Abstract: Spalangia endius, a pupal parasite of flies, emerged from the pupae of four field collected fly species: Musca domestica, Muscina stabulans, Lucilia sericata, and L. illustris in Shanxi Province. There was only one wasp emerging from each parasitized pupa. The adults appeared during June to November, mostly in poultry and livestock farms, and increased in numbers during July to September. S. endius chose mainly 1-2 day-old pupae of M. domestica, M. stabulans and L. sericata to oviposite. The life cycle of the parasite was 18-20 days under 20-25℃, 80-90% RH and 16 hr. photophase. When the parasite was introduced to its host at a rate of 1 para.: 5 host in the caged experiment, the parasitization of M. domestica, M. stabulans, L. sericata and Chrysomyia megacephaia was 71%, 94.4%, 99.9% and 53.3%, respectively. Each female parasite could kill 10-30 fly pupae.