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 (3rd instar nymph and adult) were determined under the laboratory conditions of (27 +/- 1) degree C, 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 3rd instar mealybugs. The hind tibia length of the offspring wasp was closely related to the body length. The body size of the parasitised 3rd 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.