Abstract: The biology of Propylea fallax (Khuzorian) was studied in the laboratory using mungbean aphid as food. Mating period generally lasted upto 2 hours. A female laid 507.2 eggs on an average. The mean incubation period of the egg was 2.1 days with hatchability 98.87 percent. The larva completed four instars in 5.3±0.19 days with almost similar duration of 1.5, 1.15, 1.05 and 1.6 days for 1st, 2nd, 3rd and 4th instar, respectively. The pre-pupal and pupal periods were 1.2±0.13 and 2.0±0 days. Adult longevity of male was 15.6±0.57 days and 19.6±0.66 days for the female. The average aphid consumption of the larva was 168.5±7.18 and adult 806.6±73.65. Both adult and larva preferred aphids having body width 0.25-0.75 mm, whereas above 1.0 mm were least preferred.