none The times required for virgin Bracon hebetor Say females to mate with males of different degrees of relatedness were recorded. The data were analyzed as a waiting-time model usig the statistical program GLIM. Two strains were tested; females of one mated more rapidly than those of the other. Matings between females and sons were significantly faster than between females and brothers or unrelated males. The mating times of females with brothers is not significantly different from that between females and unrelated males. The biological significance of several hypotheses are discussed. These data are consistent with the hypothesis that accelerated mating of mothers with sons is an adaptation for the invasion of new habitats by virgin B. hebetor females.