Viettherchnus, Kirejtshuk, 1985

Jelínek, Josef & Hájek, Jiří, 2024, Three new species of the genus Viettherchnus Kirejtshuk, 1985 (Coleoptera: Nitidulidae: Nitidulinae: Cyllodini), Zootaxa 5519 (4), pp. 590-600 : 599-600

Key to the species of Viettherchnus (modified after Kirejtshuk & Kirk-Spriggs 1996)

1. Black with red pattern on elytra. Antennal club shorter than antennomeres II–VIII combined......................... 2

- Body ± unicolorous, sometimes with indistinct lightening on disc of pronotum or elytra; if bicoloured, then without several separated spots on elytra. Length of antennal club various..................................................... 3

2. Black with two small bright red spots on each elytron. Male: mandibles with long and flat subparallel-sided projections bluntly rounded apically; scape with anterior margin rounded, medially projected. Body length: 2.5–2.9 mm. Malaysia........................................................................ V. plagiatus Kirejtshuk & Kirk-Spriggs, 1996

- Typically orange-red, pronotum with four black spots, elytra with several black spots. In specimens with most extended black pigmentation pronotum mostly black with orange borders at sides and lateral portions of basal margin, as well as with more or less interrupted zigzag transverse bar on disc; elytra black, each with large orange ellipse in sutural half, reaching from basal margin to ca. 2/3 of elytra length and projecting shortly laterad, also humeral angle orange. Male: mandibles arcuately dilated laterally with sharp, raised angulate dorsal edge; scape with anterior margin rounded, medially subangulate. Body length: 2.4–3.0 mm. Nepal.................................................................... V. orszuliki sp. nov.

3. Antennal club shorter than antennomeres II–VIII combined. Black; disc of elytra orange, sides and apex black. Male: anterior margin of frons extended forwards, overlapping basal portion of clypeus. Body length: 2.4–3.0 mm. Indonesia (Kalimantan), Malaysia (Perak), Myanmar (Tenasserim).................................................... V. helferi sp. nov.

- Antennal club as long as or longer than antennomeres II–VIII combined......................................... 4

4. Elytra without distinct longitudinal series of punctures. Punctation of dorsum especially fine, particularly on elytra. Elytra separately rounded apically. Antennal club ca. 1.3× longer than wide. Male: mandibles with slightly raised lateral projections; scapus with anterior margin rounded. Body length: 2.1 mm. Philippines (Mindanao).... V. philippinensis Kirejtshuk, 1987

- Longitudinal rows of punctures on elytra ± distinct. Sutural angle between apices of elytra less distinct. Dorsum more coarsely punctate. Antennal club at least 1.5× longer than wide........................................................ 5

5. Antennal club narrower, slightly wider than tibiae, not longer than antennomeres II–VIII combined. Male: mandibles with strongly raised rounded lateral projections; scapus with anterior margin rounded. Body length: 2.6–2.9 mm. Vietnam, southern India........................................................................ V. finitimus Kirejtshuk, 1985

- Antennal club comparatively larger, in the widest part about 1.5× wider than tibiae, as long as antennomeres II–VIII combined or longer............................................................................................ 6

6. Elytra brightly orange with black sides and apex. Frons without any concavity. Male: mandibles with striking, acutely pointed projections curved outwards; scapus with anterior margin rounded. Body length: 2.4 mm. Malaysia (Perak)................................................................................................. V. apriculus sp. nov.

- Almost unicolorous chestnut brown. Frons with distinct concavity. Male: mandibles with lateral margin of each projection angulate, apices bluntly pointed, turning up abruptly at half their length; scapus with anterior margin angulate. Body length: 2.3–3.0 mm. Indonesia (Sulawesi), Philippines (Luzon)............. V. sulawesiensis Kirejtshuk & Kirk-Spriggs, 1996