Tetrastichus planipennisi (Hymenoptera: Eulophidae) is a gregarious larval endoparasitoid from China that is being released in the United States as a biocontrol agent of the emerald ash borer ( Agrilus planipennis Fairmaire), an exotic beetle responsible for widespread ash mortality. The developmental time of immature stages, adult longevity, reproductive age, oviposition rate, and realized fecundity were determined in the laboratory under normal rearing conditions (25 ± 2 °C, 65 ± 10% RH, and L:D 16:8 hr photoperiod). It takes approximately four weeks to complete a single generation (from egg to adult) under normal rearing conditions. While male wasps lived for a median of 5 weeks, females lived significantly longer with a median survival time of 6 weeks and a maximum survival time of 9 weeks. Newly emerged females appeared to be as capable of producing progeny as older females, indicating that T. planipennisi may be synovigenic. The average number of progeny per reproductive female remained relatively constant through the first 6 weeks of the trial with each reproductively active female producing 23-26 progeny each week. Lifetime realized fecundity of the adults averaged 57 progeny per reproductively active female with a female-to-male sex ratio of approximately 3:1; the maximum number of progeny produced by a single female was 108. These results suggest that T. planipennisi may have several generations in the mid-Atlantic and Midwestern regions of United States, where normal growing seasons (with average temperature 25 °C) are normally four to five months (May-Sep). Because of the gregarious nature, long life span and oviposition period of adults, T. planipennisi is likely to have multiple overlapping generations and has the potential to be an effective biocontrol agent against EAB.