A predator’s functional response: Influence of prey species and size

Abstract

The relationship of predator and prey size on the functional response of Nephus includens feeding on either Planococcus citri or Planococcus ficus mealybugs was empirically investigated. We used small and large predators to examine the role of predator size; respectively second or fourth instar larva of N. includens. The prey were second instar nymphs or adult females of P. citri or P. ficus. All eight predator–prey combinations produced a type II functional response. For the larger predator, predator handling time increased as prey size increased while for the small predator it remained constant. It was hypothesized that this was due to a habit of the smaller predators to consume prey only partially. Maximum predation rate was always greater in combinations of large predator–small prey. Larval developmental stages of N. includens did not show a high density-dependence with different prey size, which might impede their potential as biological control agents. The study highlights the importance of size-structured populations of both predator and prey in functional response studies.