Of recent years the population density of the rice green leafhopper in paddy-fields has increased. One of the reasons of this increase is said to be the result of the decrease of the natural enemies of this hopper owing to the wide application of insecticide in the paddy-fields. And so the more informations concerning in the natural enemies of this hopper are needed. Up to now, following natural enemies of this hopper has been listed from Japan. Among these, Nos. 3, 8, 10, 14 and 17 are said to be most useful for the check of this hopper. On the parasitic Dorilaidae, there has been no further informations since the valuable paper of Esaki and Hashimoto (1937). Thus the members of this family have long been throughly neglected. But these flies no doubt play a very important part in helping to keep this pest in check, juding from the high percentage of parasitism found in the data of the hoppers disected and the abundance of hovering adult flies in the paddy-fields. In this paper, four species of the Dorilaid fly reared from the green rice leafhopper are described, of which three are new to the science and one is new to the fauna of Japan- Ecological items and about immature stages of these flies will be given in the forthcoming Series of paper. Before going further, I wish to express my sincer gratitude to the entomologists mentioned below for the loan of materials ; Dr. S. Ito of the College of Agriculture, University of Osaka Prefecture, Messrs. H.Hasegawa and N. Fukuhara of the National Institute of Agric. Sciences, Tokyo and Mr. A.Tsuboi of the Okayama Agric. Exp. Station.