Bathythrix genus group

(subtribe Bathytrichina sensu Townes (1970))

Two genera, Bathythrix Förster, 1869 and Retalia Seyrig, 1952, have been recorded from Japan. In addition, I found Surculus from Japan. In this study, I newly record this genus from Japan and review Bathythrix and Retalia . The Japanese genera can be distinguished by the following key.

Key to Japanese genera of Bathythrix genus group

1. Notaulus short, not reaching to center of mesoscutum, its ending abruptly at a weak pit (Fig. 63E). Body relatively small, fore wing shorter than 3.5 mm. ………………………………… Retalia Seyrig, 1952

-. Notaulus long, at least reaching to center of mesoscutum, its end without pit (Figs 63D, F). Body relatively large, fore wing usually longer than 3.5 mm. ……………………………………………………… 2

2. Notaulus fading out near center of mesoscutum (Fig. 63F). T I with its spiracle near the basal 0.45 (Fig. 65X). Anterior section of lateral longitudinal carina of propodeum absent (Fig. 64A). ……………………………… Surculus Townes, 1970

-. Notaulus ending abruptly far behind center of mesoscutum (Fig. 63D). T I with its spiracle usually beyond the middle. Anterior section of lateral longitudinal carina of propodeum present. ……………………………… Bathythrix Förster, 1869