Abstract: The mating system of Caenorhabditis elegans includes selfing hermaphrodites and the males that cross with hermaphrodites. In labcultured C. elegans populations, the proportion of the males is very low, and till now, no detectable fitness of crossed offspring has been found. To explain why the C. elegans conserves a complicated pathway of male development through evolution, we compared the life history of the males and hermaphrodites under heat stress as well as the resistance of the populations with and without males against the heat stress. The results showed that though the life span of the males was more affected by heat stress, as compared with that of the hermaphrodites, the C. elegans populations with the males recovered faster after the stress, and the populations continuously subjected to the heat stress could maintain a higher proportion of the males than the populations cultured at normal temperature. These findings implied that under changeable natural environment, the existence of male C. elegans could be a significant evolutionary strategy for the population survival.