Effect of prey and predator density on predation of rice leaffolder eggs by the cricket Metioche vittaticollis

Cage experiments were conducted to quantify the predation rate of the crick et Metioche vittaticollis (Stal) on the eggs of rice leaffolder Marasmia pa tnalis 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 fun ctional response could be adequately described with a linear Type I model, with the effect of leaf area included. This type of response to leaffolder egg density means that predation was not limited by prey handling time or s atiation, but by the search rate. The search rate is here interpreted as th e leaf area effectively searched for leaffolder eggs by a single predator i n one day. Estimated search rates averaged 0.13 m(2) day(-1) for M. vittati collis females. The search rate of the predators increased with prey densit y, but a model describing a density dependent search rate explained only 3% of the total variation in search rate. Increasing predator density per cag e led to a decrease in the per capita egg predation rate when predator dens ity was more than two per m(2) leaf area. Interference might thus reduce th e potential to enhance leaffolder egg predation by conservation or augmenta tion of predatory cricket populations.