Abstract
Effects of temperature on development of the rice leaf roller, Cnaphalocrocis medinalis, were investigated both in the laboratory and in the field. When the insect was reared under constant temperatures, velocity of development showed a linear relationship with temperature in a certain range. The threshold temperatures of development in egg, larva and pupa were estimated to be 12.5, 12.2 and 14.2°C, and the thermal constants 57.1, 203.7 and 81.2 day-degrees, respectively. Remarkable elongation of larval development occurred when larvae were reared on rice leaves at the ripening stage. The larval durations of the respective generation in 1978 were estimated from surveys of population occurrence in early and normal planted paddy fields and the heat accumulations in the larval periods were calculated. They were 210-240 day-degrees in the generations before mid-August and about 300 day-degrees after late August. One of the reasons for this difference seemed to be that the rice plants became less favorable as food for the larvae after late August. Adults lived about two weeks at 25°C when a 10% sucrose solution was offered.
