Subgenus Dimetrota Mulsant & Rey, 1873

Dimetrota Mulsant & Rey, 1873: 165 (type species: Homalota tristicula Mulsant & Rey, 1873 = Homalota cadaverina Brisout de Barneville, 1860).

Coproceramius Gistel, 1857: 9 (type species: Bolitochara impressifrons Mannerheim, 1830 = Aleochara atramentaria Gyllenhal, 1810).

Engamota Casey, 1910: 151 (type species: Acrotona absona Casey, 1910).

Dimetrotina Casey, 1911: 143 (type species: Dimetrotina vaniuscula Casey, 1911).

Diagnosis. Members of the subgenus Dimetrota can be distinguished from other subgenera of Atheta by the combination of the following characters: lateral regions of body and tibiae with conspicuously long and strong setae; infraorbital carina complete; ligula divided into two lobes in basal half; pronotum with rather narrow and asperate punctation, with conspicuous and long setae in lateral margins, pubescence directed anteriorly in midline; mesocoxal cavities narrowly separated; elytra with asperate punctation; at suture subequal to length of pronotum at middle; abdomen with sparse punctation to apex; abdominal tergite II with 2 macrosetae on each side of midline, III with anterior macrosetae; macrochaetal arrangement of VII 34 (Benick & Lohse, 1974; Yosii & Sawada, 1976; Lohse et al., 1990).

Key to Korean species of Atheta subgenus Dimetrota

1. Body length less than 2.0 mm........................................................... A. (Dimetrota) furtiva

- Body length more than 2.0 mm.......................................................................... 2

2. Body length about 2.5 mm; posterior margin of abdominal tergite VIII with pointed processes......... Atheta (D.) nigripes

- Body length more than 2.5 mm; posterior margin of abdominal tergite VIII without processes or with blunt processes...... 3

3. Antennomere 3 about as long as or slightly longer than 2..................................................... 4

- Antennomere 3 slightly shorter than 2..................................................................... 9

4. Antennomere 3 slightly longer than 2; posterior margin of abdominal tergite VIII not modified; posterior margin of male abdominal tergite VIII broadly round; posterior margin of female abdominal tergite VIII subtruncate... A. (D.) photaechonica

- Antennomere 3 about as long as 2; posterior margin of abdominal tergite VIII modified, not fitting above description...... 5

5. Antennomeres 4–5 slightly elongate........................................................ A. (D.) aeneipennis

- Antennomeres 4–5 quadrate to subquadrate................................................................ 6

6. Antennomeres 7–10 transverse; posterior margin of male abdominal tergite VIII with two blunt processes in lateral regions, crenate in median region.................................................................... A. (D.) altaica

- Antennomeres 7–10 subquadrate to slightly transverse; posterior margin male abdominal tergite VIII with broad process... 7

7. Posterior margin of male abdominal tergite VIII crenate......................................... A. (D.) subsericans

- Posterior margin of male abdominal tergite VIII emarginate in median region and pointed in postero-lateral regions....... 8

8. Abdominal sternite VIII with 8 macrosetae in male (Fig. 2C), and 7 macrosetae in female (Fig. 2E) on each side of midline................................................................................... A. (D.) machonryongica

- Abdominal sternite VIII with 10 macrosetae in male (Fig. 5D), and 8 macrosetae in female (Fig. 5F) on each side of midline................................................................................... A. (D.) ovata sp. nov.

9. Body yellowish brown; antennomere 4 slightly transverse........................................... A. (D.) weisei

- Body dark brown to black; antennomere 4 about as long as wide............................................... 10

10. Posterior margin of male abdominal tergite VIII with two pointed processes in lateral regions, emarginate in median region; abdominal sternite VIII with 7 macrosetae in male, and 6 macrosetae in female on each side of midline.................................................................................................... A. (D.) atramentaria

- Posterior margin of male abdominal tergite VIII with two blunt outer processes in lateral regions and 7–9 blunt inner processes in median region (Fig. 7B); abdominal sternite VIII with 10 macrosetae in male (Fig. 7C), and 7 macrosetae in female (Fig. 7E) on each side of midline................................................................... A. (D.) yamamotoi