Field and laboratory populations of the parasitoid Asecodes hispinarum Bouek were randomly sampled, and sex ratios, the number of emerged and unemerged adults and egg numbers compared between the two populations.  t\|test indicated that these parameters differed significantly between the two populations. The proportion of females in the field population was 81.63%±2.54% compared to 65.34%±1.80% in the laboratory population and the number of emerged adults in the field population was 25.13±1.17 compared to 52.90±1.88 in the laboratory. The effect of host size on sex ratio was analyzed by correlation analysis; no relationship between host size and sex ratio was observed. This result is contrary to the prediction derived from Charnov’s model.