To evaluate this issue, we quantified long-term fitness consequences of associative learning in the parasitoid wasp, Biosteres arisanus. We compared individual wasps that were allowed to choose host substrate based on experience (“learning” wasps) to wasps that could only make random substrate choice (“random” wasps) in an environment where only one out of two substrates contained host eggs. In two experiments, the average number of host eggs parasitized and offspring produced were significantly larger for learning than for random wasps. Our results allow detailed examination of the conditions under which learning would have positive fitness effects in ecological systems similar to ours. These conditions include relatively long search duration for hosts; the ability to remember a learned preference over extended periods of interfering activities; and large mean differences between alternatives, and small variances, which together allow rapid evaluation of alternatives and long duration of exploiting the superior one.