In the bruchid Caryedon serratus, life span of males was longer than that of females. Catalase showed an increasing trend with age in both the sexes but the increase was higher in males. However, an opposite trend was observed for lipid peroxide levels. A rapid decline of NADH and succinate dehydrogenases in females is indicative of early depletion of food reserves due to the higher metabolic rate. Thus, in C. serratus, the factors contributing to relatively higher life span of males are efficient homeostatic defence mechanisms and low oxidative damage in males, early maturity and more reproductive demands in females.