NATURAL ENEMIES OF THE RICE CASEWORM NYMPHULA-DEPUNCTALIS (GUENEE) (LEPIDOPTERA, PYRALIDAE)

Larval and adult predators comprise the largest component of the natur al enemy fauna which attack the semi-aquatic rice caseworm Nymphula de punctalis (Guenee). Spiders, birds, and adult dragonflies/damselflies were the dominant predators of caseworm adults, while aquatic beetle l arvae, aquatic bug nymphs and adults, and ants preyed on caseworm larv ae. Egg parasitoids are unknown in nature and larval/pupal parasitoids are rare. A nuclear polyhedrosis virus, the only recorded pathogen, o ccurs but rarely. A ricefield pulmonate snail Lymnaea quadrasi (Mollen dorff), which forages on algae, causes limited caseworm egg mortality in a passive and fortuitous manner. Water beetles-the dytiscid Cybiste r tripunctatus orientalis Gschwendtner and hydrophilid Sternolophus ru fipes Fabricius-are voracious larval predators. Prey consumption by th ese water beetles is higher on older caseworm larvae whose larger size creates more movement while the larvae are crossing the water surface . Also, older caseworms are more prone to leave the protection of thei r cases while under attack. Younger caseworm larvae, however, tend to retract and remain motionless when attacked. The last instar dytiscid preyed on an average of 11.4 caseworm larvae per day while that of the hydrophilid preyed on 6.7 larvae per day.