In this paper, the writer summarizes the results of his investigations on the distribution of the pine leaf gall midge, Cecidomyia brachyntera SCHWAGE?, in Japan and particularly in the San'in distnct, and the damage of pines caused by it in Oki Islands, Shimane prefecture.
1) This species is found in various parts of Japan, as shown in Fig.1 and Table 1.
2) The species distributes itself over Shimane prefecture, as for the rest of the Sanin district, it is recorded at Yonago city and Sakaeminato city in Tottori prefecture and Hagi city in Yamaguchi prefecture (see Fig. 2).
3) Thearea damaged by this midge extend s widely over pine forests in Oki Island (see Table 2).