Identity and relative importance of egg predators of rice leaffolders (Lepidoptera : Pyralidae)

Field and laboratory studies on predation of rice leaffolder eggs (i.e., Cn aphalocrocis medinalis (Guenee) and Marasmia patnalis Bradley) were conduct ed to identify major predator species. Direct observations of predation on field-exposed eggs showed that in two seasons Metioche vittaticollis (Stal) and Anaxipha longipennis (Serville) were the major predators of leaffolder eggs, Together these crickets took the largest part of all eggs consumed d uring observation (92%) and had the highest ratio of visits with predation to their total observed visits to plants with leaffolder eggs. Furthermore, the activity pattern of the crickets matched best the daily pattern of egg disappearance, and the seasonal trends in their observed visits correlated best with the seasonal trends in egg disappearance. Minor predators feedin g on field-exposed rice leaffolder eggs were Ophionea nigrofasciata Schmidt -Goebel, Micraspis sp., and Conocephalus longipennis (de Haan). The latter species was the most commonly observed egg predator, but had a negligible s hare in the total predation. In petri dish tests the consumption of leaffol der eggs by the predatory crickets M. vittaticollis and A. longipennis was far greater than that of four other predators. Female cricket adults consum ed at least 80 eggs per day, and all individuals accepted leaffolder eggs a s food. According to daily egg consumption and acceptance rates, the predat ors ranked as follows: M. vittaticollis, A. longipennis > Micraspis sp. > O . nigrofasciata > Paederus fuscipes Curtis, C. longipennis. Predator rankin g according to the ratio of visits with predation to total visits in the fi eld was identical to the ranking based on the egg consumption tests. Due to their large predation potential, predatory crickets will probably play an important role in leaffolder egg predation, even when their densities are l ow compared to those of other predator species. (C) 2000 Academic Press.