Abstract: Through observations on the rate of ovarian development, quantitative analysis of soluble protein and nucleic acid, rocket immunoelectrophetic measurment of vitellogenin titer in hae-molymph and hormone treatments, the inhibitory effec, of precocene II on vitellogenesis in tile housefly Musca domestica vicina was investigated. When the newly-emerged femalehouse-flies were topically treated with precocene II in 20 ug/fly, vitellogenesis was temporally inhibi, ed and the development was delayed 12 hours than that of the control. At 48 hours aftertreatment, the titer of vitellogenin in haemolymph was 10.5ug/ul, nearly the same as the control, but the development of ovary was retarded as compared with the contro. This temporalinhibitory effect seemed to indicate tbat the uptake of vitellogenin by oocyte was partially in hibited. When the treatment was in high doage abom 100 ug per fly, the titer of vitellogeninin hemolymph and the weight of overies, ,oral protein and RNA in ovaries were obviously lower when compared with the control, indicating that the development of the ovary and the synthesis of vitellogenin wer inhibited It was observed that the inhibition could be restored naturally. When the treatment of precocene II was followed with application of JH Ill, the inhibition of vitellogenesis was not conspicuous and the titer of vitellogenin in haemolymph was two times that in temporally inhibited flies. When precocene II treatment was followed with to pical application of 20-hydroxyecdysone, the vitellogenesis was still inhibited. The mode of action of precocene on ovarian development of dipteran insect is discussed.

Key words: Musca domestica vicina — precocene II — vitellogenesis — vitellin