Viettherchnus helferi, Jelínek & Hájek, 2024

Jelínek, Josef & Hájek, Jiří, 2024, Three new species of the genus Viettherchnus Kirejtshuk, 1985 (Coleoptera: Nitidulidae: Nitidulinae: Cyllodini), Zootaxa 5519 (4), pp. 590-600 : 596-599

Viettherchnus helferi sp. nov.

( Figs. 3 , 7 , 9 , 12, 15, 17 )

Type material. Holotype ♂ (NMPC), labelled: “ INDONESIA, E KALIMANTAN /ca. 50 km W of BALIKPAPAN / PT Fajar Surya Swadaya [area] / 01°13.4′S, 116°22.6′E, 66 m / J. Hájek, J. Schneider & / P. Votruba leg., 27+ 30. xi.2011 [p] // stream in primary rainforest /ca 2 m wide sandy+mud bottom / collecting in stream and tributaries / on vegetation and dead wood [p] // HOLOTYPUS ♂ / VIETTHERCHNUS / helferi sp. nov. / JelÍnek & Hájek det. 2024 [red label, p]” . Paratypes: 20 ♂, 19 ♀, the same data as holotype ( NMPC) ; 1 ♂, “ MALAYSIA-Perak / Banjaran Bintang / Bukit Berapit ( Taiping ) / 11.- 12.3.1997 / Ivo Jeniš leg. [p]” ( NMPC) ; 1 ♂, “MUS.PRAGENSE / TENASSERIM / COLL.HELFER [p]” ( NMPC). All paratypes with the appropriate printed red label .

Description of male holotype. Habitus. Broadly oval, convex, glabrous, smooth and shining.

Colouration. Black, sides and base of pronotum with narrow reddish border, disc of pronotum with pair of vaguely delimited reddish spots. Disc of elytra orange, humeral bulges, sides and apex of elytra black. Ventral surface red-brown. Clypeus, legs and antennae brown-yellow, antennal club black ( Fig. 4 ).

Head across eyes narrower than anterior margin of pronotum. Frons almost flat, between antennal insertions with sharp transverse edge projecting over basal portions of clypeus, arcuate in middle and with blunt prominent teeth laterally besides antennal insertions. Punctures of frons fairly equal in size to eye-facets, separated by 1.0– 1.5 diameters, interspaces indistinctly alutaceous. Clypeus flat, situated markedly beneath level of frons, truncate anteriorly, alutaceous with a few dispersed shallow punctures. Labrum subtruncate anteriorly with small shallow incision.Mandibles abruptly curved, outer margins arcuate, sharp, raised over shallowly bifid apex, on right mandible ending in short prominent tip ( Fig. 7 ). Antennae slightly longer than width of head across eyes (ratio HEAW/ANLE = 0.96), antennal club occupying ca. one third of antenna length, distinctly shorter than antennomeres II–VIII combined, 1.64× longer than wide, widest at distal end of antennomere IX. Scapus ca. 1.7× longer than wide, almost twice as wide as pedicel. Antennomere III twice as long as wide, IV and V subequal, somewhat longer than wide, VI as long as wide, VII and VIII transverse, VIII wider than preceding ones, adjacent to club.

Pronotum convex, widest at posterior angles, arcuately narrowed anteriad, ratio WPR1/WPR3 = 1.94, WPR1/ LEPR = 1.83. Anterior margin trapezoidal, not bordered, anterior angles obtusely angulate, blunt. Lateral margins broadly arcuate, finely bordered, not explanate. Basal margin not bordered, in middle projecting into broad short truncate lobe concealing basal portion of scutellar shield, at sides broadly arcuate. Posterior angles obtusely rounded without well-defined tips. Surface of pronotum vaulted both longitudinally and transversely, punctate like frons. Scutellar shield large, subtriangular with rounded apex, punctate like pronotum.

Elytra almost as long as their combined width (ratio LELY/WELY = 0.98), widest somewhat behind humeral angles and gradually arcuately narrowed posteriad, simultaneously rounded apically. Lateral margins finely bordered, not explanate, not visible simultaneously in their entirety (dorsal view). Surface strongly convex with distinct traces of rather irregular series of punctures; punctures almost equal in size to those of pronotum, within one series separated by more than one diameter. Interstries with smaller and widely spaced diffuse punctures. Interspaces feebly alutaceous.

Ventral side. Antennal furrows converging posteriad. Prosternum very short with sharp mediolongtudinal carina vanishing at distal end of prosternal process, coarsely and densely punctate. Apical margin of prosternal process blunt, subtruncate. Hypomera concave, indistinctly sparsely punctate, moderately shining, with raised sharp ridge nearly parallel to basal margin of pronotum. Mesoventrite roof-shaped, impunctate with fine mediolongitudinal carina. Mesocoxal axillary lines arcuate, running close to posterior margin of mesocoxal cavity. Metaventrite broadly and flatly transversely vaulted; its anterior intercoxal process broad, bordered, anterior margin shallowly concave, overlapping base of mesoventrite with anterior lateral angles somewhat prominent; posterior intercoxal margin truncate. Surface with punctures equal in size to eye-facets, separated by 1.0–1.5 diameters, interspaces obsoletely alutaceous. Discrimen absent. Metacoxal axillary lines arcuate, running close to posterior margin of metacoxal cavity. Abdominal ventrites punctate like metaventrite, punctures closer, mostly separated by less than one diameter ( Fig. 9 ).

Legs. Profemur 1.5× longer than wide, its anterior margin rectilinear, proximal anterior angle rectangular; ventral surface with fine longitudinal carina in posterior half. Protibia ca. 2.5× longer than wide, subparallel-sided; outer subapical angle rectangular, outer margin densely denticulate, dorsal surface with dense and coarse punctures bearing semierect bristles, ventral surface with irregular longitudinal series of minute spines. Protarsomeres I–III 0.75× the width of protibia, V as long as I–IV combined. Meso- and metafemur broadly oval, 2.00× and 1.85× longer than wide respectively. Meso- and metatibia almost 3× longer than wide, in basal third abruptly dilated distally, then almost parallel-sided. Tarsal claws simple.

Male genitalia. Penis broadly oval, in distal third gradually narrowed towards bluntly pointes apex ( Fig. 12 ). Tegmen oval, broadly rounded apically ( Fig. 15 ).

Female. Habitus as in male, from which it differs in frons and clypeus in the same plane, separated by indistinct transverse depression; frontoclypeal suture absent; punctures on clypeus markedly finer than those of frons. Mandibles and scapus simple, not expanded. Protarsomeres I–III narrower, 0.6× the width of protibia. Exposed posterior margin of tergite VIII absent. Ovipositor serrate in apical third, apex acutely pointed, without styli ( Fig. 17 ).

Variation. Colour of pronotum and disc of elytra sometimes dark red to nearly black, extent of red colouration sometimes more or less reduced ( Fig. 3 ); specimens with darker colouration prevail in the type series. Reddish sides of pronotum sometimes more extended mesad.

Measurements. Body length 2.4–3.0 mm (holotype 2.95 mm), width 1.7–2.0 mm (holotype 1.95 mm), height 1.1–1.5 mm (holotype 1.50 mm).

Differential diagnosis. Antennal club shorter than antennomeres II–VIII combined resembles conditions in Viettherchnus plagiatus and V. orszuliki sp. nov. Viettherchnus helferi sp. nov. differs from them in different colour pattern (elytra without several ligter spots), and in male sex in anterior margin of frons expanded anteriad to overlap basal portion of clypeus.

Collection circumstances. At the type locality in East Kalimantan, V. helferi sp. nov. was collected from unidentified fungi growing on the bottom side of dead tree trunk fallen over small stream in remnant of lowland primary rainforest ( Fig. 18 ).

Name derivation. The new species is dedicated to the Bohemian physician, explorer and naturalist Johann Wilhelm Helfer also known as Jan Vilém Helfer (1810–1840). He was probably the first, who collected in 1837– 1839 plants and animals in Tenasserim ( Myanmar), among them also one paratype of the new species. After his sudden death on Andaman Islands (January 30 th, 1840), his widow, Pauline Helfer donated her husband’s collections to the Bohemian Museum, nowadays the National Museum, Prague. The specific epithet is a noun in the genitive case.

Distribution. Viettherchnus helferi sp. nov. seems to be widespread species, currently it is known from Indonesia (Kalimantan), Malaysia (Perak), Myanmar (Tenasserim).

Figures

FIGURE 18. Habitat of Viettherchnus helferi sp. nov. at the type locality (Indonesia, Eastern Kalimantan, PT Fajar Surya Swadaya).

FIGURES 1–4. Dorsal habitus of Viettherchnus. 1. V. orszuliki sp. nov. (holotype ♂); 2. V. apriculus sp. nov. (holotype ♂); 3. V. helferi sp. nov. (paratype ♀, dark form; Kalimantan); 4. V. helferi sp. nov. (holotype ♂). Scale bar 1 mm.

FIGURES 5–7. Head of male Viettherchnus. 5. V. orszuliki sp. nov.; 6. V. apriculus sp. nov.; 7. V. helferi sp. nov. Not in scale.

FIGURES 8–9. Ventral habitus of Viettherchnus. 8. V. orszuliki sp. nov. (paratype ♂); 9. V. helferi sp. nov. (paratype ♀; Kalimantan). Scale bar 1 mm.

FIGURES 10–17. Genitalia of Viettherchnus. 10–12. penis with internal sac in dorsal view; 13–15. Tegmen; 16–17. Ovipositor. 10, 13, 16. V. orszuliki sp. nov.; 11, 14. V. apriculus sp. nov.; 12, 15, 17. V. helferi sp. nov. Scale bar 0.5 mm.