DIAPAUSE TERMINATION IN SESAMIA NONAGRIOIDES (LEPIDOPTERA, NOCTUIDAE)UNDER LABORATORY AND FIELD CONDITIONS

The influence of photoperiod and temperature on the termination of dia pause of Sesamia nonagrioides (Levebvre) was evaluated under laborator y and field conditions. Long-da,: photoperiod enhanced termination of diapause. Larvae held under a short-day photoperiod (10:14 [L:D] h) fo r various times and then transferred to a long-day photoperiod (16:8 [ L:D] h) proceeded to pupate in approximate to 14 d, indicating that re gardless of the state of diapause intensity, diapause completion and p ostdiapause development listed similar lengths of time. Larval diapaus e termination was not hastened when diapausing larvae kept at a photop eriod of 10:14 (L:D) h and 25 degrees C were exposed for short periods at 30, 35, and 40 degrees C. whereas it was shortened when diapausing larvae were transferred from 25 to 30 degrees C and kept continuously at this temperature. At higher temperatures (35 and 40 degrees C), al l transferred larvae died. It was also shown that exposure of diapausi ng larvae to low temperature (5 degrees C) simply accelerated diapause development but termination of diapause did not require a period of c hilling. Moreover, after low temperature treatment. diapausing larvae showed a faster diapause development when transferred to a long-day ph otoperiod than those kept in a short-day photoperiod. In thr latter ca se, the longer the exposure the faster the termination occurred. Diapa use termination of field-collected larvae was practically spontaneous. After transfer to laboratory conditions, 25 degrees C and a photoperi od of 16:8 (L:D) h. they quickly proceeded to pupate. Field-diapausing larvae terminated diapause in January but exhibited. a postdiapause d evelopment; the Ist record of pupation was observed in the field at th e end of March.