Key to Taiwanese species of Laccobius

1. Eyes kidney-shaped (reniform). Antenna with 7 antennomeres (subgenus Glyptolaccobius). Legs brown. Inhabits wet rocks (Fig. 26).......................................................................... L. politus Gentili, 1979

- Eyes rounded. Antenna with 8 antennomeres (subgenus Microlaccobius). Legs pale yellowish. Inhabits sides of streams or ponds or sun-exposed algal mats (Figs. 23–25).............................................................. 2

2. Body small (1.7–2.2 mm), elongate oval. Pronotum with a small central dark oval spot which is narrower than the width of the head (Fig. 22)................................................................. L. roseiceps Régimbart, 1903

- Body larger (2.0– 2.8 mm), oval. Pronotum with much bigger dark spot, as wide as head or wider...................... 3

3. Parameres widened and membranous apically, median lobe distinctly shorter than parameres.......................... 4

- Parameres slender, bent inward in apical third, median lobe slightly shorter than parameres or as long as parameres....... 5

4. Median lobe wider, apical broadly rounded (Fig. 15)..................................... L. formosus Gentili, 1979

- Median lobe narrower, apical strongly narrowing (Fig. 18)................................. L. fragilis Nakane, 1966

5. Pronotum with a dark spot slightly wider that the head (Fig. 22). Median lobe of the aedeagus very broad, moderately narrowing apically (Fig. 3–4), Parameres very narrow in dorsal and ventral views (Fig. 5).......................... L. hoi sp. nov.

- Pronotum almost entirely dark, with pale lateral margins (Fig. 20). Median lobe of the aedeagus widening in the midlength, apex subtruncate. Parameres narrow in dorsal view (Fig. 16).............................. L. hammondi Gentili, 1984