Abstract:The parasitoid Cotesia plutellae (Hymenoptera: Braconidae) -host Plutella xylostella (Lepidoptera: Plutellidae) system was used to evaluate the regulatory effects of wasp-associated factors, i.e. PDV, venom and teratocytes, on the growth and development of the host larvae by means of pseudoparasitism and superparasitism. The results showed that after pseudoparasitism the last-instar host larvae were distinctly prolonged in the developmental duration and eventually failed to pupate. At the beginning of pseudoparasitism host larvae increased in body weight more slowly than non-parasitized host larvae. However, at the final period of pseudoparasitism the pseudoparasitized host larvae could continue to feed and develop, and finally became extra-weight larvae (up to 10.52 mg/per larva) when the non-parasitized host larvae had already pupated. The development of normally parasitized host larvae was constantly checked as compared with that of the non-parasitized larvae. Super-pseudoparasitism could strengthen the inhibition of host development, probably due to more physiological doses of PDV and venom injected into the host larvae at wasp oviposition. It is indicated that there were many differences between the larval development and growth of the naturally parasitized and pseudoparasitized hosts, which were probably par- tially resulted from the functions of teratocytes.