Abstract
1. Present authers investigated the external charactors and geographical distribution of D. ianthes, which is a micro-lepidopterous insect belonging to the family Gelechiid and an important pest of Ladino clover in Japan. 2. D. ianthes is widely distributed throughout such areas of Asia and Africa as Japan, Formosa, Malaya, Java, Celebes, India, Ceylon, Reunion, Mouritious, Seychelles, Egypt, East-Africa etc. In Japan, it is distributed in Kyushu, Shikoku and most part of Honshu but not distributed in the northern part of Honshu and Hokkaido. D. ianthes is considered to be a southern species. 3. The northern limit of the distribution of D. ianthes exists in Honshu of Japan as shown in Fig. 6. The limiting line is supposed to run from the Pacific coast of the northern Miyagi prefecture to the Japan Sea coast of the south-western part of Niigata prefecture through Fukushima prefecture and the northern Nagano prefecture. 4. The limiting line is generally coincided with the isothermal line of 11℃ or the 50cm line of maximum snow depth. It may be concluded therefore that the distribution of D. ianthes in the northern limiting zone is much influenced by the low temperature and snow in winter.
