none Development, mortality, and adult longevity of Microplitis rufiventris Kokujev, an imported parasitoid of the beet armyworm (BAW), Spodoptera exigua (Hubner), was studied in relation to constant temperatures in the laboratory. This study provided estimates of both lower (10.3 degree C) and upper (29.5 degree C) thresholds for development. M. rufiventris successfully attacked and parasitized second-instar BAW larvae, and regardless of rearing temperature usually emerged from fourth-instar larvae. Immature mortality ranged from 0.0 to 21% between 17.5 and 32 degree C; at 33.5 degree C all individuals died before reaching the adult stage. Adult longevity declined as a function of temperature, ranging from ca. 25 days at 17.5 degree C to 4 days at 32 degree C. Results of this study indicate that there is sufficient abiotic potential for M. rufiventris establishment in Arizonia (USA).