Predation in diversified agroecosystems: relations between a coccinellid predator Coleomegilla maculata and its food.

Abundance of Coleomegilla maculata (Coleoptera: Coccinellidae) was higher on corn in monocultures than on corn in two different polycultures. Predation rate by the beetle on egg masses of the European corn borer Ostrinia nubilalis was higher in monocultures. Important alternative resources for the beetle in these systems were aphids and pollen. Temporal dispersion of pollen and aphids was more even and species richness of the aphids was greater in the polyculture, while overall density of corn pollen and aphids was greater and their spatial distribution more even in the monoculture. The higher density of evenly spaced food rewards in the corn monoculture had the greatest impact on beetle behaviour, resulting in decreased emigration and therefore greater abundance.-from Authors