Abstract: Prophenoloxidase-activating system (proPO-AS ) is one of the most important humoral immunity systems in insects. The crude extracts of Trichogramma ostriniae, T. chilonis and T. dendrolimi were collected by grinding and centrifugation, and PO activities of three Trichogramm species induced by calcium ions, laminarin, dextran, and PMSF were compared. The results indicated that the highest PO activity was found in the crude extract from T. ostriniae, followed by T. chilonis, and then T. dendrolimi. Ca²⁺ was required for PO activation, and the maximal activation was observed at the Ca²⁺ concentration of 0.03 mol/L. Laminarin and lipopoyusaccharide could also effectively activate proPO, and 0.01 and 0.05 mg/mL laminarin caused strong activation. Cellulose and dextran were proved to be significant inhibitors to PO. A model for proPO-AS studies of small insects was established, which provides an experimental basis for studying the interaction of immune system of symbiotic bacteria-small insects.

Key words: Trichogramma dendrolimi, Trichogramma chilonis, Trichogramma ostriniae, prophenoloxidaseactivating system (proPO-AS), prophenoloxidase, enzyme activity