A new subspecies of the genus Duvalius Delarouzée, 1859 (Coleoptera, Carabidae, Trechini) from western Serbia, with a key and an annotated catalogue of Serbian Biharotrechus and Duvalius s. str. taxa

Duvalius semecensis tarensis ssp. nov. from two subterranean sites situated on Mt. Tara (western Serbia) is described, illustrated and compared with its most related congeners. It is provisionally placed in the subgenus Biharotrechus Bokor, 1922. The new subspecies is characterized by a depigmented, medium-sized body, the presence of reduced eyes, deep and complete frontal furrows, two pairs of discal setae in third elytral striae, as well as by the shape of aedeagus. It inhabits caves on Mt. Tara and is endemic of this mountain. Data on the distribution and bionomy of the new subspecies are given. Its closest relative, Duvalius ( Biharotrechus ) semecensis semecensis Winkler, 1926, is redescribed and we designated its holotype by monotypy. A key for the identification and an annotated catalogue of Serbian Biharotrechus and Duvalius s. str. taxa are also provided.

Several field trips conducted by the third (MK) and the fourth author (FB) at two subterranean sites on Mt. Tara resulted in the discovery of a series of specimens belonging to the genus Duvalius Delarouzée, 1859. Subsequent analysis of the beetles yielded that they belong to a Duvalius subspecies unknown to science, which is described and diagnosed in this contribution.

Materials and methods
The diagnosis of Duvalius (Biharotrechus) semecensis tarensis ssp. nov. is based on the study of type series, which consists of 13 specimens (two males and 11 females). Specimens were collected by pitfall trapping during 2013, 2014 and 2017 at two subterranean sites on Mt. Tara (an unnamed cave in the village of Solotuša and the pit 4-1-3-27 in the village of Kaluđerske Bare) (Fig. 1). Pitfall traps were baited with rotten meat.
The specimens were studied by the first (SĆ) and the second author (NV) in the laboratory of the Institute of Zoology, University of Belgrade -Faculty of Biology, Belgrade, Serbia. Studied specimens were dissected, analyzed and illustrated. Dry beetles were glued onto separate paper mounting cards. Morphological structures of the beetles were examined using Nikon SMZ 800N and Zeiss Stemi 508 stereomicroscopes. Male and female genitalia were dissected, cleaned in KOH, fixed in a medium consisting of Canada balsam and xylol, mounted on transparent plastic mounting cards and pinned under examined specimens. Macro photographs were taken by a Nikon SMZ 800N stereomicroscope with a Nikon DS-Fi2 digital camera and improved using Adobe Photoshop CS6 software. A Nikon DS-L3 control unit was used for scaling.

Abbreviations of measurements
A2L/A2W ratio of length to width of antennomere 2; A10L/A10W ratio of length to width of antennomere 10; AEL length of aedeagus; EL length of elytra (measured along suture from base to apex); EL/EW ratio of length of elytra to maximum width of elytra; EW maximum width of elytra; HL length of head (measured from the anterior margin of clypeus to neck constriction); HL/HW ratio of length of head to maximum width of head; HW maximum width of head; L overall body length (measured from the apex of mandibles to the apex of elytra along suture); PL length of pronotum (measured along median line); PL/PW ratio of length of pronotum to maximum width of pronotum as greatest transverse distance; PW maximum width of pronotum as greatest transverse distance; TL total body length (measured from the anterior margin of clypeus to the apex of elytra along suture).  (Figs 9,10,14,16,18,19) (Winkler 1926;Jeannel 1928;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.

Collections
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).
) 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). ) 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).
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.
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.
Geographic distribution. 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.

Duvalius (Biharotrechus) semecensis semecensis
Remarks. 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.  (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 pro- notum 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.
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. Geographic distribution. 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.

Discussion
The geographic range of the trechine genus Duvalius is large. It ranges from the Iberian Peninsula in the west to China in the east, as well as from central Europe in the north to northern Africa in the south. Its highest diversity is observed in the Apennine and the Balkan Peninsulas, as well as in the Alps (Jeannel 1928;Belousov 2017). This genus is exceptionally diverse and highly polymorphic and includes principally small-to medium-sized taxa (Jeannel 1928;Lorenz 2005;Belousov 2017). Their pigmentation is mostly absent, but certain taxa are pigmented. Eyes can be differently developed -lacking, reduced, or functional. Most Duvalius representatives are associated with subterranean habitats (chiefly caves and soil) (Jeannel 1928).
The genus Duvalius in the Balkan Peninsula, including Serbia, contains a high number of taxa (Lorenz 2005;Belousov 2017). The validity of some recently described taxa has been widely discussed by Lohaj et al. (2013) and Ćurčić et al. (2013). Some of them were in the past placed in newly established genera (Ćurčić et al. 2001; Ćurčić et al. 2003a, 2003b), which were later synonymized (Lohaj et al. 2013). Ćurčić et al. (2013) re-erected those to the genus level. Most authors treat the genus as a monophyletic unit Faille et al. 2013;Lohaj et al. 2013), as was previously established by Jeannel (1928), but the support of this branch is not yet proven (and probably depends on the taxonomic sampling used). Namely, the monophyly of different Duvalius subgenera was not supported so far (Faille et al. 2013) and the organization within this group remains to be refined. Eric Quéinnec (pers. comm.) considers the genus Duvalius monophyletic and probably a sister group to the genus Anophthalmus Sturm, 1844, but thinks that the current subdivision of Duvalius into subgenera will probably be debatable as the boundaries of subgenera are not yet clear. However, Ćurčić et al. (2013) are of opinion that Duvalius contains a number of genera based on the heterogeneity of morphological features of species ascribed to the genus. It is very important to elucidate the phylogenetic position of Duvalius subgenera and species groups, as well as of the related genera in the Balkans in the future because phylogenetic relationships among different taxa of Duvalius in this area still remained unclear. It is essential to conduct further molecular phylogenetic studies, which are independent of the subjectivity of taxonomists (contrary to the classical morphological and morphometric observations that depend on the subjective view of taxonomists).
According to morphological features, Duvalius semecensis tarensis ssp. nov. is provisionally ascribed to Biharotrechus Bokor, 1922 rather than to Duvalius s. str. as it predominantly shares morphological characters specific to the former subgenus. This might also concern D. (D.) javorensis, D. (D.) suvoborensis and D. (D.) suvodolensis, which seem to form a homogeneous group of closely related species, but it must be first supported by morphological analyses of the copulatory piece [the case of D. (D.) suvodolensis] and desirably by molecular studies. According to the shape of the copulatory piece, the new subspecies is close to Duvalius str. representatives. Namely, lateral phaneres in D. (B.) semecensis tarensis ssp. nov. are reaching the apex of the copulatory piece, while these structures in Biharotrechus spp. are short (Jeannel 1928), indicating that the subgenus Biharotrechus has very debatable morphological characters and is probably questionable.
In total, seven taxa of Duvalius s. str. and one taxon of Biharotrechus currently occur in Serbia (Fig. 9). As indicated in the differential diagnosis, D. ) suvodolensis likely belong to a separate group of species as they share numerous morpho-anatomical features (reduced eyes, complete and deep frontal furrows, smooth genae, the specific position of the humeral setae and the similar shape of the copulatory piece) (Pavićević and Popović 2001;Ćurčić et al. 2003a, 2003b. They were even the members of a single genus -Javorella S. Ćurčić, Brajković & B. Ćurčić, 2003Ćurčić, Brajković & B. Ćurčić, (Ćurčić et al. 2003aĆurčić, Brajković & B. Ćurčić, , 2003b. The species Duvalius (Duvalius) bolei Pretner, 1963 has a specific position within the subgenus Duvalius s. str. and is not closely related to D. (B.) semecensis tarensis ssp. nov. The former taxon is the only Duvalius s. str. species distributed in the Carpatho-Balkanides of Serbia. Pretner (1963) was aware of the supraspecific position of the taxon and assumed that it might belong to a separate subgenus of Duvalius. Based on the characteristic shape of the head, the absence of longitudinal furrows on the fore tibias, the peculiar shape of the aedeagus and the specific form of the copulatory piece, Ćurčić and Brajković (2003) placed the taxon in the newly established genus Curcicia Ćurčić & Brajković, 2003. The Serbian taxa of the subgenera Biharotrechus and Duvalius s. str. can be separated using the identification key below, followed by their catalogue, including data on their type localities, other localities in Serbia, distribution and short notes.   Hlaváč et al. (2017), it seems that Belousov (2017) wasn't aware of the data published in Nonveiller (1983) and Pavićević et al. (2012), who reported the presence of the nominotypic subspecies of Duvalius (Duvalius) sturanyi (Apfelbeck, 1904) at two sites in Serbia in the vicinity of the towns of Ljubovija and Prijepolje. to study and photograph certain Duvalius species from his collection. We are especially indebted to Dr Harald Schillhammer (Natural History Museum Vienna, Vienna, Austria), who kindly loaned the type material of some ground beetle taxa. Last but not least, we are grateful to Dr Snežana Pešić (Kragujevac, Serbia), Dr Eric Quéinnec (Paris, France) and Dr Pier Mauro Giachino (Turin, Italy), whose opinions, useful suggestions and constructive remarks significantly contributed to the improvement of earlier versions of the manuscript.