Abstract
The larvae of the rice leaf roller, Cnaphalocrocis medinalis (Guenèe), fed rice leaves from the vegetative growth period until panicle formation developed to the 5th instar and pupated regardless of the variety and position of leaves given to them. In larvae fed leaves after the booting period, 6th or sometimes 7th instar larvae appeared. The frequency of these extra-molting-type larvae increased as the rice growth stage advanced. In addition, the growth speed of the larvae was reduced even within the same instar. Larvae fed leaves at the ripening stage showed a decrease in pupal weight. These influences on larval development also varied according to the position of the leaves given. Marked negative effects were observed in larvae fed flag leaves as compared to those fed lower leaves. Particularly, many 1st instar larvae fed flag leaves during the ripening period died. Thus, the position of leaves consumed appears to affect larval survivorship. These changes in larval development and survival rate seem to be caused synergistically by differences in the nutritional value and hardness of leaves of the food plant.
