The purpose of this paper is to describe the results of investigations on the parasitism of Gonatocerus sp.(Hymenoptera : Mymaridae), an egg parasite of the green rice leafhopper, Nephotettix cincticeps Uhler in the paddy fields in Kisugi and Matsue in 1974.
1. Gonatocerus sp. is active from the early of July to the early of October in the paddy field.
2. Average parasitisms of the egg masses by Gonatocerus sp. in rice growing season were 48.73% at A field, 57.81% at B field in Matsue and 66.67% at C field, 60.71% at D field in Kisugi while those of the eggs were 35.44% at A field, 39.35% at B field in Matsue and 55.92% at C field, 51.59% at D field in Kisugi.
3. Gonatocerus sp. was an important parasite of Nephotettix cincticeps Uhler on rice plant.