Key to Japanese species of Aleochara (Aleochara)

1. Body large, thick, uniformly black; antennomeres I–III also black in coloration.................. A. (A.) lata Gravenhorst

-. Body small to relatively large, rather thick, not uniformly black, at most dark brown; antennomeres I–III reddish brown to brownish black....................................................................................... 2

2. Elytra uniformly yellowish to reddish brown, without any types of darkened maculations laterally and basally............................................................................................ A. (A.) coreana Bernhauer

-. Elytra uniformly yellowish to reddish brown, with darkened maculations laterally; OR elytra uniformly brownish brown (some with weak maculations laterally)......................................................................... 3

3. Elytra with prominent, blackish, and parallel sided maculations on lateral margins, reaching to each shoulder................................................................................................ A. (A.) curtula (Goeze)

-. Elytra with lateral maculations (if present), not reaching to each shoulder; OR without any maculations................. 4

4. Head rather coarsely and deeply punctured unevenly, especially near vertex; median lobe of male aedeagus narrowly elongate; female spermatheca with apical portion complicatedly coiled.................................. A. (A.) postica Walker

-. Head rather densely and shallowly punctured evenly, especially near vertex; median lobe of aedeagus bulbous; spermatheca simple, C-shaped, apical portion not coiled.................................................................. 5

5. Apical lobe of median lobe of aedeagus, not hook-shaped at apex in lateral view; spermatheca with chitinized portion of spermathecal stem moderately long, almost same length of spermathecal head and neck combined.......... A. (A.) parens Sharp

-. Apical lobe of median lobe of aedeagus, moderately hook-shaped at apex in lateral view; spermatheca with chitinized portion of spermathecal stem long, almost 1.5 times as long as spermathecal head and neck combined; endemic to Ishigaki-jima Is. and Iriomote-jima Is., Yaeyama-shotô Islands, southwestern part of Japan ........................ A. (A.) yaeyamensis n. sp.