Abstract: Strepsiptera are very specialized insects which carry out a unique type of viviparity with egg formation and embryonic development taking place within haemocoel of the female. Elenchinus japonicus belongs to Elenchidae, Strepsiptera, and parasitizes the planthoppers Sogatella furcifera, Nilaparvata lugens and Laodelphax striatellus. In this work the stages of egg formation and embryonic development in S.Furcifera were carefully observed microscopically. The female insect lacks typicalovaries; the eggs develop and mature synchronically within the adipose tissue near the body wall. At the beginning, the primary oocytes are derived from the cystoblasts each of which consists of 256 sibling cells. One of these cells differentiates into the oocyte and the rest become the nurse cells. The mature egg is ellipticaland measures 75-100×40-50μm. It undergoes cleavage, blastoderm formation,segmentation of germ band, formation of appendages and dorsal enclosure to form the mature embryo monoembryonically.

Key words: Strepsiptera——Elenchinus japonicus——egg formation——embr- yonic development