The life history was studied from June 1993 through April 1995 in a rainfed rice field of Bandar Bara District in Kedah, Peninsular Malaysia. Larval growth was more uniform during early instars. Increasing variations of growth were obvious during the later instars, especially in the final instar. Plots of head width against wing bud length and body length enabled instars to be determined. Larval development was asynchronous and a maximum of 8 larval instars was found on one sampling occasion. 4 emergences were observed in 1994, in March, May, July and October. In general emergence was relatively synchronized. The E50 values were achieved within the first 38%, 9% and 16% of the total duration of emergences 2, 3, and 4 respectively. A relatively short life cycle, continual breeding and oviposition, synchronous emergence and immediate reproduction after a dry period ensure survival of N. tullia in the unpredictable rainfed rice ecosystem.