While studying the moths which were collected by light traps in the paddy fields at several agricultural experiment stations in Japan and identified as Chilo suppressalis , we happened to find several specimens of Chilo hyrax Bleszynski which was described in 1965 on the specimens from Ussuri and China and has been unrecorded from Japan. Up to the present about 5000 specimens of the so-called Chilo suppressalis have been gathered from 53 localities in 22 prefectures for taxonomic re-examination. Among them we have examined 645 specimens from 3G localities and could find 36 male specimens of Chilo hyrax from 8 localities in Akita, Niigata, Fukui, Kagawa and Fukuoka Prefectures. Male of this species may be distinguished from those of suppressalis by the following characters. Frons with a distinct projecting edge just before the ventral margin. Forewing much darker than suppressalis; greyish brown patches on discocellulars and just below discoidal cell absent, rarely visible. Length of forewing slightly longer than suppressalis: 10.1-14.1 mm. Male genitalia sclerotized more heavily than suppressalis; juxta slender with a small tooth near apex, without enlargement; cephalic end of vinculum somewhat enlarged in lateral view. The characters to distinguish the females of both species given by Bleszynski are quite unreliable because of their wide variation. Therefore, it is our urgent need to establish the female characters to distinguish the species. The present specimens were found from the materials of both first and second emergence of moth of "C. suppressalis." Therefore, this species is thought to have at least two generations a year. The earlier stages and host plants of this species are unknown. However, it is supposed that this species may attack the rice plant, and the larva may be closely allied to that of suppressalis judging by the present morphological knowledge of this genus. Japanese species of the genus Chilo may be separable by the following key. /Key to the Japanese species of Chilo (Male genitalia) 1.Juxta symmetrical……2 —Juxta a symmetrical…...C. phragmitellus (Hübner) 2.Aedeagus distinctly bifurcate at one third from base......3 —Aedeagus not bifurcate, or with a short process in some species......4. 3.Juxta with prominent enlargement......C. suppressalis (Walker) ―Juxta slender, without enlargement......C. hyrax Bleszynski 4.Aedeagus with a short process near base or at one third from base......5 —Aedeagus without a process......C. luteellus (Motschulsky) 5.Juxta slender, without enlargement near apex......C. izuensis Okano —Juxta enlarged near apex......C. demotellus Walker As Chilo hyrax is very closely allied to Chilo suppressalis superficially and is also attracted to light traps together with the latter species, the discovery of the species in Japan would throw various difficult problems against the control of rice stem borers, especially to detect the occurrence or to count the fluctuation of moth populations of rice stem borers. It is conceivable that many of the previous records or data on the number of moth catch at light traps might have included both individuals of Chilo suppressalis and Chilo hyrax.