Abstract: Tetrastichus nigricoxae Yang is an endoparasite of pupae of Micromelalopha troglodyta Graeser. It is the mian pest of Poplar in China. In this paper the morphology, behavior, development, survival and reproduction of the parasitoid were studied. The results showed that the ehalcid could swarm from hosts, oviposite and mate after emerging1--2 days, and the behavior of mating and oviposition could last 0.5--2 min, and 1--3 min, respectively. The average number of parasitoid emerged from each host was (70.2 +34.2), and the female rate was (6.1 ±5. 1) : 1. The developmental duration of 1 generation was 37.0 days under the laboratory condition of (20± 2)℃ ,RH (75 ± 10)% , and L:D=12:12, but was only 19.5 days under (28±2)℃, RH (75 ±10)%, and L:D=12:12. Sweet resources such as honey, sucrose, and glucose, especially honey, could prolong the longevity of adults and increase the fecundity and parasitism of females effectively.