In order to understand oviposition strategy of the uniparental endoparasitoid Meteorus pulchricornis on host larvae of the beet armyworm Spodoptera exigua, non-choice and paired choice experiments were conducted in the laboratory. Parasitism on different instar larvae and development performance of the parasitoid offspring were observed. In the non-choice experiment, though all five instars of host larvae were susceptible to parasitization, the parasitism differed in that the 2 -4 instars were significantly parasitized ( > 70% ) than the first instar (53%) and the fifth instar (20%) . The development performance of offspring parasitoids was also different among host instars where parastization commenced. Parasitoid larvae pupated ( > 95% ) after egression and a-dubs eclosed ( >90% ) , derived from eggs oviposited in 2 [long dash] 4 instar hosts, more than those from eggs oviposited in the first and the fifth instar hosts. Larval development time of the parasitoid, measured from oviposition to adult eclosion, was shorter for the 2 -4 instar hosts than the first and the fifth instar hosts where eggs were deposited. Body sizes of offspring parasitoids, represented by hind tibia length, increased with host instars where the parasitization commenced. Combined fitness returns for the parasitoid showed that the second through the fourth instar hosts were more suitable for its development. In the paired-choice experiment, M. pulchricornis preferred older hosts to the young but the inverse occurred when the fifth instar host was offered, which was consistent with the conclusion from the non-choice experiment. none