An endoparasitoid wasp, Cotesia plutellae, has been used for a biological control agent against the diamondback moth, Plutella xylostella. It has a symbiotic polydnavirus in their reproductive tract, which is required for its successful parasitization. Here, we measured a specific replication time of the polydnavirus during female development of C. plutellae. We, also, analyzed the reproductive potentials of female C. plutellae under mating or different host conditions. At 25[degree]C, pupal C. plutellae began to develop adult tissues such as compound eyes and wings since day 2. At day 5, all adult tissues including antennae were developed and were ready to emerge. With polyclonal antibody raised against C. plutellae polydnavirus, an immunobloting could confirm virus replication at day 4 during pupal stage. Virus particles could be visualized by transmission electron microscope in the oviduct lumen of day 5 pupae. After adult eclosion, venom gland and ovarian calyx increased in size, though ovarioles did not. Mated females layed large number of eggs (over 60%) at first 4 days during their mean longevity of ca. 8 days at 25[degree]C. Unmated females showed less active ovipositional behavior, where all the eggs developed into males. C. plutellae parasitized both P. xylostella and fall webworm, Hyphantria cunea. However, C. plutellae developed faster and showed higher successful parasitization in P. xylostella than in H. cunea. Reproduction; Reproductive behaviour; Life cycle and development; Development; Associations Cotesia plutellae (Braconidae); Egg laying; Ovipositional habit; Pupal development; Associations; Polydnavirus; Viral replication dynamics none