Abstract: To understand the effects of host stage on the fitness of the offspring Aenasius bambawalei Hayat, the sex ratio and body size of their offsprings parasitizing Phenacoccus solenopsis Tinsley of different stages (3^rd instar nymph and adult)were determined under the laboratory conditions of (27±1) ℃, RH (70±5)% and 14L∶10D. Sex ratio, body length and hind tibia length of the offsprings of A. bambawalei parasitizing the P. solenopsis adult females were significantly higher compared to those parasitizing the 3^rd instar mealybugs. The hind tibia length of the offspring wasp was closely related to the body length. The body size of the parasitised 3^rd instar mealybugs affected the size of the offspring wasp of A. bambawalei significantly, while such relationship was not found between the adult female of mealybugs and the offspring wasp.