Parasitoid behaviour: predicting field from laboratory

1. Most of what is known about parasitoid behaviour comes from laboratory observations: field quantitative observations on searching parasitoids are extremely difficult to do and are rare. The basic components of Aphytis melinus’s response to California red scale (Aonidiella aurantii) were studied in the laboratory: encounter, rejection, drumming, probing, oviposition, and hostfeeding. It was then asked whether these observations provided a reliable guide to behaviour in the field in a situation that was very different from the laboratory. 2. Field observations were carried out on bark on the trunk and interior branches of trees where live scale density is extremely high in patches, dead scale make up 90% of all scale, and could be expected to interfere with Aphytis search. 3. The laboratory observations predicted well the time taken in the field for each basic event (drumming or probing) and average times spent on a scale. Also well predicted were the distributions of times spent on drumming, probing, and total time on a scale. Rejection rates were much higher in the field. Thus, the laboratory studies predicted foraging behaviour in the field with variable success; potential explanations for observed mismatch between laboratory and field and its possible larger implications are discussed.