EFFECTS OF SIZE AND FLUCTUATING ASYMMETRY ON FIELD FITNESS OF THE PARASITOID TRICHOGRAMMA-CARVERAE (HYMENOPTERA, TRICHOGRAMMATIDAE)

1. The effects of body size and asymmetry in morphological traits on f ield fitness were studied in the parasitoid Trichogramma carverae. 2. Significant fluctuating asymmetry was detected in four bristle counts and two wing measurements made on forewings. There was no evidence for directional asymmetry in any of the traits. An estimate of field fitn ess was obtained in grapevines by collecting released wasps arriving a t oviposition sites consisting of egg rafts of the tortricid Epiphyas postvittana. 3. Comparisons of ovipositing and emergence samples indic ated that wasps at oviposition sites were relatively larger and more v ariable in their size distribution. A non-parametric analysis of the r elationship between fitness and size indicated that extremely large wa sps had the highest fitness and suggested that small as well as large wasps may have had a fitness advantage. 4. For asymmetry, the only tra it showing an association with field fitness was wing length. Wasps wi th a low length asymmetry were more likely to be collected at oviposit ion sites, although fitness curves indicated that wasps had a similar fitness once an intermediate length asymmetry was exceeded. 5. Mother- daughter comparisons for wasps from a genetically heterogeneous stock provided no evidence that size measures or asymmetries were heritable when wasps were reared on a factitious host. 6. These findings have im plications for improving parasitism rates in inundative releases.