Abstract:Beijinga utila Yang is an ectoparasite and monoparasitism insect. It is an important natural enemy against Eulecanium gigantea (Shiji) and Eulecanium kuwanai (Kanda 1934). It has one generation each year. The pupa cocoons overwinters under the scales of female host adults. Its imagos emerge till the first or the second ten-day of May, which are corresponding with imago stage of the female host insects. So the scale insects can be effectively suppressed. The average parasitiztion is 32.7% (from 22.5% to 44.2%) on Eulecanium gigatea (Sliji) during 4 years, and 15.1% (from 7.4% to 21.5%) on Eulecanium kuwanai (Kanda 1934) during 3 years. It choices the host. Parthenogenesis is not occurred in this species, and the larvae usually kills each other.The larvae of Beijinga utila Yang is obviously not affected by the poisons when chmicals is used to control the new-hatched nymphae, the last 1st-instar and early 2nd-instar nymphae of the scale insects. Temperature has a greater effects than relative humidity on ernergnce, coition and ortposition. But its incubation dos not demand the strict temperature and relative humidity.