Holotype : male (IZFB) labeled as follows: „WESTERN SERBIA: town of Bajina Bašta, Mt. Tara, village of Solotuša, an unnamed cave, 43°53'46.023"N, 19°36'1.339"E, 20.V–5.XI.2017, pitfall traps, MK“ (white label, printed) / „Holotypus Duvalius (Biharotrechus) semecensis tarensis ssp. nov. Ćurčić & Vesović det. 2021“ (red label, printed) (Fig. 2).

Figure 2. 

Duvalius (Biharotrechus) semecensis tarensis ssp. nov. from an unnamed cave, village of Solotuša, near the town of Bajina Bašta, Mt. Tara, western Serbia. HT male, habitus, dorsal aspect. Scale bar: 2 mm.

Paratypes (12 specimens). The same data as for HT [seven females, IZFB]; the same data as for HT except for date and collector [two females, IZFB, September, 17, 2013, FB]; one male and one female (IZFB) labeled as follows: „WESTERN SERBIA: town of Bajina Bašta, Mt. Tara, village of Kaluđerske Bare, pit 4-1-3-27, 43°54'30.712"N, 19°33'11.585"E, 20.V–5.XI.2017, pitfall traps, MK“; the same data as for the two preceding PTs except for date and collector [one female, IZFB, July, 5, 2014, FB]. All PTs are labeled with white, printed locality labels and with red printed labels „Paratypus Duvalius (Biharotrechus) semecensis tarensis ssp. nov. Ćurčić & Vesović det. 2021“.

The new subspecies is named after its terra typica – Mt. Tara in western Serbia.

A medium-sized (TL 4.31–4.67 mm, L 4.83–5.18 mm), glabrous, depigmented trechine beetle with the morphological character states of the subgenus Biharotrechus, genus Duvalius (see the Discussion). Colour reddish-brown, head relatively large, rounded, with deep, complete frontal furrows and vestigial eyes. Pronotum transverse, heart-shaped, elytra sub-oval, with two pairs of discal setae (Figs 2, 3).

Figures 3–8. 

Duvalius (Biharotrechus) semecensis tarensis ssp. nov. from Mt. Tara, near the town of Bajina Bašta, western Serbia 3 HT male, head, lateral aspect 4 HT male, aedeagus, lateral aspect 5 HT male, aedeagus, dorsal aspect 6 HT male, copulatory piece, dorsal aspect 7 HT male, abdominal sternite IX (urite) 8 PT female, genitalia, dorsal aspect. Scale bars: 0.5 mm (3); 0.2 mm (4, 5, 7, 8); 0.1 mm (6).

Duvalius (Biharotrechus) semecensis tarensis ssp. nov. is most closely related to the nominotypic subspecies of Duvalius (Biharotrechus) semecensis Winkler, 1926 from eastern Bosnia and Herzegovina (cave- and MSS-dwelling, from Mt. Sjemeć, near the town of Višegrad), Duvalius (Biharotrechus) reufi Pavićević & Popović, 2003 from southwestern Serbia (cave-dwelling, from the Pešter Plateau and Mt. Javor, near the towns of Sjenica and Nova Varoš), as well to the following three Duvalius species distributed in western and southwestern Serbia: Duvalius (Duvalius) suvoborensis Pavićević & Popović, 2001 (cave-dwelling, from Mt. Suvobor, near the town of Valjevo), D. (D.) javorensis (S. Ćurčić, Brajković & B. Ćurčić, 2003) (cave-dwelling, from Mt. Javor, near the town of Nova Varoš) and D. (D.) suvodolensis (S. Ćurčić, Brajković & B. Ćurčić, 2003) (MSS-dwelling, from Mt. Javor, near the town of Nova Varoš) (Figs 9, 10, 14, 16, 18, 19) (Winkler 1926; Jeannel 1928; Pavićević and Popović 2001, 2003; Ćurčić et al. 2003a, 2003b). All the listed taxa share the following morpho-anatomical features: they possess vestigial eyes, sharp hind pronotal angles and a specific unifid gutter-formed copulatory piece. In D. (B.) semecensis tarensis ssp. nov. elytral base is somewhat oblique and shoulders are sloped and rounded, in D. (B.) semecensis semecensis Winkler, 1926 elytral base is strongly oblique and shoulders are sloped and obtuse, while in the remaining four species elytral base is almost straight and shoulders are elevated and rounded. Other differences between the new subspecies and its most related congeners are listed below.

Figure 9. 

A map of Serbia with sites where Biharotrechus (in lime green colour) and Duvalius s. str. taxa (in pink colour) were recorded circle D. (D.) suvoborensis ellipse D. (D.) suvodolensis hexagon D. (B.) reufi pentagon D. (D.) javorensis rhombus D. (D.) sturanyi sturanyi star D. (D.) leonhardi matejkai sun D. (D.) bolei triangle D. (B.) semecensis tarensis ssp. nov. AL Albania BA Bosnia and Herzegovina BG Bulgaria HR Croatia HU Hungary ME Montenegro MK North Macedonia RO Romania.

From the HT of D. (B.) semecensis semecensis it is differed by the TL (4.17 mm vs. 4.31–4.67 mm), length and ratio of length to width of certain antennomeres (antennomere 11 longest, followed by antennomeres 1 and 3, A2L/A2W 1.89, A10L/A10W 2.60 vs. antennomere 3 longest, followed by antennomere 11, A2L/A2W 2.40, A10L/A10W 2.67–2.72), shape of eyes (oval vs. lenticular), number of ommatidia (1–2 vs. 5–8), position of maximum width of pronotum (slightly before anterior third vs. at anterior fourth), shape of lateral pronotal margins before hind pronotal angles (more sinuated vs. less sinuated), shape of lateral pronotal furrows (relatively narrow and shallow vs. wide and deep), position of anterolateral pair of pronotal setae (slightly before anterior third of pronotal length vs. in anterior fifth of pronotal length), shape and ratio of length to width of elytra (more elongate, sub-ovate, EL/EW 1.65 vs. less elongate, sub-oval, EL/EW 1.51–1.60), position of maximum width of elytra (slightly after middle vs. at middle), position of the first pair of elytral discal setae (slightly before level of third humeral seta vs. slightly below level of second humeral seta), position of the second pair of elytral discal setae (after middle vs. at middle or slightly above), shape of median lobe (thinner, more curved, apex more acute in lateral view vs. wider, less curved, apex less acute in lateral view) and basal bulb of aedeagus (moderately elongate, somewhat narrowed distally in lateral view vs. large, rounded) and shape of copulatory piece (edges largely folded dorsally to form a deep cone, without any projection vs. in form of a shallow gutter, with a longitudinal sclerotized projection, edges not folded and sclerotized) (Table 1, Figs 10, 11) (Winkler 1926; Jeannel 1928).

Figures 10–13. 

Duvalius (Biharotrechus) semecensis semecensis from the Vrteljka Cave, village of Đipi, near the town of Višegrad, Mt. Sjemeć, eastern Bosnia and Herzegovina 10 HT male, habitus, dorsal aspect 11 HT male, head, lateral aspect 12 locality data label of HT male 13 taxonomic name label of HT male. Scale bars: 2 mm (10); 0.5 mm (11).

From D. (B.) reufi, D. (B.) semecensis tarensis ssp. nov. is differed by the body shape (more elongate vs. less elongate), HL/HW (head somewhat longer than wide vs. head wider than long), number of ommatidia (none vs. 5–8), width of genae (wider vs. narrower), antennal length (extending the middle of elytra or longer vs. not reaching the middle of elytra), shape of pronotum (more transverse vs. less transverse), position of maximum width of pronotum (at anterior third vs. at anterior fourth), shape of elytra (sub-parallel vs. sub-oval), shape of the median lobe (more curved, straight in distal half, with rounded apex in lateral view and narrowing distally in dorsal view vs. less curved, curved in distal half, with pointed apex in lateral view and sub-parallel in dorsal view) and basal bulb of aedeagus (elongate, narrowed distally in lateral view vs. large, rounded) and shape of copulatory piece (elongate, narrowed distally, without any projection, deeply incised proximally vs. wide, rounded distally, with a longitudinal sclerotized projection, shallowly incised proximally) (Fig. 14) (Pavićević and Popović 2003).

Figures 14–19. 

Habitus (dorsal aspect) of the taxa of Biharotrechus and Duvalius s. str. from Serbia 14 D. (B.) reufi 15 D. (D.) bolei 16 D. (D.) javorensis 17 D. (D.) sturanyi sturanyi 18 D. (D.) suvoborensis 19 D. (D.) suvodolensis. Scale bars: 1 mm.

From D. (D.) suvoborensis, D. (B.) semecensis tarensis ssp. nov. is differed by the body shape (more elongate vs. less elongate), HL/HW (head somewhat longer than wide vs. head wider than long), number of ommatidia (about 10 vs. 5–8), antennal length (extending the middle of elytra or longer vs. not reaching the middle of elytra), shape of lateral pronotal margins at largest pronotal width (obtusely rounded vs. regularly rounded), shape of hind pronotal angles (less sharp vs. sharper), shape of the median lobe of aedeagus (apex less distally sub-apically elevated in lateral view vs. apex more distally sub-apically elevated in lateral view) and shape of copulatory piece (sub-parallel, with an obtuse apex, a deeper gutter and without any projection, not incised proximally vs. apically narrowed, with a rounded apex, a shallower gutter and a longitudinal sclerotized projection, shallowly incised proximally) (Fig. 18) (Pavićević and Popović 2001).

From D. (D.) javorensis, the new subspecies is differed by the head size in relation to the body (more voluminous vs. less voluminous), width of genae (wider vs. narrower), antennal length (extending over the middle of elytra vs. not reaching the middle of elytra), number of ommatidia (10–14 vs. 5–8), position of maximum width of pronotum (at anterior third vs. at anterior fourth) and elytra (below middle vs. at middle), shape of the median lobe of aedeagus (more robust, not narrowing apically, apex obtuse in dorsal view vs. less robust, narrowing apically, apex rounded in dorsal view) and shape of copulatory piece (sub-parallel, with an obtuse apex, a deeper gutter and without any projection vs. apically narrowed, with a rounded apex, a shallower gutter and a longitudinal sclerotized projection) (Fig. 16) (Ćurčić et al. 2003b).

From D. (D.) suvodolensis, D. (B.) semecensis tarensis ssp. nov. is differed by the HL/HW (head somewhat longer than wide vs. head wider than long), number of ommatidia (about 17 vs. 5–8), shape of lateral elytral margins (arcuate, sub-parallel vs. rounded) and position of maximum width of elytra (below middle vs. at middle) (Fig. 19) (Ćurčić et al. 2003a).

Medium-sized. TL 4.31–4.67 mm (HT 4.51 mm), L 4.83–5.18 mm.

Habitus : Body elongate. Colour reddish-brown. Legs and palpi paler.

Integument : Smooth, lustrous, both head and pronotum with a distinct isodiametric microsculpture, while microsculpture of elytra with both isodiametric and transverse meshes.

Head : Relatively large, around as long as 1/6 of TL, rounded (Fig. 2), distinctly narrower than pronotum, glabrous. Genae rounded. Neck well-developed. HL 0.70–0.75 mm (HT 0.72 mm), HW 0.80–0.87 mm (HT 0.82 mm), HL/HW 0.85–0.88 (HT 0.87). Frontal furrows complete, deep, reaching neck constriction. Two pairs of supraorbital setae present, anterior pair situated at level of reduced eyes, posterior pair near frontal furrows. Mandibles relatively long and thin, sharply pointed, right one with a retinaculum. Labrum emarginate, with three pairs of setae. Clypeus with two pairs of setae. Eyes are strongly reduced, lenticular, whitish, darkly bordered (Fig. 3), composed of a few (5–8) ommatidia. Antennae are long and slender, densely pubescent, reaching almost half of elytral length when stretched backward. Antennomere 3 longest, followed by antennomere 11, antennomere 2 shortest (A2L/A2W 2.40), scape and antennomeres 4–10 nearly equally long, A10L/A10W 2.67–2.72.

Thorax : Pronotum glabrous, transverse, cordiform (Fig. 2), slightly wider than long, with maximum width at anterior fourth, at anterior margin wider than at pronotal base. PL 0.84–0.90 mm (HT 0.90 mm), PW 0.99–1.07 mm (HT 1.06 mm), PL/PW 0.84–0.85 (HT 0.85). Lateral margins rounded anteriorly, sinuated before hind angles. Anterior angles are rounded and obtuse, while posterior angles are sharp and pointed. Lateral furrows are wide and deep, with two pairs of setae. Anterolateral pair of setae situated in the anterior fifth of pronotal length, basolateral pair of setae before hind angles. Median furrow is well-developed, deep, visible on almost whole pronotum. Disc weakly convex.

Elytra : Elongate, sub-oval, glabrous, with maximum width at the middle, apically rounded (Fig. 2). EL 2.46–2.87 mm (HT 2.70 mm), EW 1.63–1.80 mm (HT 1.79 mm), EL/EW 1.51–1.60 (HT 1.60). Elytral base oblique. Shoulders rounded, sloped. Scutellum small, sub-triangular, with one pair of scutellar setae. Elytral striae 1–5 well-developed, deep, outer striae reduced to rows of foveae. Punctuation on striae dense and deep. Elytral stria 3 with two discal setae and one apical seta. First discal seta slightly below the level of second humeral seta. Second discal seta around the middle of elytra or slightly above. Intervals are somewhat convex (inner intervals more than outer ones). Disc weakly convex, almost flattened. The umbilicate series consists of eight setae on each elytron (four humeral, two median and two apical), while the humeral group of umbilicate pores is aggregated.

Legs : Long, slender, densely pubescent (Fig. 2), each protibia dorsally with a deep longitudinal fissure. The first two tarsomeres of male protarsi are distinctly dilated and toothed at the internal margin. The first male protarsomere is longer than wide. Tarsal claws are long and slender, pointed at the apex.

Abdomen : Ventrites 4–6 and anal ventrite are glabrous, each with one pair of setae posteriorly. Male abdominal sternite IX (urite) large, sub-triangular (Fig. 7).

Male genitalia : Aedeagus (Figs 4, 5) moderately long, AEL 0.59 mm (HT 0.59 mm). The median lobe is regularly curved and gradually narrowed apically in lateral view (Fig. 4), while almost straight, sub-parallel, with a rounded apex in dorsal view (Fig. 5). The basal bulb is relatively large (Figs 4, 5) and rounded in lateral view (Fig. 4). The copulatory piece is short, wide, unifid, in form of a shallow gutter with a longitudinal projection, rounded distally and shallowly incised proximally, weakly sclerotized except its edges and longitudinal projection (Fig. 6). The parameres are thin, each shorter than a half of aedeagus length, with four thick apical setae (Figs 4, 5).

Female genitalia : As presented in Fig. 8. Gonocoxites IX are relatively short and wide, curved, gradually narrowed apically, and basally joined with rounded, somewhat elongate gonosubcoxites IX.

So far known only from a cave and a pit, both situated on Mt. Tara (see the Type material). We assume that the subspecies could inhabit other caves and pits, as well as MSS on the same mountain and in its surroundings.

All specimens of D. (B.) semecensis tarensis ssp. nov. were collected by pitfall traps, both from the floor and walls in the innermost part of an unnamed cave in the village of Solotuša, and at the bottom of the pit 4-1-3-27 in the village of Kaluđerske Bare, in both cases in total darkness, at high humidity, and with the occurrence of trickling water. Pit 4-1-3-27 is the type locality of two additional subterranean beetle taxa – the leiodids Pholeuonopsis (Pholeuonopsis) tarensis Ćurčić & Pavićević, 2018 (Ćurčić et al. 2018b) and Proleonhardella (Proleonhardella) tarensis Ćurčić & Pavićević, 2021 (Ćurčić et al. 2021).

Holotype (by monotypy): male (NHMV) labeled as follows: „Höhle a. d. Semeč plan., Weirather“, with no date provided (white label, handwritten) / „Duvalius semecensis Wnl.“ (white label, handwritten) / „Holotypus Duvalius (Biharotrechus) semecensis Winkler, 1926 Ćurčić det. 2021“ (red label, printed) (Fig. 10).

For the purpose of comparisons, we studied one male specimen of D. (B.) semecensis borrowed from the NHMV, labeled as „Höhle a. d. Semeč plan. Weirather / Duvalius semecensis Wnl.“ (Figs 10–13), but with no red type label added. The handwriting on both white labels appears to be that of Albert Winkler (Figs 12, 13). According to the available data (H. Schillhammer, pers. comm.), all red type labels in the collection of Albert Winkler that belong to the NHMV have been added subsequently. It seems that Winkler didn’t add red type labels for his type specimens. In the original description of D. (B.) semecensis, it was indicated that Augusta Weirather collected one male specimen in an unnamed cave on Mt. Sjemeć in eastern Bosnia and Herzegovina (Winkler 1926). As the type series consists of only one male specimen with the same locality data, we designate the male specimen from the NHMV as the HT by monotypy of D. (B.) semecensis. According to Pretner (2011), who decoded the list of the cave and above-ground collecting sites visited by Weirather, the right name of the type locality of this taxon is the Vrteljka Cave, which is situated in the village of Đipi (43°44'35"N, 19°11'2"E) on Mt. Sjemeć, near the town of Višegrad, eastern Bosnia and Herzegovina. As we noted certain morphological intraspecific differences between the HT of D. (B.) semecensis from the NHMV and D. (B.) semecensis tarensis ssp. nov., the need of establishing nominotypical subspecies [D. (B.) semecensis semecensis] of D. (B.) semecensis has arisen.

After reading both the original description of D. (B.) semecensis by Winkler (1926) and its subsequent description by Jeannel (1928) and a careful examination of the HT of D. (B.) semecensis, we realized that some data on the morphology of the specimen listed in the previous literature do not correspond with the features of the observed male specimen. Namely, Jeannel (1928) reported that the head of D. (B.) semecensis semecensis is remarkably narrow, longer than wide, while Winkler (1926) didn’t mention this in the description. The former author claimed that its pronotum is narrow, not wider than long, while the second author wrote that its pronotum is slightly wider than long. Both authors said that both discal setae are situated in fourth elytral intervals. Additionally, Jeannel’s drawing of the specimen (Jeannel 1928) is not perfect as it doesn’t reflect its true shape (especially the head). Indeed, in the studied HT male, both head and pronotum are transverse, and the second discal seta is in the third stria (as was drawn by Jeannel 1928) (Table 1, Fig. 10). For these reasons, we decided to redescribe the HT of D. (B.) semecensis semecensis and to add here additional data on its morphology.

Medium-sized. TL 4.17 mm, L 4.40 mm.

Habitus : Body elongate. Colour reddish-brown. Legs and palpi paler.

Integument : Smooth, lustrous, head with a distinct isodiametric microsculpture, while microsculpture of both pronotum and elytra possesses both transverse and isodiametric meshes.

Head : Relatively large, around as long as 1/6 of TL, rounded (Fig. 10), narrower than pronotum, glabrous. Genae are rounded. Neck well-developed. HL 0.67 mm, HW 0.79 mm, HL/HW 0.85. Frontal furrows complete, deep, reaching neck constriction. Two pairs of supraorbital setae present, the anterior pair situated at the level of reduced eyes, while the posterior pair is near frontal furrows. Mandibles are thin, relatively long, sharply pointed, right one with a retinaculum. Labrum is deeply emarginate, with three pairs of setae. Clypeus is with two pairs of setae. Eyes are strongly reduced, oval, whitish, darkly bordered (Fig. 11), composed of 1–2 ommatidia. Antennae thin, long, haired, reaching almost half of elytral length when stretched backward. Antennomere 11 longest, followed by equally long antennomeres 1 and 3, antennomere 2 shortest (A2L/A2W 1.89), antennomeres 4 and 6–10 of similar length, antennomere 5 somewhat longer, A10L/A10W 2.60.

Thorax : Pronotum glabrous, transverse, cordiform (Fig. 10), slightly wider than long, with maximum width slightly before anterior third, at anterior margin wider than at pronotal base. PL 0.83 mm, PW 1.00 mm, PL/PW 0.83. Lateral margins rounded anteriorly, sinuated before hind angles. Anterior angles are rounded and obtuse. Posterior angles are sharp and pointed. Lateral furrows are relatively narrow and shallow, with two pairs of setae. Anterolateral pair of setae situated slightly before the anterior third of pronotal length, basolateral pair of setae before hind angles. Median furrow is well-developed, deep and long. Disc weakly convex.

Elytra : Elongate, sub-ovate, glabrous, with maximum width slightly after middle, apically rounded (Fig. 10). EL 2.56 mm, EW 1.55 mm, EL/EW 1.65. Elytral base oblique. Shoulders are somewhat prominent, obtuse and sloped. Scutellum is small, sub-triangular, with one pair of scutellar setae. Elytral striae 1–5 well-developed, deep, outer striae reduced to rows of foveae. Punctuation on striae dense and deep. First discal seta is in fourth interval, second discal seta is in third stria, while apical seta is positioned at place where second and third striae coalesce, slightly below the level of second humeral seta. First discal seta slightly before the level of third humeral seta. Second discal seta after the middle of elytra. Intervals are slightly convex (inner intervals more than outer ones). Disc relatively convex. The umbilicate series consists of eight setae on each elytron (four humeral, two median and two apical), while the humeral group of umbilicate pores is aggregated.

Legs : Elongate, thin, densely pubescent (Fig. 10), each protibia dorsally has a deep longitudinal fissure. The first two protarsomeres in the male are distinctly dilated and toothed at the internal margin. The first male protarsomere is longer than wide. Tarsal claws are long, thin, pointed apically.

Abdomen : Ventrites 4–6 and anal ventrite are glabrous, each with one pair of setae posteriorly. Male abdominal sternite IX (urite) missing, previously extracted from the male specimen.

Male genitalia : Aedeagus missing, previously extracted from the male specimen.

Female genitalia : Unknown.

So far known from its type locality (Vrteljka Cave) situated on Mt. Sjemeć. Eric Quéinnec (pers. comm.) collected specimens of the same taxon in MSS in the surroundings of the type locality, at both sides of the Drina River, close to the town of Višegrad in eastern Bosnia and Herzegovina.