An aphidophagous coccinellid, Harmonia axyridis PALLAS, were reared in the insectarium without any environmental control for a period from May 18 to June 2, 1968. Average durations of the 1st 2nd, 3rd and 4th larval instars were 88.90, 61.35, 80.65 and 129.22 hrs, respectively. Average numbers of aphids eaten in those instars were 4.95, 9.60, 27.15 and 100.22 though beetle did not take any aphid during the time of ecdysis, 25, 15, 23 and 4hrs. The relation between the log number of aphids eaten(y) and larval instars(X) was expressed by an equation : Y=0.2893+0.0048 X. Average number of aphids eaten per day by an adult was 17.17. The beetles were active in predation for the period from 10 to 16 O'clock of a day. This indicates that the beetle may be active throughout the daytime, thought it is largely affected by temperature, humidity and evaporation in environment.