Effect of Prey and Predator Density on Predation of Rice Leaffolder Eggs by the Cricket Metioche vittaticollis

Abstract

Cage experiments were conducted to quantify the predation rate of the cricket Metioche vittaticollis (Sta Ê l) on the eggs of rice leaVolder Marasmia patnalis Bradley. Egg predation by adult females was measured in response to changes in egg density, predator density and leaf area per cage. The number of eggs consumed per predator increased with egg density, without reaching a plateau. The predation rate decreased with increasing leaf area. The functional response could be adequately described with a linear Type I model, with the eVect of leaf area included. This type of response to leaVolder egg density means that predation was not limited by prey handlin g time or satiation, but by the search rate. The search rate is here interpreted as the leaf area eVectively searched for leaVolder eggs by a single predator in one day. Estimated search rates averaged 0.13 m 2 day 2 1 for M. vittaticolli s females. The search rate of the predators increased with prey density, but a model describing a density dependent search rate explained only 3% of the total variation in search rate. Increasing predator density per cage led to a decrease in the per capita egg predation rate when predator density was more than two per m 2 leaf area. Interference might thus reduce the potential to enhance leaVolder egg predation by conservation or augmentation of predatory cricket populations .