Fifth instars of the hemipteran predatorPerillus bioculatus(F.) were observed as they attacked neonateLeptinotarsa decemlineata(Say) larvae on potato plants. Observations were conducted at prey densities ranging from one to 100 prey per plant, and standard functional response models were fit to the predation rates obtained. Neither the type II nor the type III functional response curves provided a satisfactory fit to the data. The observed attack rate was neither constant over all prey densities (as in the type II model), nor an increasing function of prey density (as in the type III model). Instead, it declined over prey densities from one to 25 and then increased substantially at the density of 50. A possible explanation for the observed pattern is that area-restricted search following prey consumption led to additional successful feeding events at high densities but not at low densities. The mean observed handling time was essentially equal to an estimate based on the type III model and prey density did not have a Significant influence on per-prey handling times.