Studies on the color variation in larvae ofEphestia kühniella Zeller (Lepidoptera: Phycitidae) III. Fitness of different larval color strains

The population fitness in terms of the intrinsic rate of increase r_m was measured in eight pure (homogenic) strains of Ephestia kühniellaZeller with different larva color at an optimal temperature of 25°C, and in three strains at unfavorble temperatures of 15, 17, 28, and 30°C, to understand a mechanism of maintenance of a larval color variation found in wild populations. The survival rate, hatchability, and gross rate of reproduction were poorly correlated with the fitness but the mean generation time and net reproduction rate were correlated with the fitness significantly at 25°C. Intermediate color (pink) strain(s) grew faster, initiated reproduction earlier and had shorter longevities than other strain(s) under the range of 15 and 28°C; the fitness was highest in the intermediate larval color strains except at 30°C in which all strains had a negative rate of increase. The results were discussed with reference to the relationship between the larval color and fitness along with a maintenance mechanism of the variation.