The ovipositor of parasitic insect is a highly specialized organ and crucial for parasitising. Morphology and structure of the ovipositor in female Macrocentrus cingulum, a polyembryonic parasitoid, are observed in SEM studies. The ovipositor of M. cingulum consists of the valvulae 1, 2 and 3. The valvulae 1 and 2 of ovipositor house in the valvulae 3 at rest and the valvulae 1 and 2 part from the valvulae 3 at probing and ovipositing. The cross-section of valvulae 3 shows that the valvulae 3 is hollow which may reduce the weight of ovipositor and make the ovipositor more flexible. The distal end of stylus （valvulae l, 2） becomes extremely sharp and the piercing tip of valvulae 1 and 2 form the arrangement of tongue-and-groove. This arrangement may support valvulae 2 slide longitudinally along the valvulae 1. Numbers of pores are distributed on the cuticle of the valvulae l and 2. The piecing tip of valvulae 1 and 2 have more pores than proximal and intermediate region. The out side of valvulae 3 is completely covered with chactica sensilla and the distal end of valvulae 3 has more sensilla than proximal and intermediate region. The function and structure of ovipositor of M. cingulum was discussed and compared with other species.
