Searching strategy of the generalist predator Podisus maculiventris (Say) (Heteroptera:Pentatomidae)

Robert Neal Wiedenmann, Purdue University

Abstract

The search strategy, search behavior, and functional response were examined in field and laboratory experiments for females of the stinkbug Podisus maculiventris (Say) (Heteroptera:Pentatomidae). Prey were third-instar larvae of Mexican bean beetle, Epilachna varivestis Mulsant (Coleoptera:Coccinellidae). Field-cage studies were conducted in soybeans from 1986-1988. Predation was measured in 1986-1987 at low prey densities, comparable to latent population levels. Attach rates averaged 0.47 attacks per predator per day, and remained consistent as prey density increased. Low attack rates suggested predators were limited by searching for prey, and consistent attack rates suggested an inverse relationship between search area and prey density. From attack rates, a model was developed to describe search area, using a negative exponential function of prey density. The model was used to predict attack rates when prey were at high, or economic, levels. In the third season, predation was measured at low densities to validate model parameters, and at high densities to test model predictions. Results indicated that the search model predicted predation rates accurately at both low and high prey densities. Since the model was based on behavioral assumptions, predators were observed in the laboratory as they searched for prey. Measured search behavior was consistent with assumptions of random search and relatively short handling times, but did not conclusively test the assumption about predators having information about prey density. The functional response of P. maculiventris was measured in a limited laboratory arena. Results showed a Type II curve, with a maximum of about 9 prey attacked per day at highest prey density. Overall, P. maculiventris appeared to use a search strategy whereby scarce prey were found consistently, long periods were spent resting or plant-feeding, but attack rates were limited by searching requirements. Resting periods may reflect metabolic savings and plant feeding may reflect phytophagous ancestry. The search strategy is appropriate for predators that persist in habitats with scarce prey. The impact of predators like P. maculiventris may occur before pest populations increase, by delaying pest outbreaks and persisting in the crop.

Degree

Ph.D.

Advisors

O'Neil, Purdue University.

Subject Area

Entomology|Ecology|Zoology

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