Prey discrimination by a generalist coccinellid predator: effect of prey age or parasitism?

1. Patterns of prey discrimination by the generalist predatory coccinellid Coleomegilla maculata lengi Timb. (Coleoptera: Coccinellidae) were studied in relation to prey quality, under laboratory conditions. 2. Choice experiments were performed in which second- and fourth-instar coc cinellids had the choice between Trichoplusia ni (Lepidoptera: Noctuidae) e ggs that were young or old, unparasitised or parasitised by Trichogramma ev anescens Westwood (Hymenoptera: Trichogrammatidae). 3. Coleomegilla maculata larvae did not exhibit any preference for parasiti sed or unparasitised eggs at a similar stage of development but always pref erred younger eggs, regardless of whether or not they were parasitised. Fur thermore, the percentage of rejection was higher and handling time longer o n the less preferred egg type. Pre-imaginal development time, food intake t o reach adulthood, and survival of coccinellid immatures were altered when coccinellid larvae were fed with parasitised and old unparasitised eggs. 4. These results indicate that C. maculata larvae select eggs based on thei r stage of development regardless of parasitism, and that prey quality of a ged prey is lower. 5. Fourth-instar coccinellid larvae spent less time in patches containing s olely parasitised old eggs, and their level of exploitation was greatly red uced, compared with homogeneous patches containing unparasitised young eggs . This suggests that C. maculata larvae respond to variable patch quality b y using flexible decision rules that reflect the payoff of the patch.