Laccobius, Erichson, 1837

Liu, Hsing-Che & Fikáček, Martin, 2021, Review of the Taiwanese Laccobius Erichson, 1837 (Coleoptera: Hydrophilidae) with description of a new species, Zootaxa 4963 (3), pp. 587-599 : 596

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

Figures

FIGURES 23–26. Habitat of Taiwanese Laccobius species. 23: Nantou County, Puli: habitat of L. formosus. 24: Taichung City, Wufeng: habitat of L. hammondi and L. hoi sp. nov. 25: Pingtung County, Ligang: habitat of L. formosus, L. hoi sp. nov. and L. roseiceps. 26: New Taipei City, Pingxi: habitat of L. politus.

FIGURES 19–22. Pronotum of Taiwanese Laccobius (Microlaccobius) species. 19: L. formosus Gentili, 1979. 20: L. hammondi Gentili, 1984. 21: L. hoi sp. nov. 22: L. roseiceps Régimbart, 1903.

FIGURES 10–18. Dosal view of the habitus and male genitalia of Taiwanese Laccobius species (10–13: habitus, 14–18: male genitalia). 10, 14: L. politus Gentili, 1979. 11, 15: L. formosus Gentili, 1979. 12, 16: L. hammondi Gentili, 1984. 13, 17: L. roseiceps Régimbart, 1903. 18: L. fragilis Nakane, 1966, after Nakane (1966).

FIGURES 1–5. Laccobius (Microlaccobius) hoi sp. nov., male. 1–2: habitus of the holotype (1: dorsal, 2: ventral). 3–5: aedeagus (3: dorsal view, holotype, 4: ventral view, holotype, 5: lateral view, paratype). Photos 1–2 by Uitsiann Ong.