Field life-tables and key mortality factors of castor semilooperAchaea janata L. were studied on castor for the year 1985–86 and 1986–87. There were 4 regular overlapping generations during both the years. The parasitization ofAchaea janata larvae in early instars (I–III instar) by parasiteMicroplitis maculipennis (Sziepligetis) was 1·34, 4·41, 22·02 and 43·70% in first, second, third and fourth generation respectively during 1985–86. Similarly, the parasitization by same parasite was 44·12, 61·46 and 65·55% during second, third and fourth generation respectively in the year 1986–87. Key mortality factors and separate budget for each generations were prepared.