In several species of wasps belonging to the genusPolistes, the first workers to emerge during the colonial cycle are smaller than the foundresses. As the cycle proceeds, the emerging workers are larger and larger, so that when the future reproductives appear they are no larger than workers of the same age. This study analyzes the size differences found in the workers and foundresses in a sample of 638 females collected in the course of one year. After anatomical analysis, each female was assigned to one of the following groups: foundress, future foundress and worker. Each individual was measured for maximum head width and right wing length. Although the size of emerging females also increases inP. gallicusas the season advances, workers are always smaller than the foundresses, and the future reproductives always larger than workers found on the nest at the same time. Results also suggest that the smaller future foundresses are selected out during overwintering.