Laccobius (Microlaccobius) roseiceps Régimbart, 1903 RẦflǿ

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 : 595-596

Laccobius (Microlaccobius) roseiceps Régimbart, 1903 RẦflǿ 牙ḃ

( Figs 13, 17 , 22 , 25 )

Laccobius (Microlaccobius) roseiceps Régimbart, 1903: 59 .

Material examined. TAIWAN: PINGTUNG: 3 males, 6 females ( HCLC): Ligang Township [¶ffiė], Erchong River [二AEë], 22.7982°N 120.5011°E, 32m 26.IV.2019 . Hsing-Che Liu . KAOHSIUNG: 1 spec. ( HCLC): Liouguei District [六AE區], Laonong River [Ž濃ë], 22.996017°N 120.638178°E, 229m, 24.VI.2020. Hsing-Che Liu & Uitsiann Ong leg. KINMEN: 2 males, 20 spec. ( HCLC, NCHU): Main Island , 5-10. VII. 2020, Hsing-Che Liu leg.

Diagnosis. Small species, body length 1.7–2.2 mm, body width 1.0– 1.3 mm. Body elongate oval ( Fig. 13 ), weakly convex. Head dark, with distinct preocular spots. Pronotum pale, with small dark oval spot in median, spot leaving large lateral portions of the pronotum yellow. ( Figs. 22 ). Scutellar shield dark. Elytra pale, with densely arranged small dark spots, larger spots present medially and laterally. Leg pale or yellowish. Male genitalia ( Fig. 17 ): Aedeagus 0.4 mm long. Median lobe wide, its apex rounded, with a pair of diverging lines running from apex; parameres slender, larger than median lobe, slightly bent inward.

Differential diagnosis. Laccobius roseiceps may be easily recognized by the pronotum with small oval dark spot. In this character, it may resemble L. hoi sp. nov. from which it mainly differs in smaller body size (1.7–2.2 mm in L. roseiceps , 2.5–2.7 mm in L. hoi sp. nov.). The structure of the median lobe (with the diverging lines) is very typical and hard-to-confuse with any other Laccobius species.

Distribution. China ( Hong Kong), Japan (Honshu, Kyushu, Tanegashima), Taiwan (Kinmen islands) ( Nakajima et al. 2020; Przewoźny, 2020, Liu et al. 2021). First record for Taiwan island ( Fig. 27 ).

Bionomics. All specimens were collected from very slowly running streams. In southern Taiwan, the species co-occurred syntopically with L. hoi sp. nov. and L. formosus ( Fig. 25 ).

Figures

FIGURES 27. Map of Taiwan showing the distribution of the Laccobius species.

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 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 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.