Searching Strategy of the Predator Podisus maculiventris (Say) (Heteroptera: Pentatomidae)

Abstract

Predation rates for the predator Podisus maculiventris (Say) on third-instar Epilachna varivestis Mulsant were measured in field cages in soybeans, Glycine max L., over 3 yr. Attack rates in the first 2 yr averaged 0.47 attacks per predator per day and were consistently low at low prey density. Area searched by predators was estimated from attack rates, and the estimated search area decreased as prey density increased. In a third field season, attack rates averaged 0.5 attacks per day at low prey density and increased linearly at high density. A negative exponential function was used to develop a model that described search area as a function of prey density. The model estimated that area searched ranged from a maximum of 0.50 m 2 at zero prey density to an asymptotic minimum of 0.055 m 2 at high prey densities. Searching less area as prey density increases keeps attack rates low and consistent at low prey density, and searching a constant amount of area at high prey density results in increasing attack rates at higher prey density. The search strategy may result from balancing energetic costs and predation risks with the benefits gained from attacking prey. Also, the strategy may reflect the budgeting of time between searching and other time-consuming activities (e.g., reproduction) by the predator. Determining the search strategy of predators may provide a better understanding of the requisites of generalist predators living in ephemeral crop systems.