Grouvellinus nigerquadratus Freitag, Molls and Bouma, 2019Grouvellinus cruxniger Freitag, Molls and Bouma, 2019Grouvellinus luciaensis Freitag, Molls and Bouma, 2019Grouvellinus borneensis Freitag, Molls and Bouma, 2019

Freitag, Hendrik, Molls, Christian, Bouma, Aglaia M., Garces, Jhoana M., Rossato, Marzia, Cosentino, Emanuela & Delledonne, Massimo, 2019, Additional new species of Grouvellinus Champion 1923 (Insectaı Coleopteraı Elmidae) discovered by citizen scientists and DNA barcoded in the field applying a novel MinIONbased workflow, JOURNAL OF NATURAL HISTORY 53 (41), pp. 2593-2620 : 2597-2616

Grouvellinus andrekuipersi Freitag, Pangantihon and Njunjić, 2018

( Figure 2 )

Grouvellinus andrekuipersi ; Freitag et al. 2018: 13 – 19, figures 4, 9, 10 (orig. descr.).

Material examined. 13, 2exs. (SP) ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’; Paratypes: 13 [H13], 2 exs. (SP) ‘ MALAYSIA: Sabah: Lucia River; root packs, riffle; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6h)M ’; 1 3 [H19], 1 ♀ (BOR/COL) ‘ MALAYSIA: Sabah: Maliau Basin: Giluk River; Cryptochorinae water plants, run; ca. 4° 44 ʹ 36 ʹʹ N, 116°52 ʹ 21 ʹʹ E, ca. 980m a.s. l. 01.X.2017, leg. H. Freitag, C.V. Pangantihon & I. Njunjić (GilR2r) ’.

Remarks

The specimens agree well with the type material from the Maliau Basin. The specimens from Tawau tend to be very slightly slenderer, 2.05 times as long as wide (CL/EW). From all other Bornean Grouvellinus species, it varies most conspicuously in the aedeagal character. Among the known species from Borneo, it is of medium size (1.7 – 1.8 mm CL), with distinct pronotal characters (moderately sparsely punctate; punctures very small and shallowly impressed; setae moderately long; interstices glabrous and flat; sublateral carinae very indistinct and short; oblique impression moderately deep and narrow, laterobasal impression indistinct). It belongs to an almost cryptic species group with two pairs of more or less conspicuous yellowish elytral spots.

The first mtDNA barcodes for the species are presented here ( LR738835 , LR738833 ). The species varies at least by 6.6% genetic distance (654bp CO1 barcode) from the most similar Bornean congener G. nigerquadratus sp. nov.

Distribution

Grouvellinus andrekuipersi is known only from Borneo Island ( Freitag et al. 2018), namely the upper Maliau Basin, Tawau Hills Park, and Crocker Range in Sabah and two sites in eastern Sarawak ( Figure 18 ).

Grouvellinus nigerquadratus Freitag, Molls and Bouma , sp. nov.

( Figures 3, 4 , 10 (a – c), 11(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (e)).

Type material. Holotype 3 [H56] (SP): ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1c)M ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 23, 1♀ [H16] (SP) same data as holotype; 2 exs. ‘ MALAYSIA: Sabah: Tawau River; rock surface, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1g)M ’; 1♀ (SP) ‘ MALAYSIA: Sabah: Tawau River; rock surface, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1f)M ’ . Other material: 13, 1♀ (SP) same data as holotype; 13 (SP) ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s. l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’.

Etymology

The epithet refers to the elytral colour pattern which appears like an oblique black square especially in pale specimens with distinct yellowish markings.

Description

Body elongate, males 1.50 – 1.55 mm, females 1.65 – 1.75 mm long (CL); males 0.74 – 0.78 mm, females 0.78 – 0.88 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figures 3, 4 ) dominantly dark brown; pronotum black, anterior margin slightly paler, golden-brown; entire median transverse portion of elytra including disc dark brown; peripheral elytral portions with two pairs of more or less distinct, extended yellowish-brown spots; basal pair between lateral margin and first row of punctures subtrapezoidal; subapical spots between lateral margin and suture obliqueoval; coxae, femora and tibiae dark brown, areas near articulations usually slightly paler; tarsi and antennae golden brown; maxillary and labial palps dark brown; pubescence yellowish. Ventral side ( Figure 10 (b,c)) dark brown.

Head ( Figure 10 (a)) 0.35 – 0.39 mm wide (HW); ID 0.16 – 0.17 mm; frons, clypeus, and labrum moderately pubescent; punctures small; intervals medially flat and glabrous, laterally rugulose. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical, usually semicircularly folded around anteriolateral eye margin.

Pronotum ( Figure 10 (a)) in males 0.48 – 0.50 mm, in females 0.48 – 0.54 mm long (PL); in males 0.57 – 0.61 mm, in females 0.61 – 0.67 mm wide (PW), wider than long (PL/PW), widest posterior 0 – 0.4, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly convex, anterior angles obtuse, rounded, slightly protruding; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures very small and shallowly impressed; setae moderately long; median carina absent; pair of short posteriomedian patches conspicuous; sublateral carinae short, rather indistinct; oblique impression moderately shallow and narrow, extending approximately anterior 0.3 – 0.7; laterobasal impression shallow; disc, entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; lateral submarginal area, laterobasal and oblique impressions rugose. Hypomeron very densely punctate.

Prosternum ( Figure 10 (b)) moderately long; lateral portions appearing rugulose, with inconspicuous pubescence (plastron); anteriomedian portion inconspicuously transversely micro-reticulate, almost glabrous; prosternal process subtrapezoidal, slightly shorter than as wide at the base, medially somewhat irregularly impressed, rugulose; posterior margin convex; angles gently rounded. Scutellum ( Figure 10 (a)) subtriangular, medially slightly impressed, glabrous.

Elytra ( Figures 3, 4 ) elongate, moderately convex dorsally. EL: males 1.05 – 1.15 mm, females 1.15 – 1.24 mm; ca. 1.45 times as long as wide (EL/EW), widest at the middle, subparallel from anterior 0.2 to 0.6, subconical towards apices; apices moderately narrow, separately rounded; with eight longitudinal, slightly impressed rows of primary punctures; primary punctures regularly arranged, large (approximately as wide as intervals) and deeply impressed anterior of clivity and in anterolateral portions, small (0.1 – 0.3 times of intervals) and shallowly impressed apicad of clivity and at most basal portion; interstices slightly rugose; intervals with additional, very inconspicuous setiferous secondary punctures; pubescence yellowish, somewhat regularly arranged along intervals, consisting of sparse, large erected setae, and moderately large adpressed setae; interval 8 with distinct, interval 7 with indistinct serrate carinae; interval 2 neither carinate nor elevated; lateral elytral margin distinctly serrate (at least in basal half).

Mesoventrite ( Figure 10 (c)) with two pairs of deep grooves, the median pair obliquely oval in males, subquadrate in females (somewhat varying in some specimens, see comments below). Metaventrite ( Figure 10 (c)) with median groove and most anterior portion somewhat glabrous; remaining disc with irregularly uneven surface and moderately densely covered with setiferous tubercles; longitudinal impression moderately deep, widely impressed, reaching ca. posterior two-thirds in males, and one-half in females; portions adjacent to disc and coxae with irregular, rugose impressions, punctures and tubercles, but without any distinct hair patch; most lateral portions densely punctate and with plastron.

Ventrite 1 ( Figure 10 (c)) with pair of longitudinal carinae; discs of ventrites 1 and 2 mainly glabrous, but with sparse regularly arranged long trichoid setae; ventrite 3 glabrous medially; lateral portions of ventrites 1 – 3 and almost entire ventrites 4 – 5 ( Figure 10 (c)) densely covered with plastron and scattered, moderately long setae; the latter more dense at apex and lateral margins of ventrite 5.

Legs ( Figures 3, 4 ) all approximately of the same length and slightly longer than body; tibiae longer than tarsi and femora; inner and outer ventral margin of all tibiae with longitudinal row or patch of long trichoid setae (in both sexes); faces of femora and tibiae very densely covered with plastron-like setae and some longitudinally arrange long trichoid or spine-like setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 11 (a,b)) ca. 590 μm long, medially ca. 105 μm wide. Base reaching basal 0.45 of total aedeagus length. Median lobe ca. 4.5 times as long as wide, moderately overreaching parameres, moderately conical towards broadly rounded apex in apical third. Ventral sac inflated ventrad, internally densely covered with long, thin spines that reach the apical opening. Parameres very slender (lateral view), laterally inflated (ventral view), apically conical, pointed (in both, ventral and lateral view), usually with slightly more than 10 trichoid setae in apical third, most of them at outer ventral face; most apical two setae longest and inserted at dorsolateral face, medioventral portion moderately densely covered with scattered very short, acute setae.

Ovipositor ( Figure 11 (c)) total length ca. 570 μm; stylus ca. 42 μm long, straight with ca. three short sensilla; coxite ca. 280 μm long, moderately densely and evenly covered with very short, acute setae; proximal portion distinctly longer than wide and distinctly overlapping with slender distal portion, apically distinctly roundly broadened at outer margin and with three or more hook-like sensilla; valvifer 295 μm long, caudal portion slightly sclerotised and with a few scattered, very short, acute setae; fibula almost straight.

Differential diagnosis

Grouvellinus nigerquadratus sp. nov. is similar to G. andrekuipersi especially in the yellowish elytral patterns commonly observed in pale specimens, but the extension of these elytral patterns is usually larger in the new species. G. nigerquadratus sp. nov. can be distinguished from G. andrekuipersi by the generally slightly smaller size (CL 1.50 – 1.75 mm vs. 1.7 – 1.8 mm), the pronotum with obtuse anterior angles (vs. protruding acute angles), the large (approximately as large as interstices) and deeply impressed elytral punctures in striae 4 and 5 anterior of clivity. From all known Bornean Grouvellinus spp. it can be distinguished by its very slender aedeagus with apically distinctly pointed and laterally inflated parameres that are covered with very short, acute setae in medioventral portions. The species varies at least by 6.3% genetic distance (654 bp CO1 barcode) from the most similar Bornean congener G. cruxniger sp. nov.

Distribution

This species is known only from Tawau, Sabah, Borneo Island, namely the Tawau Hills Park ( Figure 18 ).

Grouvellinus cruxniger Freitag, Molls and Bouma , sp. nov.

( Figures 5 , 12 (a,b), 13(a,c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (b,e)).

Type material. Holotype 3 [H1] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarters; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 13, 2♀ (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1c)M ’.

Etymology

The epithet refers to the elytral colour pattern which appears like a black cross especially in pale specimens with distinct yellowish markings.

Description

Body elongate obovate, 1.85 (males) – 1.90 (females) mm long (CL), 0.87 mm wide (EW), ca. 2.2 times as long as wide (CL/EW).

Dorsal colouration ( Figure 5 ) dominantly dark brown to black; pronotum black with gold-brown anterior margin; median transverse portion of elytra including disc dark brown to black; peripheral elytral portions with two pairs of more or less distinct, extended yellowish-brown spots; basal spots between shoulder and first row of punctures subquadrate; subapical spots between lateral margin and first row of punctures subtriangular; femora and tibiae dark brown; coxae, tarsi and antennae brown; maxillary and labial palps dark brown; pubescence shiny golden yellowish. Ventral side ( Figure 13 (b)) pale brown.

Head ( Figure 12 (a)) 0.37 – 0.39 mm wide (HW); ID 0.17 – 0.20 mm; frons and clypeus moderately densely pubescent; apical and lateral margins of labrum densely pubescent; punctures small; intervals medially flat and glabrous. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 12 (a)) ca. 0.54 mm long (PL), ca. 0.67 mm wide (PW), wider than long (PL/PW), widest posterior 0.35, narrower than elytra, anteriorly distinctly attenuate; lateral margins evenly, strongly convex, anterior margin slightly convex, anterior angles sharp, almost rectangular; pronotal disc slightly vaulted; pronotum moderately densely punctate, slightly denser at disc; punctures very small and shallowly impressed; setae moderately long; median carina absent, with indistinct pair of small posterior-median rugose patches (anterior of the scutellum); sublateral carinae indistinct and short; laterobasal and oblique impressions (the latter extending ca. posterior 0.35 – 0.60) very shallow; disc, entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; laterobasal angles and impressions rugose. Hypomeron very densely punctate.

Prosternum ( Figure 12 (b)) moderately long; lateral portions appearing rugulose, with plastron-like sense pubescence; anterior median portion clearly divided by tilt from the process, slightly rugulose to almost glabrous; prosternal process subtrapezoidal, approximately as long as wide at the base, medially spaciously impressed, rugulose, posterior margin convex, angles gently rounded.

Scutellum subcordiform, flat, with few minute punctures. Elytra ( Figure 5 ) elongate, subparallel anterior 0.1 – 0.4, moderately convex dorsally, 1.34 (males) – 1.41 (females) mm long (EL), ca. 1.6 times as long as wide (EL/EW), widest at anterior 0.6; apices broadly and almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures moderately large and moderately deeply impressed, increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices glabrous; intervals with additional, very small setiferous secondary punctures; pubescence yellowish, regularly arranged along intervals, consisting of sparse, large erected setae (frequently broken), and moderately large more or less adpressed setae; interval 8 with (genus-typical) serrate carina, interval 2 not carinate; lateral elytral margin inconspicuously serrate.

Mesoventrite ( Figure 12 (b)) with two pairs of deep grooves, one behind procoxae, another medially; the latter widely trapezoidal in males, subquadrate in females. Metaventrite ( Figure 12 (b)) with large, predominantly glabrous disc (interrupted by scattered setiferous tubercles); longitudinal impression along median suture shallow and limited to posterior two-thirds in females, over full length and deeper in males; portions adjacent to disc and coxae with irregular, deep impressions, punctures and tubercles, with distinct patch of long, yellowish setae next to mesocoxae (in both sexes); most lateral portions densely punctate and with pubescence (plastron).

Ventrite 1 ( Figure 12 (b)) with pair of longitudinal carinae between almost glabrous disc lateral portions; extended lateral portions of ventrites 1 – 2 and almost entire ventrites 3 – 5 ( Figure 12 (b)) densely covered with plastron and scattered, moderately long setae; glabrous median portion extended only up to ventrite 2; ventrite 5 with fringe of moderately long setae at lateroapical margin.

Legs ( Figure 5 ) slightly longer than body and all approximately of the same length; tibiae longer than tarsi and femora; inner (more conspicuously) and outer ventral margin of all tibiae with longitudinal patch of long trichoid setae (in both sexes); faces of femora and tibiae densely covered with short adpressed setae (plastron-like at inner femora) and some longitudinally arrange long trichoid or spine-like setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 13 (a,b)) ca. 615 μm long, ca. 180 μm wide. Phallobase slightly asymmetrical basally, reaching basal 0.5 of total aedeagus length. Median lobe ca. two times as long as wide, distinctly overreaching parameres and ventral sac, evenly conical towards the broadly round apex, apically slightly bent ventrad (lateral view). Ventral sac internally very densely covered with comparably long, thin spines that do not reach the apical opening. Parameres conical (in lateral view) almost subparallel in ventral view, apices asymmetrically rounded; with slightly more than 30 trichoid setae in apical half, most of them at the ventrolateral margin; most apical two setae longest.

Ovipositor ( Figure 13 (c)) total length ca. 730 μm; stylus ca. 36 μm long, very sligthly bent outwards with three short sensilla; coxite ca. 340 μm long with scattered extremely short, acute setae, apically slightly broadened at outer margin, with four broad hook-like setae; distal portion medially very slender, ca. 2.7 times as long as proximal portion; valvifer 390 μm long, caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Differential diagnosis

Grouvellinus cruxniger sp. nov. is similar to G. andrekuipersi and G. nigerquadratus sp. nov. especially in the yellowish elytral patterns commonly observed in pale specimens, but the borders of these patterns towards the elytral disc are more or less straight so that the remaining black elytral portions appear cross-like, with a broad transverse cross band and a slenderer sagittal band. G. cruxniger sp. nov. can be distinguished from the latter by the slightly larger size (CL 1.85 – 1.90 mm, vs. 1.7 – 1.8 mm and 1.50 – 1.75 mm, respectively), the pronotum with strongly convex lateral margins, the rectangular, acute anterior angles (vs. protruding acute, or obtuse anterior angles) and the almost conjointly rounded elytral apices. From all known Bornean Grouvellinus spp. it varies in the presence of distinct patches of long, yellowish setae at the anteriolateral metaventrite and its comparably simple aedeagus with unique combination of long phallobase (reaching ca. basal 0.5 of total aedeagus length), median lobe evenly conical and apically gently rounded, parameres conical (in lateral view) with asymmetrically rounded apices and slightly more than 30 trichoid setae in apical half.

The species varies at least by 6.3% genetic distance (654 bp CO1 barcode) from the most similar Bornean congener G. nigerquadratus sp. nov.

Distribution

This species is only known from the type locality at the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus luciaensis Freitag, Molls and Bouma , sp. nov.

( Figures 6 , 14 (a – d), 15(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Lucia River, 4° 28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, 750 m a.s.l. ( Figure 1 (f)).

Type material. Holotype 3 (SP): ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 3♀ (SP) same data as holotype; 13 [H12], 2♀ (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged wood, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6f)M ’; 3 1♀ [H22] (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged root packs, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117° 55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6h)M ’.

Etymology

The species is named in reference to its type locality, Mt. Lucia and Lucia River originating there.

Description

Body elongate obovate, males 1.91 – 1.96 mm, females 1.97 – 2.04 mm long (CL); males 0.89 – 0.91 mm, females ca. 0.96 mm wide (EW), ca. 2.1 times as long as wide (CL/EW).

Dorsal colouration ( Figure 6 ) almost entirely dark brown to black; legs paler, at least distal half of femora and claws golden brown; maxillary and labial palps dark golden brown; pubescence shiny yellowish, rather inconspicuous. Ventral side ( Figure 14 (b – d)) dark brown.

Head ( Figure 14 (a)) 0.39 – 0.43 mm wide (HW); ID 0.19 – 0.24 mm; disc of frons, clypeus, and anterior and lateral areas of labrum sparsely pubescent; clypeus with two pairs of conspicuous sublateroanterior setae and entire frontal and lateral margins of labrum densely pubescent; punctures small; intervals glabrous; except for rugulouse frontal portion bordering eyes. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 14 (a)) in males: 0.52 – 0.54 mm, in females: 0.53 – 0.57 mm long (PL); in males: 0.65 – 0.67 mm, in females: 0.66 – 0.72 mm wide (PW), wider than long (PL/PW), widest posterior 0 – 0.3, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly convex; pronotal disc moderately vaulted; entire pronotum moderately sparsely punctate; punctures small and shallowly impressed; median carina absent; with a pair of small and moderately deep posterior-median pits (anterior of the scutellum); sublateral carinae distinct and short; oblique impression moderately deep, narrow and glabrous, extending approx. anterior 0.35 – 0.65; laterobasal impression shallow, rugose; setae moderately short; interstices glabrous and flat. Hypomeron densely punctate, punctures large. Prosternum ( Figure 14 (b)) short; lateral portions with pubescence (plastron); median portion including process medially broadly impressed, slightly rugulose; prosternal process trapezoidal, slightly longer than wide, medially impressed.

Scutellum ( Figure 14 (a)) subtriangular, flat, glabrous. Elytra ( Figure 6 ) elongate, subparallel anterior 0.15 – 0.60, moderately convex dorsally, in males: 1.41 – 1.44 mm, in females: 1.44 – 1.48 mm long (EL), 1.5 – 1.6 times as long as wide (EL/EW), widest in anterior half; apices narrow, distinctly separately rounded; with eight longitudinal, distinctly impressed rows of punctures (striae); stria 8 reaching only up to 0.4 posterior; punctures somewhat regularly arranged, distinctly larger (diameter larger than interstices) and very deeply impressed in anterior and lateral portions, increasingly shallower and smaller apicad; interstices glabrous to finely rugulouse; median elytral portion, especially along interval 1 with additional very small setiferous secondary punctures; pubescence inconspicuous, consisting of very small adpressed setae and moderately large erected setae; interval 8 evenly carinate, but not serrate; interval 7 very slightly carinate; interval 5 (and intervals 2 – 4 in lesser extent) broadly elevated in subanterior portion; lateral elytral margin carinate with fine serration.

Mesoventrite ( Figure 14 (c)) with two pairs of shallow grooves behind procoxae and medially, respectively. Metaventrite ( Figure 14 (d)) moderately densely punctate, less densely at disc; longitudinal impression along entire median suture; lateral portions rather flat with inconspicuous plastron and a row of large punctures behind mesocoxae.

Ventrite 1 ( Figure 14 (d)) with pair of longitudinal carinae bordering disc; disc glabrous, sparsely punctate; lateral portions inconspicously pubescent (plastron); broad lateral portions of ventrites 1 – 4 and almost entire ventrite 5 ( Figure 14 (d)) densely covered with rather inconspicuous micro-plastron; ventrite 5 densely covered with setiferous tubercles and with apical fringe of moderately long setae.

Legs ( Figure 6 ) approximately as long as body; hindleg longest; tibia longer than tarsus and femur in all legs; proximal portion of mesofemur with loose fringe of moderately long trichoid setae at anterior-dorsal ridge (in both sexes); distal area of all tibiae with more or less densely covered with short trichoid setae; hind tibia additionally with loose longitudinal fringe of robust spine-like setae; coxae, trochanter, and particularly inner and posterior faces of femora and tibiae covered with conspicuous plastron setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 15 (a,b)) ca. 635 μm long, ca. 190 μm wide. Base reaching basal 0.38 of total aedeagus length. Median lobe ca. four times as long as wide, moderately overreaching parameres, abruptly tapering in apical third towards the slender conical, rounded apex. Ventral sac apically inflated overreaching median lobe and parameres, internally densely stippled and with dense submedian fringes of moderately long, thin spines; apically the spines get longer and reach the apical opening. Parameres apically moderately conical (in both, ventral and lateral view), usually with more than 50 trichoid setae in apical two-third, most of them at the outer ventral face; most apical two setae longest and inserted at the apex. Male sternite IX as in previous new species.

Ovipositor ( Figure 15 (c)) total length ca. 790 μm; stylus ca. 40 μm long, moderately bent outwards with three short sensilla; coxite ca. 375 μm long with scattered extremely short, acute setae and four hook-like bent sensilla, apically moderately broadened at outer margin, valvifer ca. 430 μm long, caudal portion slightly sclerotised and with very few scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with separately rounded and slightly more pointed elytral apices.

Differential diagnosis

Grouvellinus luciaensis sp. nov. can be distinguished from all known Bornean Grouvellinus spp. by its moderately large size (CL) of 1.91 – 2.04 mm (vs. ≤ 1.9 mm, or ≥ 2.3 mm), somewhat straight conical elytral posterior portion, very deeply impressed elytral striae in anterior and lateral portions, and a non-serrate 8th elytral interval. Furthermore, it is recognisable by the slight and uniform reddish-brownish tinge of the body, comparably pale femora, the aedeagal median lobe that is abruptly tapering in apical third and the comparably broad parameres with more than 50 trichoid setae in apical two-third.

The species varies by about 11 – 17% genetic distance (654 bp CO1 barcode) from the Bornean congeners.

Distribution

This species is only known from the type locality, upper Lucia River, Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus borneensis Freitag, Molls and Bouma , sp. nov.

( Figures 7 , 16 (a – c), 17(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (a,e)).

Type material. Holotype 3 [H7] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarter; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately . Paratypes: 9 3, 4♀ (SP) same data as holotype; 13, 1♀ [H49] (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1c)M ’.

Etymology

The species is named for the island of Borneo, where it is most likely endemic.

Description

Body elongate obovate, males 1.50 – 1.56 mm, females 1.60 – 1.67 mm long (CL), males 0.74 – 0.78 mm, females 0.80 – 0.83 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figure 7 ) almost entirely dark brown to black, only tarsi, antennae and maxillary palps golden brown; pubescence pale brown. Ventral side ( Figure 16 (b,c)) brown to pale brown.

Head ( Figure 16 (a,b)) in males 0.33 – 0.35 mm, in females 0.37 – 0.39 mm wide (HW); ID 0.14 – 0.17 mm; frons, clypeus, and labrum sparsely pubescent, slightly denser in lateral portions; punctures very small and scattered; intervals flat, glabrous. Frontoclypeal suture almost straight. Eyes large (eye diameter larger than ID), very slightly protruding. Antennae genus-typical.

Pronotum ( Figure 16 (a)) in males 0.44 – 0.45 mm, in females 0.46 – 0.50 mm long (PL), in males 0.52 – 0.56 mm, in females 0.59 – 0.63 mm wide (PW), wider than long (PL/PW), widest basally, narrower than elytra, anteriorly attenuate; anterior margin moderately convex; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures small and shallowly impressed; setae moderately short; median carina absent; pair of posteriormedian rugose patches distinct; sublateral carinae indistinct and short; laterobasal impression shallow, rugulose; oblique impressions shallow, partly rugulose, extending obliquely from anterior 0.2 – 0.6, then continuing aside sublateral carinae up to posterior margin; entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; disc anterior of these patches slightly rugose. Hypomeron very densely punctate.

Prosternum ( Figure 16 (c)) short; lateral portions with inconspicuous plastron pubescence; median portion including process very shallowly impressed, slightly rugulose; prosternal process subquadrate.

Scutellum ( Figure 16 (a)) subcordiform, flat, rugose, with few setiferous punctures. Elytra ( Figure 7 ) elongate, moderately convex dorsally, in males 1.07 – 1.10 mm, in females 1.22 – 1.24 mm long (EL), in males ca. 1.4 times, in females ca. 1.3 times as long as wide (EL/ EW), conspicuously widest at anterior 0.6, slightly attenuating anteriad, roundly attenuating posteriad; apices wide, almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures large and moderately deeply impressed at median disc, slightly smaller in basal portion and increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices and interval rugose; interval 8 with (genus-typical) serrate carina; interval 2 slightly carinate; all intervals with setiferous secondary punctures (inconspicuous due to rugose surface); pubescence yellowish, consisting of moderately large, erected setae and small adpressed setae; lateral elytral margin more or less distinctly serrate.

Mesoventrite ( Figure 16 (c)) with 2 pairs of subtrapezoidal grooves, median pair shallowly impressed, lateral pair (behind procoxae) deeply impressed. Metaventrite ( Figure 16 (d)) with distinct median suture over the entire length. Median disc glabrous, slightly dimorphic between sexes; lateral and marginal portions moderately densely covered with setiferous tubercles and inconspicuous plastron.

Ventrite 1 ( Figure 16 (d)) comparably short; carinae bordering glabrous disc oblique and rather inconspicuous; ventrites 1 – 2 only glabrous in most anteriomedian portion; lateral portions of ventrites 1 – 2 and entire ventrites 4 – 5 moderately densely covered with setiferous tubercles and inconspicuous plastron; apical margin of ventrite 5 fringed with pubescence.

Legs ( Figure 7 ) approximately of the same length as body; tibiae longer than tarsi and femora; trochanter, femura and tibiae almost entirely densely covered with setiferous tubercles and plastron setae except almost glabrous outer, dorsal face of tibiae and inner face of tibiae and femora. Mesofemur with loose fringe of short trichoid setae on the anterior – dorsal ridge. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 17 (a,b)) ca. 510 μm long, ca. 115 μm wide. Phallobase slightly asymmetrical basally, reaching ca. basal 0.31 of total aedeagus length. Median lobe moderately wide (ventral view), moderately overreaching parameres and ventral sac, very slightly conical in apical half, then abruptly tapered at the level of paramere tips towards slender apex; apex slightly bent ventrad (lateral view). Ventral sac internally densely stippled and with dense fringe of moderately short, thin and comparably delicate spines; few of those overreaching apical fringe. Parameres moderately shorter than median lobe and distinctly bent ventrad (lateral view), moderately broad and evenly conical from insertion to apex in lateral view, usually with more than 15 trichoid setae in apical half, most of them at the inner face; most apical setae of subequal length. Male sternite IX with median strut moderately long and almost rectangularly bent subdistally; posterior portion entirely fringed with a broad, distinctly sclerotised margin; posterior margin rounded; paraprocts subequal in length, not reaching apical margin.

Ovipositor ( Figure 17 (c)). Total length ca. 560 μm. Stylus ca. 15 μm long, very slightly bent outwards, with ca. four short sensilla. Coxite ca. 240 μm long, apically moderately broadened with scattered extremely short, acute setae and four apical sensilla. Valvifer ca. 325 μm long; caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with distinct rugulose elongate elytral patches extending from elytral basis approximately to apical 0.35 and between intervals 1 and 3 (comp. Figure 16 (a,b)). Glabrous portions of metaventral disc more extended in males and entirely very broadly impressed along median suture, while rather narrow and only slightly impressed in posterior half and subanteriorly.

Differential diagnosis

Grouvellinus borneensis sp. nov. superficially resembles G. quest in its size, proportions and entirely black colour, but can be distinguished from the latter by the rather smooth, moderately densely punctate pronotum (vs. very densely punctate), the basally smoother elytral surface with only intervals 2 and 8 partly carinate (vs. intervals 3, 5, 7 and 8 crenulate-carinate). From all known Bornean Grouvellinus spp., G. borneensis sp. nov. differs by the large eyes (eye diameter larger than ID vs. smaller than ID), the sexual dimorphism in the mediobasal elytra (but presumably also present in the still unnamed species G. sp.1.). Furthermore, it is easily recognisable by its aedeagus with median lobe slightly conical in apical half, then abruptly tapered towards the slender apex, the short aedeagal base and the long parameres with about 15 equally long setae.

The species varies by about 15 – 18% genetic distance (654 bp CO1 barcode) from the known Bornean congeners.

Distribution

This species is only known from the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus nigerquadratus Freitag, Molls and Bouma , sp. nov.

( Figures 3, 4 , 10 (a – c), 11(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (e)).

Type material. Holotype 3 [H56] (SP): ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1c)M ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 23, 1♀ [H16] (SP) same data as holotype; 2 exs. ‘ MALAYSIA: Sabah: Tawau River; rock surface, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1g)M ’; 1♀ (SP) ‘ MALAYSIA: Sabah: Tawau River; rock surface, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1f)M ’ . Other material: 13, 1♀ (SP) same data as holotype; 13 (SP) ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s. l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’.

Etymology

The epithet refers to the elytral colour pattern which appears like an oblique black square especially in pale specimens with distinct yellowish markings.

Description

Body elongate, males 1.50 – 1.55 mm, females 1.65 – 1.75 mm long (CL); males 0.74 – 0.78 mm, females 0.78 – 0.88 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figures 3, 4 ) dominantly dark brown; pronotum black, anterior margin slightly paler, golden-brown; entire median transverse portion of elytra including disc dark brown; peripheral elytral portions with two pairs of more or less distinct, extended yellowish-brown spots; basal pair between lateral margin and first row of punctures subtrapezoidal; subapical spots between lateral margin and suture obliqueoval; coxae, femora and tibiae dark brown, areas near articulations usually slightly paler; tarsi and antennae golden brown; maxillary and labial palps dark brown; pubescence yellowish. Ventral side ( Figure 10 (b,c)) dark brown.

Head ( Figure 10 (a)) 0.35 – 0.39 mm wide (HW); ID 0.16 – 0.17 mm; frons, clypeus, and labrum moderately pubescent; punctures small; intervals medially flat and glabrous, laterally rugulose. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical, usually semicircularly folded around anteriolateral eye margin.

Pronotum ( Figure 10 (a)) in males 0.48 – 0.50 mm, in females 0.48 – 0.54 mm long (PL); in males 0.57 – 0.61 mm, in females 0.61 – 0.67 mm wide (PW), wider than long (PL/PW), widest posterior 0 – 0.4, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly convex, anterior angles obtuse, rounded, slightly protruding; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures very small and shallowly impressed; setae moderately long; median carina absent; pair of short posteriomedian patches conspicuous; sublateral carinae short, rather indistinct; oblique impression moderately shallow and narrow, extending approximately anterior 0.3 – 0.7; laterobasal impression shallow; disc, entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; lateral submarginal area, laterobasal and oblique impressions rugose. Hypomeron very densely punctate.

Prosternum ( Figure 10 (b)) moderately long; lateral portions appearing rugulose, with inconspicuous pubescence (plastron); anteriomedian portion inconspicuously transversely micro-reticulate, almost glabrous; prosternal process subtrapezoidal, slightly shorter than as wide at the base, medially somewhat irregularly impressed, rugulose; posterior margin convex; angles gently rounded. Scutellum ( Figure 10 (a)) subtriangular, medially slightly impressed, glabrous.

Elytra ( Figures 3, 4 ) elongate, moderately convex dorsally. EL: males 1.05 – 1.15 mm, females 1.15 – 1.24 mm; ca. 1.45 times as long as wide (EL/EW), widest at the middle, subparallel from anterior 0.2 to 0.6, subconical towards apices; apices moderately narrow, separately rounded; with eight longitudinal, slightly impressed rows of primary punctures; primary punctures regularly arranged, large (approximately as wide as intervals) and deeply impressed anterior of clivity and in anterolateral portions, small (0.1 – 0.3 times of intervals) and shallowly impressed apicad of clivity and at most basal portion; interstices slightly rugose; intervals with additional, very inconspicuous setiferous secondary punctures; pubescence yellowish, somewhat regularly arranged along intervals, consisting of sparse, large erected setae, and moderately large adpressed setae; interval 8 with distinct, interval 7 with indistinct serrate carinae; interval 2 neither carinate nor elevated; lateral elytral margin distinctly serrate (at least in basal half).

Mesoventrite ( Figure 10 (c)) with two pairs of deep grooves, the median pair obliquely oval in males, subquadrate in females (somewhat varying in some specimens, see comments below). Metaventrite ( Figure 10 (c)) with median groove and most anterior portion somewhat glabrous; remaining disc with irregularly uneven surface and moderately densely covered with setiferous tubercles; longitudinal impression moderately deep, widely impressed, reaching ca. posterior two-thirds in males, and one-half in females; portions adjacent to disc and coxae with irregular, rugose impressions, punctures and tubercles, but without any distinct hair patch; most lateral portions densely punctate and with plastron.

Ventrite 1 ( Figure 10 (c)) with pair of longitudinal carinae; discs of ventrites 1 and 2 mainly glabrous, but with sparse regularly arranged long trichoid setae; ventrite 3 glabrous medially; lateral portions of ventrites 1 – 3 and almost entire ventrites 4 – 5 ( Figure 10 (c)) densely covered with plastron and scattered, moderately long setae; the latter more dense at apex and lateral margins of ventrite 5.

Legs ( Figures 3, 4 ) all approximately of the same length and slightly longer than body; tibiae longer than tarsi and femora; inner and outer ventral margin of all tibiae with longitudinal row or patch of long trichoid setae (in both sexes); faces of femora and tibiae very densely covered with plastron-like setae and some longitudinally arrange long trichoid or spine-like setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 11 (a,b)) ca. 590 μm long, medially ca. 105 μm wide. Base reaching basal 0.45 of total aedeagus length. Median lobe ca. 4.5 times as long as wide, moderately overreaching parameres, moderately conical towards broadly rounded apex in apical third. Ventral sac inflated ventrad, internally densely covered with long, thin spines that reach the apical opening. Parameres very slender (lateral view), laterally inflated (ventral view), apically conical, pointed (in both, ventral and lateral view), usually with slightly more than 10 trichoid setae in apical third, most of them at outer ventral face; most apical two setae longest and inserted at dorsolateral face, medioventral portion moderately densely covered with scattered very short, acute setae.

Ovipositor ( Figure 11 (c)) total length ca. 570 μm; stylus ca. 42 μm long, straight with ca. three short sensilla; coxite ca. 280 μm long, moderately densely and evenly covered with very short, acute setae; proximal portion distinctly longer than wide and distinctly overlapping with slender distal portion, apically distinctly roundly broadened at outer margin and with three or more hook-like sensilla; valvifer 295 μm long, caudal portion slightly sclerotised and with a few scattered, very short, acute setae; fibula almost straight.

Differential diagnosis

Grouvellinus nigerquadratus sp. nov. is similar to G. andrekuipersi especially in the yellowish elytral patterns commonly observed in pale specimens, but the extension of these elytral patterns is usually larger in the new species. G. nigerquadratus sp. nov. can be distinguished from G. andrekuipersi by the generally slightly smaller size (CL 1.50 – 1.75 mm vs. 1.7 – 1.8 mm), the pronotum with obtuse anterior angles (vs. protruding acute angles), the large (approximately as large as interstices) and deeply impressed elytral punctures in striae 4 and 5 anterior of clivity. From all known Bornean Grouvellinus spp. it can be distinguished by its very slender aedeagus with apically distinctly pointed and laterally inflated parameres that are covered with very short, acute setae in medioventral portions. The species varies at least by 6.3% genetic distance (654 bp CO1 barcode) from the most similar Bornean congener G. cruxniger sp. nov.

Distribution

This species is known only from Tawau, Sabah, Borneo Island, namely the Tawau Hills Park ( Figure 18 ).

Grouvellinus cruxniger Freitag, Molls and Bouma , sp. nov.

( Figures 5 , 12 (a,b), 13(a,c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (b,e)).

Type material. Holotype 3 [H1] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarters; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 13, 2♀ (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1c)M ’.

Etymology

The epithet refers to the elytral colour pattern which appears like a black cross especially in pale specimens with distinct yellowish markings.

Description

Body elongate obovate, 1.85 (males) – 1.90 (females) mm long (CL), 0.87 mm wide (EW), ca. 2.2 times as long as wide (CL/EW).

Dorsal colouration ( Figure 5 ) dominantly dark brown to black; pronotum black with gold-brown anterior margin; median transverse portion of elytra including disc dark brown to black; peripheral elytral portions with two pairs of more or less distinct, extended yellowish-brown spots; basal spots between shoulder and first row of punctures subquadrate; subapical spots between lateral margin and first row of punctures subtriangular; femora and tibiae dark brown; coxae, tarsi and antennae brown; maxillary and labial palps dark brown; pubescence shiny golden yellowish. Ventral side ( Figure 13 (b)) pale brown.

Head ( Figure 12 (a)) 0.37 – 0.39 mm wide (HW); ID 0.17 – 0.20 mm; frons and clypeus moderately densely pubescent; apical and lateral margins of labrum densely pubescent; punctures small; intervals medially flat and glabrous. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 12 (a)) ca. 0.54 mm long (PL), ca. 0.67 mm wide (PW), wider than long (PL/PW), widest posterior 0.35, narrower than elytra, anteriorly distinctly attenuate; lateral margins evenly, strongly convex, anterior margin slightly convex, anterior angles sharp, almost rectangular; pronotal disc slightly vaulted; pronotum moderately densely punctate, slightly denser at disc; punctures very small and shallowly impressed; setae moderately long; median carina absent, with indistinct pair of small posterior-median rugose patches (anterior of the scutellum); sublateral carinae indistinct and short; laterobasal and oblique impressions (the latter extending ca. posterior 0.35 – 0.60) very shallow; disc, entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; laterobasal angles and impressions rugose. Hypomeron very densely punctate.

Prosternum ( Figure 12 (b)) moderately long; lateral portions appearing rugulose, with plastron-like sense pubescence; anterior median portion clearly divided by tilt from the process, slightly rugulose to almost glabrous; prosternal process subtrapezoidal, approximately as long as wide at the base, medially spaciously impressed, rugulose, posterior margin convex, angles gently rounded.

Scutellum subcordiform, flat, with few minute punctures. Elytra ( Figure 5 ) elongate, subparallel anterior 0.1 – 0.4, moderately convex dorsally, 1.34 (males) – 1.41 (females) mm long (EL), ca. 1.6 times as long as wide (EL/EW), widest at anterior 0.6; apices broadly and almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures moderately large and moderately deeply impressed, increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices glabrous; intervals with additional, very small setiferous secondary punctures; pubescence yellowish, regularly arranged along intervals, consisting of sparse, large erected setae (frequently broken), and moderately large more or less adpressed setae; interval 8 with (genus-typical) serrate carina, interval 2 not carinate; lateral elytral margin inconspicuously serrate.

Mesoventrite ( Figure 12 (b)) with two pairs of deep grooves, one behind procoxae, another medially; the latter widely trapezoidal in males, subquadrate in females. Metaventrite ( Figure 12 (b)) with large, predominantly glabrous disc (interrupted by scattered setiferous tubercles); longitudinal impression along median suture shallow and limited to posterior two-thirds in females, over full length and deeper in males; portions adjacent to disc and coxae with irregular, deep impressions, punctures and tubercles, with distinct patch of long, yellowish setae next to mesocoxae (in both sexes); most lateral portions densely punctate and with pubescence (plastron).

Ventrite 1 ( Figure 12 (b)) with pair of longitudinal carinae between almost glabrous disc lateral portions; extended lateral portions of ventrites 1 – 2 and almost entire ventrites 3 – 5 ( Figure 12 (b)) densely covered with plastron and scattered, moderately long setae; glabrous median portion extended only up to ventrite 2; ventrite 5 with fringe of moderately long setae at lateroapical margin.

Legs ( Figure 5 ) slightly longer than body and all approximately of the same length; tibiae longer than tarsi and femora; inner (more conspicuously) and outer ventral margin of all tibiae with longitudinal patch of long trichoid setae (in both sexes); faces of femora and tibiae densely covered with short adpressed setae (plastron-like at inner femora) and some longitudinally arrange long trichoid or spine-like setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 13 (a,b)) ca. 615 μm long, ca. 180 μm wide. Phallobase slightly asymmetrical basally, reaching basal 0.5 of total aedeagus length. Median lobe ca. two times as long as wide, distinctly overreaching parameres and ventral sac, evenly conical towards the broadly round apex, apically slightly bent ventrad (lateral view). Ventral sac internally very densely covered with comparably long, thin spines that do not reach the apical opening. Parameres conical (in lateral view) almost subparallel in ventral view, apices asymmetrically rounded; with slightly more than 30 trichoid setae in apical half, most of them at the ventrolateral margin; most apical two setae longest.

Ovipositor ( Figure 13 (c)) total length ca. 730 μm; stylus ca. 36 μm long, very sligthly bent outwards with three short sensilla; coxite ca. 340 μm long with scattered extremely short, acute setae, apically slightly broadened at outer margin, with four broad hook-like setae; distal portion medially very slender, ca. 2.7 times as long as proximal portion; valvifer 390 μm long, caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Differential diagnosis

Grouvellinus cruxniger sp. nov. is similar to G. andrekuipersi and G. nigerquadratus sp. nov. especially in the yellowish elytral patterns commonly observed in pale specimens, but the borders of these patterns towards the elytral disc are more or less straight so that the remaining black elytral portions appear cross-like, with a broad transverse cross band and a slenderer sagittal band. G. cruxniger sp. nov. can be distinguished from the latter by the slightly larger size (CL 1.85 – 1.90 mm, vs. 1.7 – 1.8 mm and 1.50 – 1.75 mm, respectively), the pronotum with strongly convex lateral margins, the rectangular, acute anterior angles (vs. protruding acute, or obtuse anterior angles) and the almost conjointly rounded elytral apices. From all known Bornean Grouvellinus spp. it varies in the presence of distinct patches of long, yellowish setae at the anteriolateral metaventrite and its comparably simple aedeagus with unique combination of long phallobase (reaching ca. basal 0.5 of total aedeagus length), median lobe evenly conical and apically gently rounded, parameres conical (in lateral view) with asymmetrically rounded apices and slightly more than 30 trichoid setae in apical half.

The species varies at least by 6.3% genetic distance (654 bp CO1 barcode) from the most similar Bornean congener G. nigerquadratus sp. nov.

Distribution

This species is only known from the type locality at the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus luciaensis Freitag, Molls and Bouma , sp. nov.

( Figures 6 , 14 (a – d), 15(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Lucia River, 4° 28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, 750 m a.s.l. ( Figure 1 (f)).

Type material. Holotype 3 (SP): ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 3♀ (SP) same data as holotype; 13 [H12], 2♀ (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged wood, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6f)M ’; 3 1♀ [H22] (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged root packs, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117° 55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6h)M ’.

Etymology

The species is named in reference to its type locality, Mt. Lucia and Lucia River originating there.

Description

Body elongate obovate, males 1.91 – 1.96 mm, females 1.97 – 2.04 mm long (CL); males 0.89 – 0.91 mm, females ca. 0.96 mm wide (EW), ca. 2.1 times as long as wide (CL/EW).

Dorsal colouration ( Figure 6 ) almost entirely dark brown to black; legs paler, at least distal half of femora and claws golden brown; maxillary and labial palps dark golden brown; pubescence shiny yellowish, rather inconspicuous. Ventral side ( Figure 14 (b – d)) dark brown.

Head ( Figure 14 (a)) 0.39 – 0.43 mm wide (HW); ID 0.19 – 0.24 mm; disc of frons, clypeus, and anterior and lateral areas of labrum sparsely pubescent; clypeus with two pairs of conspicuous sublateroanterior setae and entire frontal and lateral margins of labrum densely pubescent; punctures small; intervals glabrous; except for rugulouse frontal portion bordering eyes. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 14 (a)) in males: 0.52 – 0.54 mm, in females: 0.53 – 0.57 mm long (PL); in males: 0.65 – 0.67 mm, in females: 0.66 – 0.72 mm wide (PW), wider than long (PL/PW), widest posterior 0 – 0.3, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly convex; pronotal disc moderately vaulted; entire pronotum moderately sparsely punctate; punctures small and shallowly impressed; median carina absent; with a pair of small and moderately deep posterior-median pits (anterior of the scutellum); sublateral carinae distinct and short; oblique impression moderately deep, narrow and glabrous, extending approx. anterior 0.35 – 0.65; laterobasal impression shallow, rugose; setae moderately short; interstices glabrous and flat. Hypomeron densely punctate, punctures large. Prosternum ( Figure 14 (b)) short; lateral portions with pubescence (plastron); median portion including process medially broadly impressed, slightly rugulose; prosternal process trapezoidal, slightly longer than wide, medially impressed.

Scutellum ( Figure 14 (a)) subtriangular, flat, glabrous. Elytra ( Figure 6 ) elongate, subparallel anterior 0.15 – 0.60, moderately convex dorsally, in males: 1.41 – 1.44 mm, in females: 1.44 – 1.48 mm long (EL), 1.5 – 1.6 times as long as wide (EL/EW), widest in anterior half; apices narrow, distinctly separately rounded; with eight longitudinal, distinctly impressed rows of punctures (striae); stria 8 reaching only up to 0.4 posterior; punctures somewhat regularly arranged, distinctly larger (diameter larger than interstices) and very deeply impressed in anterior and lateral portions, increasingly shallower and smaller apicad; interstices glabrous to finely rugulouse; median elytral portion, especially along interval 1 with additional very small setiferous secondary punctures; pubescence inconspicuous, consisting of very small adpressed setae and moderately large erected setae; interval 8 evenly carinate, but not serrate; interval 7 very slightly carinate; interval 5 (and intervals 2 – 4 in lesser extent) broadly elevated in subanterior portion; lateral elytral margin carinate with fine serration.

Mesoventrite ( Figure 14 (c)) with two pairs of shallow grooves behind procoxae and medially, respectively. Metaventrite ( Figure 14 (d)) moderately densely punctate, less densely at disc; longitudinal impression along entire median suture; lateral portions rather flat with inconspicuous plastron and a row of large punctures behind mesocoxae.

Ventrite 1 ( Figure 14 (d)) with pair of longitudinal carinae bordering disc; disc glabrous, sparsely punctate; lateral portions inconspicously pubescent (plastron); broad lateral portions of ventrites 1 – 4 and almost entire ventrite 5 ( Figure 14 (d)) densely covered with rather inconspicuous micro-plastron; ventrite 5 densely covered with setiferous tubercles and with apical fringe of moderately long setae.

Legs ( Figure 6 ) approximately as long as body; hindleg longest; tibia longer than tarsus and femur in all legs; proximal portion of mesofemur with loose fringe of moderately long trichoid setae at anterior-dorsal ridge (in both sexes); distal area of all tibiae with more or less densely covered with short trichoid setae; hind tibia additionally with loose longitudinal fringe of robust spine-like setae; coxae, trochanter, and particularly inner and posterior faces of femora and tibiae covered with conspicuous plastron setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 15 (a,b)) ca. 635 μm long, ca. 190 μm wide. Base reaching basal 0.38 of total aedeagus length. Median lobe ca. four times as long as wide, moderately overreaching parameres, abruptly tapering in apical third towards the slender conical, rounded apex. Ventral sac apically inflated overreaching median lobe and parameres, internally densely stippled and with dense submedian fringes of moderately long, thin spines; apically the spines get longer and reach the apical opening. Parameres apically moderately conical (in both, ventral and lateral view), usually with more than 50 trichoid setae in apical two-third, most of them at the outer ventral face; most apical two setae longest and inserted at the apex. Male sternite IX as in previous new species.

Ovipositor ( Figure 15 (c)) total length ca. 790 μm; stylus ca. 40 μm long, moderately bent outwards with three short sensilla; coxite ca. 375 μm long with scattered extremely short, acute setae and four hook-like bent sensilla, apically moderately broadened at outer margin, valvifer ca. 430 μm long, caudal portion slightly sclerotised and with very few scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with separately rounded and slightly more pointed elytral apices.

Differential diagnosis

Grouvellinus luciaensis sp. nov. can be distinguished from all known Bornean Grouvellinus spp. by its moderately large size (CL) of 1.91 – 2.04 mm (vs. ≤ 1.9 mm, or ≥ 2.3 mm), somewhat straight conical elytral posterior portion, very deeply impressed elytral striae in anterior and lateral portions, and a non-serrate 8th elytral interval. Furthermore, it is recognisable by the slight and uniform reddish-brownish tinge of the body, comparably pale femora, the aedeagal median lobe that is abruptly tapering in apical third and the comparably broad parameres with more than 50 trichoid setae in apical two-third.

The species varies by about 11 – 17% genetic distance (654 bp CO1 barcode) from the Bornean congeners.

Distribution

This species is only known from the type locality, upper Lucia River, Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus borneensis Freitag, Molls and Bouma , sp. nov.

( Figures 7 , 16 (a – c), 17(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (a,e)).

Type material. Holotype 3 [H7] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarter; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately . Paratypes: 9 3, 4♀ (SP) same data as holotype; 13, 1♀ [H49] (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1c)M ’.

Etymology

The species is named for the island of Borneo, where it is most likely endemic.

Description

Body elongate obovate, males 1.50 – 1.56 mm, females 1.60 – 1.67 mm long (CL), males 0.74 – 0.78 mm, females 0.80 – 0.83 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figure 7 ) almost entirely dark brown to black, only tarsi, antennae and maxillary palps golden brown; pubescence pale brown. Ventral side ( Figure 16 (b,c)) brown to pale brown.

Head ( Figure 16 (a,b)) in males 0.33 – 0.35 mm, in females 0.37 – 0.39 mm wide (HW); ID 0.14 – 0.17 mm; frons, clypeus, and labrum sparsely pubescent, slightly denser in lateral portions; punctures very small and scattered; intervals flat, glabrous. Frontoclypeal suture almost straight. Eyes large (eye diameter larger than ID), very slightly protruding. Antennae genus-typical.

Pronotum ( Figure 16 (a)) in males 0.44 – 0.45 mm, in females 0.46 – 0.50 mm long (PL), in males 0.52 – 0.56 mm, in females 0.59 – 0.63 mm wide (PW), wider than long (PL/PW), widest basally, narrower than elytra, anteriorly attenuate; anterior margin moderately convex; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures small and shallowly impressed; setae moderately short; median carina absent; pair of posteriormedian rugose patches distinct; sublateral carinae indistinct and short; laterobasal impression shallow, rugulose; oblique impressions shallow, partly rugulose, extending obliquely from anterior 0.2 – 0.6, then continuing aside sublateral carinae up to posterior margin; entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; disc anterior of these patches slightly rugose. Hypomeron very densely punctate.

Prosternum ( Figure 16 (c)) short; lateral portions with inconspicuous plastron pubescence; median portion including process very shallowly impressed, slightly rugulose; prosternal process subquadrate.

Scutellum ( Figure 16 (a)) subcordiform, flat, rugose, with few setiferous punctures. Elytra ( Figure 7 ) elongate, moderately convex dorsally, in males 1.07 – 1.10 mm, in females 1.22 – 1.24 mm long (EL), in males ca. 1.4 times, in females ca. 1.3 times as long as wide (EL/ EW), conspicuously widest at anterior 0.6, slightly attenuating anteriad, roundly attenuating posteriad; apices wide, almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures large and moderately deeply impressed at median disc, slightly smaller in basal portion and increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices and interval rugose; interval 8 with (genus-typical) serrate carina; interval 2 slightly carinate; all intervals with setiferous secondary punctures (inconspicuous due to rugose surface); pubescence yellowish, consisting of moderately large, erected setae and small adpressed setae; lateral elytral margin more or less distinctly serrate.

Mesoventrite ( Figure 16 (c)) with 2 pairs of subtrapezoidal grooves, median pair shallowly impressed, lateral pair (behind procoxae) deeply impressed. Metaventrite ( Figure 16 (d)) with distinct median suture over the entire length. Median disc glabrous, slightly dimorphic between sexes; lateral and marginal portions moderately densely covered with setiferous tubercles and inconspicuous plastron.

Ventrite 1 ( Figure 16 (d)) comparably short; carinae bordering glabrous disc oblique and rather inconspicuous; ventrites 1 – 2 only glabrous in most anteriomedian portion; lateral portions of ventrites 1 – 2 and entire ventrites 4 – 5 moderately densely covered with setiferous tubercles and inconspicuous plastron; apical margin of ventrite 5 fringed with pubescence.

Legs ( Figure 7 ) approximately of the same length as body; tibiae longer than tarsi and femora; trochanter, femura and tibiae almost entirely densely covered with setiferous tubercles and plastron setae except almost glabrous outer, dorsal face of tibiae and inner face of tibiae and femora. Mesofemur with loose fringe of short trichoid setae on the anterior – dorsal ridge. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 17 (a,b)) ca. 510 μm long, ca. 115 μm wide. Phallobase slightly asymmetrical basally, reaching ca. basal 0.31 of total aedeagus length. Median lobe moderately wide (ventral view), moderately overreaching parameres and ventral sac, very slightly conical in apical half, then abruptly tapered at the level of paramere tips towards slender apex; apex slightly bent ventrad (lateral view). Ventral sac internally densely stippled and with dense fringe of moderately short, thin and comparably delicate spines; few of those overreaching apical fringe. Parameres moderately shorter than median lobe and distinctly bent ventrad (lateral view), moderately broad and evenly conical from insertion to apex in lateral view, usually with more than 15 trichoid setae in apical half, most of them at the inner face; most apical setae of subequal length. Male sternite IX with median strut moderately long and almost rectangularly bent subdistally; posterior portion entirely fringed with a broad, distinctly sclerotised margin; posterior margin rounded; paraprocts subequal in length, not reaching apical margin.

Ovipositor ( Figure 17 (c)). Total length ca. 560 μm. Stylus ca. 15 μm long, very slightly bent outwards, with ca. four short sensilla. Coxite ca. 240 μm long, apically moderately broadened with scattered extremely short, acute setae and four apical sensilla. Valvifer ca. 325 μm long; caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with distinct rugulose elongate elytral patches extending from elytral basis approximately to apical 0.35 and between intervals 1 and 3 (comp. Figure 16 (a,b)). Glabrous portions of metaventral disc more extended in males and entirely very broadly impressed along median suture, while rather narrow and only slightly impressed in posterior half and subanteriorly.

Differential diagnosis

Grouvellinus borneensis sp. nov. superficially resembles G. quest in its size, proportions and entirely black colour, but can be distinguished from the latter by the rather smooth, moderately densely punctate pronotum (vs. very densely punctate), the basally smoother elytral surface with only intervals 2 and 8 partly carinate (vs. intervals 3, 5, 7 and 8 crenulate-carinate). From all known Bornean Grouvellinus spp., G. borneensis sp. nov. differs by the large eyes (eye diameter larger than ID vs. smaller than ID), the sexual dimorphism in the mediobasal elytra (but presumably also present in the still unnamed species G. sp.1.). Furthermore, it is easily recognisable by its aedeagus with median lobe slightly conical in apical half, then abruptly tapered towards the slender apex, the short aedeagal base and the long parameres with about 15 equally long setae.

The species varies by about 15 – 18% genetic distance (654 bp CO1 barcode) from the known Bornean congeners.

Distribution

This species is only known from the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus cruxniger Freitag, Molls and Bouma , sp. nov.

( Figures 5 , 12 (a,b), 13(a,c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (b,e)).

Type material. Holotype 3 [H1] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarters; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 13, 2♀ (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12. March.2018 (1c)M ’.

Etymology

The epithet refers to the elytral colour pattern which appears like a black cross especially in pale specimens with distinct yellowish markings.

Description

Body elongate obovate, 1.85 (males) – 1.90 (females) mm long (CL), 0.87 mm wide (EW), ca. 2.2 times as long as wide (CL/EW).

Dorsal colouration ( Figure 5 ) dominantly dark brown to black; pronotum black with gold-brown anterior margin; median transverse portion of elytra including disc dark brown to black; peripheral elytral portions with two pairs of more or less distinct, extended yellowish-brown spots; basal spots between shoulder and first row of punctures subquadrate; subapical spots between lateral margin and first row of punctures subtriangular; femora and tibiae dark brown; coxae, tarsi and antennae brown; maxillary and labial palps dark brown; pubescence shiny golden yellowish. Ventral side ( Figure 13 (b)) pale brown.

Head ( Figure 12 (a)) 0.37 – 0.39 mm wide (HW); ID 0.17 – 0.20 mm; frons and clypeus moderately densely pubescent; apical and lateral margins of labrum densely pubescent; punctures small; intervals medially flat and glabrous. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 12 (a)) ca. 0.54 mm long (PL), ca. 0.67 mm wide (PW), wider than long (PL/PW), widest posterior 0.35, narrower than elytra, anteriorly distinctly attenuate; lateral margins evenly, strongly convex, anterior margin slightly convex, anterior angles sharp, almost rectangular; pronotal disc slightly vaulted; pronotum moderately densely punctate, slightly denser at disc; punctures very small and shallowly impressed; setae moderately long; median carina absent, with indistinct pair of small posterior-median rugose patches (anterior of the scutellum); sublateral carinae indistinct and short; laterobasal and oblique impressions (the latter extending ca. posterior 0.35 – 0.60) very shallow; disc, entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; laterobasal angles and impressions rugose. Hypomeron very densely punctate.

Prosternum ( Figure 12 (b)) moderately long; lateral portions appearing rugulose, with plastron-like sense pubescence; anterior median portion clearly divided by tilt from the process, slightly rugulose to almost glabrous; prosternal process subtrapezoidal, approximately as long as wide at the base, medially spaciously impressed, rugulose, posterior margin convex, angles gently rounded.

Scutellum subcordiform, flat, with few minute punctures. Elytra ( Figure 5 ) elongate, subparallel anterior 0.1 – 0.4, moderately convex dorsally, 1.34 (males) – 1.41 (females) mm long (EL), ca. 1.6 times as long as wide (EL/EW), widest at anterior 0.6; apices broadly and almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures moderately large and moderately deeply impressed, increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices glabrous; intervals with additional, very small setiferous secondary punctures; pubescence yellowish, regularly arranged along intervals, consisting of sparse, large erected setae (frequently broken), and moderately large more or less adpressed setae; interval 8 with (genus-typical) serrate carina, interval 2 not carinate; lateral elytral margin inconspicuously serrate.

Mesoventrite ( Figure 12 (b)) with two pairs of deep grooves, one behind procoxae, another medially; the latter widely trapezoidal in males, subquadrate in females. Metaventrite ( Figure 12 (b)) with large, predominantly glabrous disc (interrupted by scattered setiferous tubercles); longitudinal impression along median suture shallow and limited to posterior two-thirds in females, over full length and deeper in males; portions adjacent to disc and coxae with irregular, deep impressions, punctures and tubercles, with distinct patch of long, yellowish setae next to mesocoxae (in both sexes); most lateral portions densely punctate and with pubescence (plastron).

Ventrite 1 ( Figure 12 (b)) with pair of longitudinal carinae between almost glabrous disc lateral portions; extended lateral portions of ventrites 1 – 2 and almost entire ventrites 3 – 5 ( Figure 12 (b)) densely covered with plastron and scattered, moderately long setae; glabrous median portion extended only up to ventrite 2; ventrite 5 with fringe of moderately long setae at lateroapical margin.

Legs ( Figure 5 ) slightly longer than body and all approximately of the same length; tibiae longer than tarsi and femora; inner (more conspicuously) and outer ventral margin of all tibiae with longitudinal patch of long trichoid setae (in both sexes); faces of femora and tibiae densely covered with short adpressed setae (plastron-like at inner femora) and some longitudinally arrange long trichoid or spine-like setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 13 (a,b)) ca. 615 μm long, ca. 180 μm wide. Phallobase slightly asymmetrical basally, reaching basal 0.5 of total aedeagus length. Median lobe ca. two times as long as wide, distinctly overreaching parameres and ventral sac, evenly conical towards the broadly round apex, apically slightly bent ventrad (lateral view). Ventral sac internally very densely covered with comparably long, thin spines that do not reach the apical opening. Parameres conical (in lateral view) almost subparallel in ventral view, apices asymmetrically rounded; with slightly more than 30 trichoid setae in apical half, most of them at the ventrolateral margin; most apical two setae longest.

Ovipositor ( Figure 13 (c)) total length ca. 730 μm; stylus ca. 36 μm long, very sligthly bent outwards with three short sensilla; coxite ca. 340 μm long with scattered extremely short, acute setae, apically slightly broadened at outer margin, with four broad hook-like setae; distal portion medially very slender, ca. 2.7 times as long as proximal portion; valvifer 390 μm long, caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Differential diagnosis

Grouvellinus cruxniger sp. nov. is similar to G. andrekuipersi and G. nigerquadratus sp. nov. especially in the yellowish elytral patterns commonly observed in pale specimens, but the borders of these patterns towards the elytral disc are more or less straight so that the remaining black elytral portions appear cross-like, with a broad transverse cross band and a slenderer sagittal band. G. cruxniger sp. nov. can be distinguished from the latter by the slightly larger size (CL 1.85 – 1.90 mm, vs. 1.7 – 1.8 mm and 1.50 – 1.75 mm, respectively), the pronotum with strongly convex lateral margins, the rectangular, acute anterior angles (vs. protruding acute, or obtuse anterior angles) and the almost conjointly rounded elytral apices. From all known Bornean Grouvellinus spp. it varies in the presence of distinct patches of long, yellowish setae at the anteriolateral metaventrite and its comparably simple aedeagus with unique combination of long phallobase (reaching ca. basal 0.5 of total aedeagus length), median lobe evenly conical and apically gently rounded, parameres conical (in lateral view) with asymmetrically rounded apices and slightly more than 30 trichoid setae in apical half.

The species varies at least by 6.3% genetic distance (654 bp CO1 barcode) from the most similar Bornean congener G. nigerquadratus sp. nov.

Distribution

This species is only known from the type locality at the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus luciaensis Freitag, Molls and Bouma , sp. nov.

( Figures 6 , 14 (a – d), 15(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Lucia River, 4° 28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, 750 m a.s.l. ( Figure 1 (f)).

Type material. Holotype 3 (SP): ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 3♀ (SP) same data as holotype; 13 [H12], 2♀ (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged wood, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6f)M ’; 3 1♀ [H22] (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged root packs, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117° 55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6h)M ’.

Etymology

The species is named in reference to its type locality, Mt. Lucia and Lucia River originating there.

Description

Body elongate obovate, males 1.91 – 1.96 mm, females 1.97 – 2.04 mm long (CL); males 0.89 – 0.91 mm, females ca. 0.96 mm wide (EW), ca. 2.1 times as long as wide (CL/EW).

Dorsal colouration ( Figure 6 ) almost entirely dark brown to black; legs paler, at least distal half of femora and claws golden brown; maxillary and labial palps dark golden brown; pubescence shiny yellowish, rather inconspicuous. Ventral side ( Figure 14 (b – d)) dark brown.

Head ( Figure 14 (a)) 0.39 – 0.43 mm wide (HW); ID 0.19 – 0.24 mm; disc of frons, clypeus, and anterior and lateral areas of labrum sparsely pubescent; clypeus with two pairs of conspicuous sublateroanterior setae and entire frontal and lateral margins of labrum densely pubescent; punctures small; intervals glabrous; except for rugulouse frontal portion bordering eyes. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 14 (a)) in males: 0.52 – 0.54 mm, in females: 0.53 – 0.57 mm long (PL); in males: 0.65 – 0.67 mm, in females: 0.66 – 0.72 mm wide (PW), wider than long (PL/PW), widest posterior 0 – 0.3, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly convex; pronotal disc moderately vaulted; entire pronotum moderately sparsely punctate; punctures small and shallowly impressed; median carina absent; with a pair of small and moderately deep posterior-median pits (anterior of the scutellum); sublateral carinae distinct and short; oblique impression moderately deep, narrow and glabrous, extending approx. anterior 0.35 – 0.65; laterobasal impression shallow, rugose; setae moderately short; interstices glabrous and flat. Hypomeron densely punctate, punctures large. Prosternum ( Figure 14 (b)) short; lateral portions with pubescence (plastron); median portion including process medially broadly impressed, slightly rugulose; prosternal process trapezoidal, slightly longer than wide, medially impressed.

Scutellum ( Figure 14 (a)) subtriangular, flat, glabrous. Elytra ( Figure 6 ) elongate, subparallel anterior 0.15 – 0.60, moderately convex dorsally, in males: 1.41 – 1.44 mm, in females: 1.44 – 1.48 mm long (EL), 1.5 – 1.6 times as long as wide (EL/EW), widest in anterior half; apices narrow, distinctly separately rounded; with eight longitudinal, distinctly impressed rows of punctures (striae); stria 8 reaching only up to 0.4 posterior; punctures somewhat regularly arranged, distinctly larger (diameter larger than interstices) and very deeply impressed in anterior and lateral portions, increasingly shallower and smaller apicad; interstices glabrous to finely rugulouse; median elytral portion, especially along interval 1 with additional very small setiferous secondary punctures; pubescence inconspicuous, consisting of very small adpressed setae and moderately large erected setae; interval 8 evenly carinate, but not serrate; interval 7 very slightly carinate; interval 5 (and intervals 2 – 4 in lesser extent) broadly elevated in subanterior portion; lateral elytral margin carinate with fine serration.

Mesoventrite ( Figure 14 (c)) with two pairs of shallow grooves behind procoxae and medially, respectively. Metaventrite ( Figure 14 (d)) moderately densely punctate, less densely at disc; longitudinal impression along entire median suture; lateral portions rather flat with inconspicuous plastron and a row of large punctures behind mesocoxae.

Ventrite 1 ( Figure 14 (d)) with pair of longitudinal carinae bordering disc; disc glabrous, sparsely punctate; lateral portions inconspicously pubescent (plastron); broad lateral portions of ventrites 1 – 4 and almost entire ventrite 5 ( Figure 14 (d)) densely covered with rather inconspicuous micro-plastron; ventrite 5 densely covered with setiferous tubercles and with apical fringe of moderately long setae.

Legs ( Figure 6 ) approximately as long as body; hindleg longest; tibia longer than tarsus and femur in all legs; proximal portion of mesofemur with loose fringe of moderately long trichoid setae at anterior-dorsal ridge (in both sexes); distal area of all tibiae with more or less densely covered with short trichoid setae; hind tibia additionally with loose longitudinal fringe of robust spine-like setae; coxae, trochanter, and particularly inner and posterior faces of femora and tibiae covered with conspicuous plastron setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 15 (a,b)) ca. 635 μm long, ca. 190 μm wide. Base reaching basal 0.38 of total aedeagus length. Median lobe ca. four times as long as wide, moderately overreaching parameres, abruptly tapering in apical third towards the slender conical, rounded apex. Ventral sac apically inflated overreaching median lobe and parameres, internally densely stippled and with dense submedian fringes of moderately long, thin spines; apically the spines get longer and reach the apical opening. Parameres apically moderately conical (in both, ventral and lateral view), usually with more than 50 trichoid setae in apical two-third, most of them at the outer ventral face; most apical two setae longest and inserted at the apex. Male sternite IX as in previous new species.

Ovipositor ( Figure 15 (c)) total length ca. 790 μm; stylus ca. 40 μm long, moderately bent outwards with three short sensilla; coxite ca. 375 μm long with scattered extremely short, acute setae and four hook-like bent sensilla, apically moderately broadened at outer margin, valvifer ca. 430 μm long, caudal portion slightly sclerotised and with very few scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with separately rounded and slightly more pointed elytral apices.

Differential diagnosis

Grouvellinus luciaensis sp. nov. can be distinguished from all known Bornean Grouvellinus spp. by its moderately large size (CL) of 1.91 – 2.04 mm (vs. ≤ 1.9 mm, or ≥ 2.3 mm), somewhat straight conical elytral posterior portion, very deeply impressed elytral striae in anterior and lateral portions, and a non-serrate 8th elytral interval. Furthermore, it is recognisable by the slight and uniform reddish-brownish tinge of the body, comparably pale femora, the aedeagal median lobe that is abruptly tapering in apical third and the comparably broad parameres with more than 50 trichoid setae in apical two-third.

The species varies by about 11 – 17% genetic distance (654 bp CO1 barcode) from the Bornean congeners.

Distribution

This species is only known from the type locality, upper Lucia River, Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus borneensis Freitag, Molls and Bouma , sp. nov.

( Figures 7 , 16 (a – c), 17(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (a,e)).

Type material. Holotype 3 [H7] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarter; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately . Paratypes: 9 3, 4♀ (SP) same data as holotype; 13, 1♀ [H49] (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1c)M ’.

Etymology

The species is named for the island of Borneo, where it is most likely endemic.

Description

Body elongate obovate, males 1.50 – 1.56 mm, females 1.60 – 1.67 mm long (CL), males 0.74 – 0.78 mm, females 0.80 – 0.83 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figure 7 ) almost entirely dark brown to black, only tarsi, antennae and maxillary palps golden brown; pubescence pale brown. Ventral side ( Figure 16 (b,c)) brown to pale brown.

Head ( Figure 16 (a,b)) in males 0.33 – 0.35 mm, in females 0.37 – 0.39 mm wide (HW); ID 0.14 – 0.17 mm; frons, clypeus, and labrum sparsely pubescent, slightly denser in lateral portions; punctures very small and scattered; intervals flat, glabrous. Frontoclypeal suture almost straight. Eyes large (eye diameter larger than ID), very slightly protruding. Antennae genus-typical.

Pronotum ( Figure 16 (a)) in males 0.44 – 0.45 mm, in females 0.46 – 0.50 mm long (PL), in males 0.52 – 0.56 mm, in females 0.59 – 0.63 mm wide (PW), wider than long (PL/PW), widest basally, narrower than elytra, anteriorly attenuate; anterior margin moderately convex; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures small and shallowly impressed; setae moderately short; median carina absent; pair of posteriormedian rugose patches distinct; sublateral carinae indistinct and short; laterobasal impression shallow, rugulose; oblique impressions shallow, partly rugulose, extending obliquely from anterior 0.2 – 0.6, then continuing aside sublateral carinae up to posterior margin; entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; disc anterior of these patches slightly rugose. Hypomeron very densely punctate.

Prosternum ( Figure 16 (c)) short; lateral portions with inconspicuous plastron pubescence; median portion including process very shallowly impressed, slightly rugulose; prosternal process subquadrate.

Scutellum ( Figure 16 (a)) subcordiform, flat, rugose, with few setiferous punctures. Elytra ( Figure 7 ) elongate, moderately convex dorsally, in males 1.07 – 1.10 mm, in females 1.22 – 1.24 mm long (EL), in males ca. 1.4 times, in females ca. 1.3 times as long as wide (EL/ EW), conspicuously widest at anterior 0.6, slightly attenuating anteriad, roundly attenuating posteriad; apices wide, almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures large and moderately deeply impressed at median disc, slightly smaller in basal portion and increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices and interval rugose; interval 8 with (genus-typical) serrate carina; interval 2 slightly carinate; all intervals with setiferous secondary punctures (inconspicuous due to rugose surface); pubescence yellowish, consisting of moderately large, erected setae and small adpressed setae; lateral elytral margin more or less distinctly serrate.

Mesoventrite ( Figure 16 (c)) with 2 pairs of subtrapezoidal grooves, median pair shallowly impressed, lateral pair (behind procoxae) deeply impressed. Metaventrite ( Figure 16 (d)) with distinct median suture over the entire length. Median disc glabrous, slightly dimorphic between sexes; lateral and marginal portions moderately densely covered with setiferous tubercles and inconspicuous plastron.

Ventrite 1 ( Figure 16 (d)) comparably short; carinae bordering glabrous disc oblique and rather inconspicuous; ventrites 1 – 2 only glabrous in most anteriomedian portion; lateral portions of ventrites 1 – 2 and entire ventrites 4 – 5 moderately densely covered with setiferous tubercles and inconspicuous plastron; apical margin of ventrite 5 fringed with pubescence.

Legs ( Figure 7 ) approximately of the same length as body; tibiae longer than tarsi and femora; trochanter, femura and tibiae almost entirely densely covered with setiferous tubercles and plastron setae except almost glabrous outer, dorsal face of tibiae and inner face of tibiae and femora. Mesofemur with loose fringe of short trichoid setae on the anterior – dorsal ridge. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 17 (a,b)) ca. 510 μm long, ca. 115 μm wide. Phallobase slightly asymmetrical basally, reaching ca. basal 0.31 of total aedeagus length. Median lobe moderately wide (ventral view), moderately overreaching parameres and ventral sac, very slightly conical in apical half, then abruptly tapered at the level of paramere tips towards slender apex; apex slightly bent ventrad (lateral view). Ventral sac internally densely stippled and with dense fringe of moderately short, thin and comparably delicate spines; few of those overreaching apical fringe. Parameres moderately shorter than median lobe and distinctly bent ventrad (lateral view), moderately broad and evenly conical from insertion to apex in lateral view, usually with more than 15 trichoid setae in apical half, most of them at the inner face; most apical setae of subequal length. Male sternite IX with median strut moderately long and almost rectangularly bent subdistally; posterior portion entirely fringed with a broad, distinctly sclerotised margin; posterior margin rounded; paraprocts subequal in length, not reaching apical margin.

Ovipositor ( Figure 17 (c)). Total length ca. 560 μm. Stylus ca. 15 μm long, very slightly bent outwards, with ca. four short sensilla. Coxite ca. 240 μm long, apically moderately broadened with scattered extremely short, acute setae and four apical sensilla. Valvifer ca. 325 μm long; caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with distinct rugulose elongate elytral patches extending from elytral basis approximately to apical 0.35 and between intervals 1 and 3 (comp. Figure 16 (a,b)). Glabrous portions of metaventral disc more extended in males and entirely very broadly impressed along median suture, while rather narrow and only slightly impressed in posterior half and subanteriorly.

Differential diagnosis

Grouvellinus borneensis sp. nov. superficially resembles G. quest in its size, proportions and entirely black colour, but can be distinguished from the latter by the rather smooth, moderately densely punctate pronotum (vs. very densely punctate), the basally smoother elytral surface with only intervals 2 and 8 partly carinate (vs. intervals 3, 5, 7 and 8 crenulate-carinate). From all known Bornean Grouvellinus spp., G. borneensis sp. nov. differs by the large eyes (eye diameter larger than ID vs. smaller than ID), the sexual dimorphism in the mediobasal elytra (but presumably also present in the still unnamed species G. sp.1.). Furthermore, it is easily recognisable by its aedeagus with median lobe slightly conical in apical half, then abruptly tapered towards the slender apex, the short aedeagal base and the long parameres with about 15 equally long setae.

The species varies by about 15 – 18% genetic distance (654 bp CO1 barcode) from the known Bornean congeners.

Distribution

This species is only known from the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus luciaensis Freitag, Molls and Bouma , sp. nov.

( Figures 6 , 14 (a – d), 15(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Lucia River, 4° 28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, 750 m a.s.l. ( Figure 1 (f)).

Type material. Holotype 3 (SP): ‘ MALAYSIA: Sabah: Lucia River; rock surface, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6g)M ’, terminal parts of abdomen incl. aedeagus glued separately. Paratypes: 3♀ (SP) same data as holotype; 13 [H12], 2♀ (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged wood, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117°55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6f)M ’; 3 1♀ [H22] (SP) ‘ MALAYSIA: Sabah: Lucia River; submerged root packs, run; primary forest; ca. 4°28 ʹ 34 ʹʹ N, 117° 55 ʹ 38 ʹʹ E, ca. 750 m a.s.l., leg. Taxon Expedition participants 10.March.2018 (6h)M ’.

Etymology

The species is named in reference to its type locality, Mt. Lucia and Lucia River originating there.

Description

Body elongate obovate, males 1.91 – 1.96 mm, females 1.97 – 2.04 mm long (CL); males 0.89 – 0.91 mm, females ca. 0.96 mm wide (EW), ca. 2.1 times as long as wide (CL/EW).

Dorsal colouration ( Figure 6 ) almost entirely dark brown to black; legs paler, at least distal half of femora and claws golden brown; maxillary and labial palps dark golden brown; pubescence shiny yellowish, rather inconspicuous. Ventral side ( Figure 14 (b – d)) dark brown.

Head ( Figure 14 (a)) 0.39 – 0.43 mm wide (HW); ID 0.19 – 0.24 mm; disc of frons, clypeus, and anterior and lateral areas of labrum sparsely pubescent; clypeus with two pairs of conspicuous sublateroanterior setae and entire frontal and lateral margins of labrum densely pubescent; punctures small; intervals glabrous; except for rugulouse frontal portion bordering eyes. Frontoclypeal suture straight, distinct. Eyes moderately large (eye diameter smaller than ID), slightly protruding. Antennae genus-typical.

Pronotum ( Figure 14 (a)) in males: 0.52 – 0.54 mm, in females: 0.53 – 0.57 mm long (PL); in males: 0.65 – 0.67 mm, in females: 0.66 – 0.72 mm wide (PW), wider than long (PL/PW), widest posterior 0 – 0.3, distinctly narrower than elytra, anteriorly attenuate; anterior margin slightly convex; pronotal disc moderately vaulted; entire pronotum moderately sparsely punctate; punctures small and shallowly impressed; median carina absent; with a pair of small and moderately deep posterior-median pits (anterior of the scutellum); sublateral carinae distinct and short; oblique impression moderately deep, narrow and glabrous, extending approx. anterior 0.35 – 0.65; laterobasal impression shallow, rugose; setae moderately short; interstices glabrous and flat. Hypomeron densely punctate, punctures large. Prosternum ( Figure 14 (b)) short; lateral portions with pubescence (plastron); median portion including process medially broadly impressed, slightly rugulose; prosternal process trapezoidal, slightly longer than wide, medially impressed.

Scutellum ( Figure 14 (a)) subtriangular, flat, glabrous. Elytra ( Figure 6 ) elongate, subparallel anterior 0.15 – 0.60, moderately convex dorsally, in males: 1.41 – 1.44 mm, in females: 1.44 – 1.48 mm long (EL), 1.5 – 1.6 times as long as wide (EL/EW), widest in anterior half; apices narrow, distinctly separately rounded; with eight longitudinal, distinctly impressed rows of punctures (striae); stria 8 reaching only up to 0.4 posterior; punctures somewhat regularly arranged, distinctly larger (diameter larger than interstices) and very deeply impressed in anterior and lateral portions, increasingly shallower and smaller apicad; interstices glabrous to finely rugulouse; median elytral portion, especially along interval 1 with additional very small setiferous secondary punctures; pubescence inconspicuous, consisting of very small adpressed setae and moderately large erected setae; interval 8 evenly carinate, but not serrate; interval 7 very slightly carinate; interval 5 (and intervals 2 – 4 in lesser extent) broadly elevated in subanterior portion; lateral elytral margin carinate with fine serration.

Mesoventrite ( Figure 14 (c)) with two pairs of shallow grooves behind procoxae and medially, respectively. Metaventrite ( Figure 14 (d)) moderately densely punctate, less densely at disc; longitudinal impression along entire median suture; lateral portions rather flat with inconspicuous plastron and a row of large punctures behind mesocoxae.

Ventrite 1 ( Figure 14 (d)) with pair of longitudinal carinae bordering disc; disc glabrous, sparsely punctate; lateral portions inconspicously pubescent (plastron); broad lateral portions of ventrites 1 – 4 and almost entire ventrite 5 ( Figure 14 (d)) densely covered with rather inconspicuous micro-plastron; ventrite 5 densely covered with setiferous tubercles and with apical fringe of moderately long setae.

Legs ( Figure 6 ) approximately as long as body; hindleg longest; tibia longer than tarsus and femur in all legs; proximal portion of mesofemur with loose fringe of moderately long trichoid setae at anterior-dorsal ridge (in both sexes); distal area of all tibiae with more or less densely covered with short trichoid setae; hind tibia additionally with loose longitudinal fringe of robust spine-like setae; coxae, trochanter, and particularly inner and posterior faces of femora and tibiae covered with conspicuous plastron setae. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 15 (a,b)) ca. 635 μm long, ca. 190 μm wide. Base reaching basal 0.38 of total aedeagus length. Median lobe ca. four times as long as wide, moderately overreaching parameres, abruptly tapering in apical third towards the slender conical, rounded apex. Ventral sac apically inflated overreaching median lobe and parameres, internally densely stippled and with dense submedian fringes of moderately long, thin spines; apically the spines get longer and reach the apical opening. Parameres apically moderately conical (in both, ventral and lateral view), usually with more than 50 trichoid setae in apical two-third, most of them at the outer ventral face; most apical two setae longest and inserted at the apex. Male sternite IX as in previous new species.

Ovipositor ( Figure 15 (c)) total length ca. 790 μm; stylus ca. 40 μm long, moderately bent outwards with three short sensilla; coxite ca. 375 μm long with scattered extremely short, acute setae and four hook-like bent sensilla, apically moderately broadened at outer margin, valvifer ca. 430 μm long, caudal portion slightly sclerotised and with very few scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with separately rounded and slightly more pointed elytral apices.

Differential diagnosis

Grouvellinus luciaensis sp. nov. can be distinguished from all known Bornean Grouvellinus spp. by its moderately large size (CL) of 1.91 – 2.04 mm (vs. ≤ 1.9 mm, or ≥ 2.3 mm), somewhat straight conical elytral posterior portion, very deeply impressed elytral striae in anterior and lateral portions, and a non-serrate 8th elytral interval. Furthermore, it is recognisable by the slight and uniform reddish-brownish tinge of the body, comparably pale femora, the aedeagal median lobe that is abruptly tapering in apical third and the comparably broad parameres with more than 50 trichoid setae in apical two-third.

The species varies by about 11 – 17% genetic distance (654 bp CO1 barcode) from the Bornean congeners.

Distribution

This species is only known from the type locality, upper Lucia River, Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus borneensis Freitag, Molls and Bouma , sp. nov.

( Figures 7 , 16 (a – c), 17(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (a,e)).

Type material. Holotype 3 [H7] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarter; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately . Paratypes: 9 3, 4♀ (SP) same data as holotype; 13, 1♀ [H49] (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1c)M ’.

Etymology

The species is named for the island of Borneo, where it is most likely endemic.

Description

Body elongate obovate, males 1.50 – 1.56 mm, females 1.60 – 1.67 mm long (CL), males 0.74 – 0.78 mm, females 0.80 – 0.83 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figure 7 ) almost entirely dark brown to black, only tarsi, antennae and maxillary palps golden brown; pubescence pale brown. Ventral side ( Figure 16 (b,c)) brown to pale brown.

Head ( Figure 16 (a,b)) in males 0.33 – 0.35 mm, in females 0.37 – 0.39 mm wide (HW); ID 0.14 – 0.17 mm; frons, clypeus, and labrum sparsely pubescent, slightly denser in lateral portions; punctures very small and scattered; intervals flat, glabrous. Frontoclypeal suture almost straight. Eyes large (eye diameter larger than ID), very slightly protruding. Antennae genus-typical.

Pronotum ( Figure 16 (a)) in males 0.44 – 0.45 mm, in females 0.46 – 0.50 mm long (PL), in males 0.52 – 0.56 mm, in females 0.59 – 0.63 mm wide (PW), wider than long (PL/PW), widest basally, narrower than elytra, anteriorly attenuate; anterior margin moderately convex; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures small and shallowly impressed; setae moderately short; median carina absent; pair of posteriormedian rugose patches distinct; sublateral carinae indistinct and short; laterobasal impression shallow, rugulose; oblique impressions shallow, partly rugulose, extending obliquely from anterior 0.2 – 0.6, then continuing aside sublateral carinae up to posterior margin; entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; disc anterior of these patches slightly rugose. Hypomeron very densely punctate.

Prosternum ( Figure 16 (c)) short; lateral portions with inconspicuous plastron pubescence; median portion including process very shallowly impressed, slightly rugulose; prosternal process subquadrate.

Scutellum ( Figure 16 (a)) subcordiform, flat, rugose, with few setiferous punctures. Elytra ( Figure 7 ) elongate, moderately convex dorsally, in males 1.07 – 1.10 mm, in females 1.22 – 1.24 mm long (EL), in males ca. 1.4 times, in females ca. 1.3 times as long as wide (EL/ EW), conspicuously widest at anterior 0.6, slightly attenuating anteriad, roundly attenuating posteriad; apices wide, almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures large and moderately deeply impressed at median disc, slightly smaller in basal portion and increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices and interval rugose; interval 8 with (genus-typical) serrate carina; interval 2 slightly carinate; all intervals with setiferous secondary punctures (inconspicuous due to rugose surface); pubescence yellowish, consisting of moderately large, erected setae and small adpressed setae; lateral elytral margin more or less distinctly serrate.

Mesoventrite ( Figure 16 (c)) with 2 pairs of subtrapezoidal grooves, median pair shallowly impressed, lateral pair (behind procoxae) deeply impressed. Metaventrite ( Figure 16 (d)) with distinct median suture over the entire length. Median disc glabrous, slightly dimorphic between sexes; lateral and marginal portions moderately densely covered with setiferous tubercles and inconspicuous plastron.

Ventrite 1 ( Figure 16 (d)) comparably short; carinae bordering glabrous disc oblique and rather inconspicuous; ventrites 1 – 2 only glabrous in most anteriomedian portion; lateral portions of ventrites 1 – 2 and entire ventrites 4 – 5 moderately densely covered with setiferous tubercles and inconspicuous plastron; apical margin of ventrite 5 fringed with pubescence.

Legs ( Figure 7 ) approximately of the same length as body; tibiae longer than tarsi and femora; trochanter, femura and tibiae almost entirely densely covered with setiferous tubercles and plastron setae except almost glabrous outer, dorsal face of tibiae and inner face of tibiae and femora. Mesofemur with loose fringe of short trichoid setae on the anterior – dorsal ridge. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 17 (a,b)) ca. 510 μm long, ca. 115 μm wide. Phallobase slightly asymmetrical basally, reaching ca. basal 0.31 of total aedeagus length. Median lobe moderately wide (ventral view), moderately overreaching parameres and ventral sac, very slightly conical in apical half, then abruptly tapered at the level of paramere tips towards slender apex; apex slightly bent ventrad (lateral view). Ventral sac internally densely stippled and with dense fringe of moderately short, thin and comparably delicate spines; few of those overreaching apical fringe. Parameres moderately shorter than median lobe and distinctly bent ventrad (lateral view), moderately broad and evenly conical from insertion to apex in lateral view, usually with more than 15 trichoid setae in apical half, most of them at the inner face; most apical setae of subequal length. Male sternite IX with median strut moderately long and almost rectangularly bent subdistally; posterior portion entirely fringed with a broad, distinctly sclerotised margin; posterior margin rounded; paraprocts subequal in length, not reaching apical margin.

Ovipositor ( Figure 17 (c)). Total length ca. 560 μm. Stylus ca. 15 μm long, very slightly bent outwards, with ca. four short sensilla. Coxite ca. 240 μm long, apically moderately broadened with scattered extremely short, acute setae and four apical sensilla. Valvifer ca. 325 μm long; caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with distinct rugulose elongate elytral patches extending from elytral basis approximately to apical 0.35 and between intervals 1 and 3 (comp. Figure 16 (a,b)). Glabrous portions of metaventral disc more extended in males and entirely very broadly impressed along median suture, while rather narrow and only slightly impressed in posterior half and subanteriorly.

Differential diagnosis

Grouvellinus borneensis sp. nov. superficially resembles G. quest in its size, proportions and entirely black colour, but can be distinguished from the latter by the rather smooth, moderately densely punctate pronotum (vs. very densely punctate), the basally smoother elytral surface with only intervals 2 and 8 partly carinate (vs. intervals 3, 5, 7 and 8 crenulate-carinate). From all known Bornean Grouvellinus spp., G. borneensis sp. nov. differs by the large eyes (eye diameter larger than ID vs. smaller than ID), the sexual dimorphism in the mediobasal elytra (but presumably also present in the still unnamed species G. sp.1.). Furthermore, it is easily recognisable by its aedeagus with median lobe slightly conical in apical half, then abruptly tapered towards the slender apex, the short aedeagal base and the long parameres with about 15 equally long setae.

The species varies by about 15 – 18% genetic distance (654 bp CO1 barcode) from the known Bornean congeners.

Distribution

This species is only known from the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Grouvellinus borneensis Freitag, Molls and Bouma , sp. nov.

( Figures 7 , 16 (a – c), 17(a – c))

Type locality. Malaysia, Sabah (on Borneo Island), Tawau Hills Park, Tawau River, 4° 24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l. ( Figure 1 (a,e)).

Type material. Holotype 3 [H7] (SP): ‘ MALAYSIA: Sabah: Tawau River; Light trap near Park Headquarter; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 270 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1)L ’, terminal parts of abdomen incl. aedeagus glued separately . Paratypes: 9 3, 4♀ (SP) same data as holotype; 13, 1♀ [H49] (SP) ‘ MALAYSIA: Sabah: Tawau River; bottom gravel, run; primary forest; ca. 4°24 ʹ 14 ʹʹ N, 117°53 ʹ 35 ʹʹ E, 280 m a.s.l.; leg. Taxon Expedition participants 12.March.2018 (1c)M ’.

Etymology

The species is named for the island of Borneo, where it is most likely endemic.

Description

Body elongate obovate, males 1.50 – 1.56 mm, females 1.60 – 1.67 mm long (CL), males 0.74 – 0.78 mm, females 0.80 – 0.83 mm wide (EW), 2.0 times as long as wide (CL/EW).

Dorsal colouration ( Figure 7 ) almost entirely dark brown to black, only tarsi, antennae and maxillary palps golden brown; pubescence pale brown. Ventral side ( Figure 16 (b,c)) brown to pale brown.

Head ( Figure 16 (a,b)) in males 0.33 – 0.35 mm, in females 0.37 – 0.39 mm wide (HW); ID 0.14 – 0.17 mm; frons, clypeus, and labrum sparsely pubescent, slightly denser in lateral portions; punctures very small and scattered; intervals flat, glabrous. Frontoclypeal suture almost straight. Eyes large (eye diameter larger than ID), very slightly protruding. Antennae genus-typical.

Pronotum ( Figure 16 (a)) in males 0.44 – 0.45 mm, in females 0.46 – 0.50 mm long (PL), in males 0.52 – 0.56 mm, in females 0.59 – 0.63 mm wide (PW), wider than long (PL/PW), widest basally, narrower than elytra, anteriorly attenuate; anterior margin moderately convex; pronotal disc slightly vaulted; entire pronotum moderately densely punctate; punctures small and shallowly impressed; setae moderately short; median carina absent; pair of posteriormedian rugose patches distinct; sublateral carinae indistinct and short; laterobasal impression shallow, rugulose; oblique impressions shallow, partly rugulose, extending obliquely from anterior 0.2 – 0.6, then continuing aside sublateral carinae up to posterior margin; entire anterior portion and portion between sublateral carinae and posterior-median patches glabrous; disc anterior of these patches slightly rugose. Hypomeron very densely punctate.

Prosternum ( Figure 16 (c)) short; lateral portions with inconspicuous plastron pubescence; median portion including process very shallowly impressed, slightly rugulose; prosternal process subquadrate.

Scutellum ( Figure 16 (a)) subcordiform, flat, rugose, with few setiferous punctures. Elytra ( Figure 7 ) elongate, moderately convex dorsally, in males 1.07 – 1.10 mm, in females 1.22 – 1.24 mm long (EL), in males ca. 1.4 times, in females ca. 1.3 times as long as wide (EL/ EW), conspicuously widest at anterior 0.6, slightly attenuating anteriad, roundly attenuating posteriad; apices wide, almost conjointly rounded; with eight longitudinal, slightly impressed rows of primary punctures (striae); primary punctures large and moderately deeply impressed at median disc, slightly smaller in basal portion and increasingly smaller and more shallowly impressed apicad, regularly arranged in median rows, less regularly arranged in lateral rows; interstices and interval rugose; interval 8 with (genus-typical) serrate carina; interval 2 slightly carinate; all intervals with setiferous secondary punctures (inconspicuous due to rugose surface); pubescence yellowish, consisting of moderately large, erected setae and small adpressed setae; lateral elytral margin more or less distinctly serrate.

Mesoventrite ( Figure 16 (c)) with 2 pairs of subtrapezoidal grooves, median pair shallowly impressed, lateral pair (behind procoxae) deeply impressed. Metaventrite ( Figure 16 (d)) with distinct median suture over the entire length. Median disc glabrous, slightly dimorphic between sexes; lateral and marginal portions moderately densely covered with setiferous tubercles and inconspicuous plastron.

Ventrite 1 ( Figure 16 (d)) comparably short; carinae bordering glabrous disc oblique and rather inconspicuous; ventrites 1 – 2 only glabrous in most anteriomedian portion; lateral portions of ventrites 1 – 2 and entire ventrites 4 – 5 moderately densely covered with setiferous tubercles and inconspicuous plastron; apical margin of ventrite 5 fringed with pubescence.

Legs ( Figure 7 ) approximately of the same length as body; tibiae longer than tarsi and femora; trochanter, femura and tibiae almost entirely densely covered with setiferous tubercles and plastron setae except almost glabrous outer, dorsal face of tibiae and inner face of tibiae and femora. Mesofemur with loose fringe of short trichoid setae on the anterior – dorsal ridge. Legs not conspicuously varying between sexes.

Aedeagus ( Figure 17 (a,b)) ca. 510 μm long, ca. 115 μm wide. Phallobase slightly asymmetrical basally, reaching ca. basal 0.31 of total aedeagus length. Median lobe moderately wide (ventral view), moderately overreaching parameres and ventral sac, very slightly conical in apical half, then abruptly tapered at the level of paramere tips towards slender apex; apex slightly bent ventrad (lateral view). Ventral sac internally densely stippled and with dense fringe of moderately short, thin and comparably delicate spines; few of those overreaching apical fringe. Parameres moderately shorter than median lobe and distinctly bent ventrad (lateral view), moderately broad and evenly conical from insertion to apex in lateral view, usually with more than 15 trichoid setae in apical half, most of them at the inner face; most apical setae of subequal length. Male sternite IX with median strut moderately long and almost rectangularly bent subdistally; posterior portion entirely fringed with a broad, distinctly sclerotised margin; posterior margin rounded; paraprocts subequal in length, not reaching apical margin.

Ovipositor ( Figure 17 (c)). Total length ca. 560 μm. Stylus ca. 15 μm long, very slightly bent outwards, with ca. four short sensilla. Coxite ca. 240 μm long, apically moderately broadened with scattered extremely short, acute setae and four apical sensilla. Valvifer ca. 325 μm long; caudal portion slightly sclerotised and with scattered, extremely short, acute setae; fibula almost straight.

Sexual dimorphism

Females with distinct rugulose elongate elytral patches extending from elytral basis approximately to apical 0.35 and between intervals 1 and 3 (comp. Figure 16 (a,b)). Glabrous portions of metaventral disc more extended in males and entirely very broadly impressed along median suture, while rather narrow and only slightly impressed in posterior half and subanteriorly.

Differential diagnosis

Grouvellinus borneensis sp. nov. superficially resembles G. quest in its size, proportions and entirely black colour, but can be distinguished from the latter by the rather smooth, moderately densely punctate pronotum (vs. very densely punctate), the basally smoother elytral surface with only intervals 2 and 8 partly carinate (vs. intervals 3, 5, 7 and 8 crenulate-carinate). From all known Bornean Grouvellinus spp., G. borneensis sp. nov. differs by the large eyes (eye diameter larger than ID vs. smaller than ID), the sexual dimorphism in the mediobasal elytra (but presumably also present in the still unnamed species G. sp.1.). Furthermore, it is easily recognisable by its aedeagus with median lobe slightly conical in apical half, then abruptly tapered towards the slender apex, the short aedeagal base and the long parameres with about 15 equally long setae.

The species varies by about 15 – 18% genetic distance (654 bp CO1 barcode) from the known Bornean congeners.

Distribution

This species is only known from the Tawau Hills Park, Sabah, Borneo Island ( Figure 18 ).

Figures

Figure 1. (a) Co-authors and assistants of the Taxon Expedition to Tawau Hills Park, Sabah, Malaysian Borneo, performing microhabitat-specific sampling; (b) Co-authors during beetle collection at a blacklight trap installed in the vicinity of the Tawau River; (c) The first author (second from the right) instructing Taxon Expedition participants on the identification of riffle beetles; (d) the transportable molecular field laboratory at the Tawau Park Station; (e) Type locality of Grouvellinus borneensis, sp. nov., G. cruxniger, sp. nov., G. nigerquadratus, sp. nov., and collection site of G. sp. 1; (f) Type locality of Grouvellinus luciaensis, sp. nov., and collection site of G. andrekuipersi, G. nigerquadratus, sp. nov. and G. sp. 2.

Figure 10. Grouvellinus nigerquadratus, sp. nov. (paratypes): (a) anteriodorsal aspect with pronotum; (b) anterioventral aspect with prosternum; (c) posterioventral aspect with meso-, metaventrite, and ventrites 1–5.

Figure 11. Grouvellinus nigerquadratus, sp. nov. (paratypes): (a) aedeagus, lateral; (b) aedeagus, ventral; (c) ovipositor (half), ventral. Scale bar = 0.1 mm.

Figure 12. Grouvellinus cruxniger, sp. nov. (paratypes): (a) anteriodorsal aspect with pronotum and elytra; (b) ventral aspect with prosternum, meso-, metaventrite, and ventrites 1–5.

Figure 13. Grouvellinus cruxniger, sp. nov. (paratypes): (a) aedeagus, lateral; (b) aedeagus, ventral; (c) ovipositor (half), ventral. Scale bar = 0.1 mm.

Figure 14. Grouvellinus luciaensis, sp. nov. (paratypes): (a) anteriodorsal aspect with pronotum; (b) anterioventral aspect with head and prosternum; (c) ventral aspect with prosternum and mesoventrite, (d) posterioventral aspect with metaventrite and ventrites 1–5.

Figure 15. Grouvellinus luciaensis, sp. nov. (paratypes): (a) aedeagus, lateral; (b) aedeagus, ventral; (c) ovipositor (half), ventral. Scale bar = 0.1 mm.

Figure 16. Grouvellinus borneensis, sp. nov. (paratypes): (a) anteriodorsal aspect with pronotum and elytra; (b) ventral aspect with prosternum and mesoventrite; (c) posteriodorsal aspect with metaventrite and ventrites 1–5.

Figure 17. Grouvellinus borneensis, sp. nov. (paratypes): (a) aedeagus, lateral; (b) aedeagus, ventral; (c) ovipositor (half), ventral. Scale bar = 0.1 mm.

Figure 18. Map of Sabah and Brunei (Borneo) with collecting site of Grouvellinus species with new species record in red fonts.

Figures 2–5. Habitus of the Grouvellinus species collected from the Tawan Hills Park. 2: G. andrekuipersi; 3: G. nigerquadratus, sp. nov. (paratype male from Tawau River); 4: G. nigerquadratus, sp. nov. (male from Lucia River); 5: G.cruxniger, sp. nov. (paratype male from Lucia River). Scale: 1 mm.

Figures 6–9. Habitus of the Grouvellinus species collected from the Tawan Hills Park. 6: G. luciaensis, sp. nov. (paratype male from Lucia River); 7: G. borneensis, sp. nov. (paratype male from Tawau River environment); 8: G. sp.1 (female from Tawau River environment); 9: G. sp.2 (female from Lucia River). Scale: 1 mm.