Effect of larval density on development and diapause of Sesamia nonagrioides (Lef.) (Lep., Noctuidae) under laboratory conditions

The effect of larval density on development and diapause of Sesamia nonagri oides (Lef.) was examined. Larvae were grown on an artificial diet at densi ties of five, 10, 20, 30 and 40 larvae per box, under two environmental (di apause-including and diapause-averring) conditions. High larval densities r esulted in increased mortality under both experimental conditions tested. A lthough crowded larvae showed a higher pupation rate than those reared unde r low densities, small differences occurred between mean larval development al time at different densities under developmental condition. In spite of t his, crowding proved effective on the intensity of diapause of this species and the duration of diapause was shorter for crowded larvae. Pupal weights of both sexes were significantly reduced at high densities while there wer e significant differences between pupal weights formed by larvae reared und er diapause conditions and those formed by larvae reared under nondiapause conditions at all density treatments. The pupal period was significantly lo nger under diapause conditions than that under development conditions but d ensity was not found to play a role on the time of the emergence of the adu lts produced by larvae reared under developmental or diapause conditions.