Foraging by a Predaceous Beetle, Coleomegilla maculata (Coleoptera: Coccinellidae), in a Polyculture: Effects of Plant Density and Diversity

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Abstract
Experimental studies in a greenhouse demonstrated that the foraging rate per individual of a predaceous beetle, Coleomegilla maculata , on egg masses of the European corn borer was significantly reduced by increasing density, but not diversity, of the plants on which it foraged. In higher-density plantings, the beetles apparently spent more time foraging on plants that contained no food, indicating a certain degree of randomness in the foraging behavior of the beetle. These data help explain why observed predation rates on European corn borer egg masses were higher in field plantings of com monocultures than the more densely planted corn-bean-squash polycultures. Since polycultures are nearly always more dense than their respective monocultures, intercropping may act to decrease the predation rate and abundance of certain insect predators or parasites.

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