“Rhyzobius ventralis” is a well-known coccinellid as a scale insect control agent in various parts of the world since 1890s. But, it had been confused with R. forestieri until Pope (1981), who separated these two species and reviewed the previous records. As the first record from Japan, R. forestieri was collected on leaves of Elaeocarpus sylvestris with heavy infestation of the mango shield scale Protopulvinaria mangiferae in Fukuoka City in April, 1987. The present study was carried out on this coccinellid to get some biological parameters by rearing with the mango shield scale as food. Results obtained are summarized as follows: 1. The total number of eggs laid by a female is 439 in average. The eggs are laid singly, but by repeated ovipositions 5.1 eggs in average are laid on the ventral side of an adult scale, or 1.5 eggs in average in an empty mummy of the scale in Petri dish. 2. The threshold temperature (t_0) and the thermal constant (K) for the development from the egg to the adult eclosion are calculated 11.3℃ and 338 day-degrees, respectively. 3. Under 25℃ and 16hrs light conditions, the premating and preoviposition periods are 3-4days and 6-7days, and the durations of the egg, larva and pupa are about 6, 13 and 5 days, respectively. 4. Under the same conditions, the longevity of the adult is about 95 days in both sexes, and the net reproduction rate (R_0) and the intrinsic rate of natural increase (r_m) are calculated as 192.3 and 0.085 per female per day, respectively.