Ancyronyx pulcherrimus, Kodada, Ján, Jäch, Manfred A. & Jr, Fedor Čiampor, 2014

Kodada, Ján, Jäch, Manfred A. & Jr, Fedor Čiampor, 2014, Ancyronyx reticulatus and A. pulcherrimus, two new riffle beetle species from Borneo, and discussion about elmid plastron structures (Coleoptera: Elmidae), Zootaxa 3760 (3), pp. 383-395 : 386-391

Ancyronyx pulcherrimus sp.n.

Type locality. Borneo, Brunei, Belait District, Sungai [river] Ingei, forest pool, 04°09'15''N 114°43'04''E.

Type material. Holotype ♂ (BM): “ BRUNEI: Belait Distr. Sg. Ingei, forest pool near Base Camp, 14.VI.2010 N04°09'15'' E114°43'04'' leg. Mayyer Ling (34)”. Paratypes ( NMW, UB): 1 ♂ and 2 ♀♀, same locality data as holotype.

Description. Habitus as in Fig. 4 . Body form elongate, elytra moderately convex dorsally. BL: 1.84–2.00 mm in ♂♂, 1.96–2.00 mm in ♀♀; EW: 0.80–0.88 mm in ♂♂, 0.80–0.84 mm in ♀♀; BL/EW: 2.30–2.72 in ♂♂, 2.38– 2.45 in ♀♀. Colouration pattern as in Fig. 4 . Labrum black on lateral thirds, yellowish on middle third; mouth parts and antennae yellowish, except of brownish terminal antennomere; clypeus and frons yellowish, yellowish portion triangularly narrowed posteriad, rest of head black dorsally and posteriad of eyes; pronotum yellowish except large mesal black spot on anterior third; scutellum yellowish; elytra black, medially with extensive, nearly X-shaped yellowish pattern, apices yellowish; venter yellowish except of black mesanepisterna, metanepisterna, lateral portion of metaventrite and lateral portions of ventrites 1–5; coxae yellowish; femora yellow with black band between middle and proximal fourth; tibiae black on proximal three fourths, yellowish on distal fourth; tarsomeres basally dark brown, distally yellowish; claws pale reddish brown distally. Plastron structures similar to those in A. reticulatus .

Head. Labrum about as long as clypeus, anterior margin more or less straight, surface finely punctate, smooth between punctures, setae fine and distinct. Clypeus, frons and vertex finely punctate and granulose, granules elongate, tiny; surface between granules reticulate, reticulation more distinct on black portion of vertex; frontoclypeal suture nearly straight, finely impressed. Eyes moderately protruding. Antennae 11-segmented, slender, nearly as long as pronotum. Genae microsculptured; gula smooth, gular sutures fine, mesally narrowly separated. HW: 0.44–0.48 mm in ♂♂, 0.44–0.48 mm in ♀♀; ID: 0.24–0.26 mm in ♂♂, 0.25–0.26 mm in ♀♀.

Thorax. Pronotum distinctly wider than long (PL/MW: 0.77 in ♂♂, 0.79 in ♀♀), widest near posterior angles; anteriorly attenuate, anterior margin arcuate; lateral pronotal carina absent, hypomeral portion visible in dorsal view; anterior transverse groove distinctly impressed, oblique and dividing pronotum, area posteriad of transverse groove gibbous on each side; anterior mesal longitudinal carina hardly discernible; posterolateral oblique grooves feebly impressed. Pronotal surface punctate, reticulate anteriorly, interstices smooth on disc and posteriorly; punctures shallowly impressed, irregular in shape, distinctly larger than facet diameter, nearly confluent, denser on disc and anteriorly than in posterolateral portion, bottom of anterior punctures reticulate; PL: 0.56–0.60 mm in ♂♂, 0.62 mm in ♀♀, MW: 0.72–0.78 mm in ♂♂, 0.78 mm in ♀♀. Prosternum irregularly, densely and roughly punctate, very short in front of procoxae; prosternal process distinctly transverse, medially slightly impressed, posterior margin widely rounded, feebly protruding posteriad. Scutellum subpentagonal, surface smooth and shiny. Elytra elongate, EL: 1.30–1.40 mm in ♂♂, 1.38–1.40 mm in ♀♀, EL/EW: 1.59–1.63 in ♂♂, 1.66–1.73 in ♀♀, subparallel along anterior 0.1–0.7, then tapering posteriad to separately rounded apices; with ten more or less regular striae, seven striae between suture and shoulder, 4–5 punctures in accessory scutellary rows; punctures large, round and deeply impressed on disc, smaller and less distinct anteriorly; interstices and intervals wider and flat on disc, narrower and feebly convex laterally and posteriorly, nearly glabrous; humeri moderately prominent. Mesoventrite flat, approximately half as long as prosternum, mesoventral cavity shallow, surface irregularly densely punctate and microreticulate, mesoventral discrimen absent. Metaventrite about as long as prosternum and mesoventrite combined, disc with shallow longitudinal depression mesally, metathoracic discrimen visible; surface punctate, granulate and microreticulate, punctures coarser and denser laterally than on disc. Hind wings not examined. Forelegs about 1.6 times as long as body; pro- and mesocoxae large and prominent, bluntly dropshaped; metacoxae smaller and less protruding laterally; femora, tibiae and tarsi with short setae, tibiae with few additional longer setae; distal tarsal segments with several longer setae near apex; claws large, base with three teeth, basal one very small and indistinct.

Abdomen. Abdominal intercoxal process as long as ventrite 1 posterior to metacoxae, very wide, rounded anteriorly; ventrite 1 longest, ventrite 2 ca. 0.6 times as long as ventrite 1, ventrite 3 ca. 0.7 times as long as ventrite 2, ventrite 4 ca. 0.8 times as long as ventrite 3, ventrite 5 ca. as long as combined length of ventrites 4 and 3. Surface of ventrites with large shallow punctures and setigerous flat smooth transverse granules; punctures more distinct and widely separated on mesal portion of ventrites, granules more prominent and more conspicuous laterally, ventrite 5 granulate only. Male sternite IX ( Fig. 38 ) ca. 460 Μm long; apical margin moderately deeply emarginate, lateroapical portion with microsetae and cluster of pores; paraprocts not reaching apical margin. Tergite VIII in both sexes finely reticulate, with conspicuous median transverse ridge separating posterior and anterior portion; basal half with microtrichial pattern; apical margin hyaline, subapical fringe of hair-like setae present, setae on sublateral portions stronger and longer than those along margin.

Aedeagus ( Figs 36, 37 , 41) ca. 450 Μm long; penis about 2.3 times as long as phallobase, sides subparallel along basal half, gradually tapering apicad, subapically distinctly curved ventrad (lateral view), with numerous short but distinct setae on dorsolateral portion; ventral sac large; fibula conspicuous, wide; corona well developed; endophallus without spinules; basolateral apophyses moderately long and slender. Phallobase asymmetrical; parameres almost reaching apex of penis, widest near base, narrowest near middle, ventral margin distinctly sinuous, apex wide (all in lateral view); mesal and outer surface of parameres with spinules arranged in short longitudinal rows.

Ovipositor (Fig. 40) ca. 460 Μm long; stylus slender, outer margin slightly bent outwards, inner margin nearly straight (dorsal view). Coxite moderately long and stout, posterolateral angle rounded, not protruding, distal portion ca. 1.8 times as long as wide, with several rather short and wide, peg-like setae; inner margin moderately pubescent; basal portion distinctly shorter than distal portion, with peg-like and hair-like setae, most densely set laterally. Valvifer longer than coxite, apical margin with hair-like setae.

Sexual dimorphism. Longitudinal depression of metaventrite deeper and larger in males than in females. Ventrite 5 in females longer and narrower. Anterior median strut of sternite VIII in females longer.

Differential diagnosis. The general habitus and colour patterns of this species resemble A. helgeschneideri from which it can be distinguished by: 1) wide black band on each femur; 2) granules on dorsal surface of head less prominent; 3) pronotum with anterior mesal longitudinal carina hardly discernible; 4) anterior transverse groove of pronotum less impressed; 5) dark spot posteriad of anterior transverse groove of pronotum absent; 6) surface of elytra smooth and somewhat shiny; 7) yellowish pattern on elytra larger; 10) penis with short but distinct setae on dorsolateral portion; 11) parameres narrowest near middle, dorsal and ventral margin sinuous; 12) apex of parameres wide.

Ancyronyx reticulatus , described above, differs from A. pulcherrimus in: 1) larger size; 2) less elongate and wider body; 3) different elytral colour pattern; 4) entirely yellowish femora; 5) distinct anterior mesal carina of pronotum; 6) reticulate and matt elytra; 7) entirely reticulate metaventrite disc; 8) nearly confluent punctures on ventrites; 9) penis with a few very short indistinct setae dorsally; 10) penis ca. twice as long as phallobase; 11) distal portion of coxite only 1.1 times as long as wide.

General habitus and colour patterns of A. pulcherrimus also resemble A. malickyi , a species wide-spread in SE Asia, being also recorded from Borneo. However, in A. malickyi there are always two dark spots on every femur.

Variability. Specimens examined show little variability in the size of the X-shaped yellowish pattern on the elytra and in the intensity and size of the black spots on the ventrites.

Distribution. This species is known only from the type locality in Brunei.

Etymology. Adjective, pulcherrimus , superlative of pulcher (Latin)—very beautiful. Named in reference to the beautiful colour pattern of this species.

Figures

FIGURES 1 – 4. Dorsal habitus of 1) Ancyronyx reticulatus, male, holotype; 2) A. reticulatus, female, paratype; 3) A. helgeschneideri, male, paratype; 4) A. pulcherrimus, male, paratype. Scale bar 0.5 mm.

FIGURES 36 – 38, 40, 41. Ancyronyx pulcherrimus: 36) aedeagus, ventral view; 37) same, dorsal view; 41) same, lateral view; 38) male sternite IX; 40) ovipositor, ventral view. FIGURE 39. A. reticulatus, ovipositor, ventral view. Scale bar 0.1 mm.