The effects of within-plant variation in seed size ofRosa multifloraThunb. on adult size, emergence, and morphology of the seed-feeding torymid waspMegastigmus aculeatus nigroflavusHoffmeyer were investigated. Large seeds were proportionally the most heavily infested by the wasps, and seed size significantly affected body size of emerged adults. Success in emerging from the seed was not influenced by seed size. The static intraspecific allometry of wasps was determined. Three of nine measured characters (length of scape, length of pedicel, ocellocular distance) had a negative allometric relationship (i.e., slopes of<1.0) when log-transformed and plotted against thorax length; the remaining measurements were isometric.