Abstract: Foxtail millet webworm (Manpava bipunctella Ragonot) is an insect with facultative diapause, it has two generations per year in southern Sichuan. Photoperiod is the main factor in inducing diapause. The percentage of its population entering diapause is decided by photoperiod in early larval stage at medium temperature. The critical phoroperiod is 14 hours and 38 minutes at 25℃ constant temperature, the first and second larval instars being the sensitive stage.The influence of temperature and food on diapause depends largely on long light period.Low temperatures would inhibit the diapausing effect of long light period. High temperatures,however, had no significant effect. More larvae entered diapause feeding on corn than on sorgh,lm. Light period between 14 and 15 hot, rs was the main factor for diapausing larvae ,orevive. The influence of diapause on the population dynamics of tile pest and the significance in pest forecast are discussed.

Key words: foxtail millet webworm——diapause——photopeilod ——temperature ——hostplant