Seasonal changes in female size and its relation to reproduction in the parasitoid Asobara tabida

The relation between female size and fitness was studied in female Asobara tabida throughout the held season. The size of A. tabida females Varied con siderably, with average size being smallest in the middle of the season. Th ere was a positive correlation of realized fecundity with size, and the fit ness advantage of larger females increased later in the season. A possible explanation for this can be found in the energy expenditure during the seas on. Regression analysis showed that fat use increases with size of the fema le, but also with temperature. Temperature was low early and late in the se ason, but high in the middle. We argue that the high temperatures may const rain fitness advantages of large females because of their increased metabol ic needs. Variation in the form of the fitness function within the season m ay moderate directional selection for larger females.