Some biological phenomena of Anagrus incarnatus Haliday, an egg parasitoid of planthopper, were studied under three different constant temperatures. Duration from egg to adult emergence of the parasitoid from the BPH eggs were 21.5, 13.6 and 10.6 days under $20^{circ}C$, $25^{circ}C$ and $30^{circ}C$, respectively. Rate of the development was highly correlated with temperature. The critical temperature was estimated as $10.0^{circ}C$ and the effective degree days was 210.3 day-degree. Durations for the development of A. incarnatus under 25$pm$$1^{circ}C$ (16L : 8D) were 12.4, 12.5 and 12.1 days from eggs of N. lugens, S. furcifera and L. striatellus, respectively. Duration of the development of A. incarnatus from 1, 3, 5, 7 days old BPH eggs were 12.5, 12.1, 12.9 days, respectively. The average longevity of adult was 5.3 days under 25$pm$$1^{circ}C$. Number of the ovarian and practically oviposited eggs were 34.8$pm$28 and 28.3$pm$0., respectively. Female A. incarnatus laid most of the eggs within few days after the emergence ; over 60% within 24 hours, nearly 90% upto the 2nd day, and nearly 100% upto the 3rd day.