Baraxina Raffray, 1896

Hlaváč, Peter & Jałoszyński, Paweł, 2021, The Pselaphinae (Coleoptera: Staphylinidae) of New Caledonia and Loyalty Islands. IV. Revision of the genus Baraxina Raffray, 1896, Zootaxa 4941 (2), pp. 193-216 : 194-201

Baraxina Raffray, 1896

Baraxina Raffray, 1896: 301 . Type species: Baraxina francoisi Raffray, 1896 (monotypy).

Diagnosis. Head lacking rostrum, with setose frontal fovea and setose dorsal tentorial pits, ventrally with prominent median gular carina; maxillary palpi much longer than head, with palpomere 2 clavate, gradually broadening distad and weakly curved, palpomere 3 small, sub-quadrangular with rounded external margin, palpomere 4 strongly elongate, in proximal half nearly cylindrical, distally evenly tapering toward pointed apex, sensory appendage present and slender; maxillary palpomeres 2–4 sparsely covered with modified setae broadening distad and curved outwards. Mentum elongate. Antennae composed of 11 antennomeres, club trimerous, indistinctly delimited, antennomeres 9 and 10 modified in males; antennomere 11 in both sexes with subapical impression bearing a conical group of several basiconic sensilla. Pronotum with distinct setose median and lateral foveae, lacking antebasal sulcus. Hypomera subdivided into narrow inner and broad outer regions; hypomeral groove present, shallow. Each elytron with three asetose basal foveae, lacking striae and carinae. Mesoscutellar shield minute, barely visible between elytral bases, with fine median longitudinal carina, delimited from fused scuto-scutellar region by deep constriction. First visible abdominal tergite (IV) with large transverse mediobasal fovea and two lateral foveae, all filled with modified, lanceolate setae. Aedeagus with weakly sclerotized, symmetrical or slightly asymmetrical median lobe, asymmetrical elongate endophallic sclerites (indiscernible in one species), and elongate parameres.

Redescription: Body ( Fig. 1) elongate, moderately slender, strongly or moderately convex, glossy in most species; bicoloured, head, maxillary palpi and pronotum dark brown to pitchy black, elytra, abdomen and legs reddish-brown; length 1.70–2.15 mm, maximum width 0.65–0.90 mm.

Head elongate subtrapezoidal, lacking rostrum. Temples round, clearly longer than eyes; lateral carina ( Fig. 2 ; lc) distinct, complete, extending from anteroventral margin of eye to lateral mandibular articulation; vertex and frons confluent, weakly convex; dorsal tentorial pits (= vertexal foveae of Chandler (2001)) setose, large, situated between eyes; large frontal fovea setose, situated in impression between prominent supra-antennal tubercles; eyes strongly convex, small, finely faceted. Neck region retracted into prothorax short, subcylindrical, with well-defined gular plate ( Fig. 2 ; gp) laterally demarcated by weakly marked gular sutures; posterior tentorial pits ( Fig. 2 ; ptp; = gular foveae of Chandler (2001)) large, circular, situated in front of transverse impression demarcating neck region ventrally; pre-tentorial gular-submental region elongate, with broad, prominent median gular carina ( Fig. 2 ; mgc) broadest anteriorly and gradually narrowing posterad.

Antennae ( Figs 1, 7–8 ) composed of eleven antennomeres, slender, shorter than body; antennal insertions broadly separated. Scape cylindrical, about twice as long as wide, over twice as long as pedicel, antennal club trimerous and indistinctly demarcated, antennomere 11 ( Fig. 7 ; a 11 ) elongate, asymmetrical and subconical, with small subapical impression bearing a subconical group of several basiconic sensilla ( Fig. 8 ; bcs).

Labium ( Figs 2–3 ) with elongate mentum ( Fig. 3 ; mn), which is inversely subtrapezoidal, broadest at anterior margin, with sinuate sides and a pair of long anterolateral setae; prementum ( Fig. 3 , pmn) short, trapezoidal, largely membranous, lacking ligula; labial palpi ( Fig. 3 , lp) dimerous, palpomere 1 short, annular, 2 nearly five times as long as 1, with three apical setae of which one is conspicuously long; lateral lobes of hypopharynx ( Fig. 3 ; llh) elongate, each with dense fringe of short trichia along mesal margin and with 3–4 long apical setae.

Maxilla with large cardo ( Fig. 3 ; cd) bearing long lateral submedian seta; basistipes ( Fig. 3 ; bst) triangular, elongate, with one long and one short lateral sub-basal setae; mediostipes ( Fig. 3 ; mst) subtriangular, not longer than basistipes, with one median apical seta; galea and lacinia ( Fig. 3 ; gal, lac) elongate and each with a fringe of dense, thick setae along mesal margin; palpifer ( Fig. 3 ; ppf) elongate, broadening distad, with one short submedian lateral seta, one long subapical mesal seta, and one short apical seta. Maxillary palpi ( Fig. 5 ) much longer than head and slender, palpomeres 2–4 with sparse, short, spatulate setae curved outwards, palpomere 1 ( Fig. 5 ; mxp1) minute, elongate, about twice as long as broad; palpomere 2 ( Fig. 5 ; mxp2) about 3.5 times as long as broad, at base indistinctly narrower than palpomere 1, gradually thickening distad and slightly curved; palpomere 3 ( Fig. 5 ; mxp3) distinctly broader than 2 but much shorter, only slightly elongate, with external margin rounded and inner margin angulate; palpomere 4 ( Fig. 5 ; mxp4) strongly elongate, slightly longer than 1 and 2 combined, with oblique base, nearly cylindrical in proximal half and evenly, gradually tapering distad to pointed apex, with apical sensory appendage ( Figs 5–6 ; SA) rod-like, long and slender.

Mandibles ( Fig. 3 ; md) subtriangular, slightly convex dorsally and concave ventrally, large, with sharp apical tooth and five triangular, pointed mesal pre-apical teeth gradually reducing in length toward mandibular base; external mandibular margin with two conspicuously long setae.

Labrum (not shown) transverse with rounded anterior and lateral margins; anteroventral margin with a pair of peg-like sensilla ( Fig. 4 ; ps).

Pronotum ( Fig. 1) slightly wider than long, widest near middle, with lateral margins strongly rounded and indistinctly sinuate in posterior half, anterior pronotal margin shorter than posterior, anterior corners not marked, posterior corners distinct, obtuse-angled. Pronotal disc with small median and large, setose lateral antebasal foveae, lacking antebasal sulcus.

Prosternum ( Fig. 9 ; pst) laterally fused with hypomera; basisternal region slightly longer than coxal region, setose, with pair of large, widely separated setose lateral procoxal foveae ( Figs 9–10 , lpcf; term of Chandler (2001); in fact, these foveae are situated on prosternum, anterad procoxal cavities), median procoxal fovea absent; prosternal process ( Fig. 9 , psp) subtriangular, not separating procoxae. Hypomera divided by incomplete hypomeral ridges ( Fig. 9 ; hyr) into narrow, elongate and microsculptured inner region ( Fig. 9 ; ihy) and broad, smooth outer region ( Fig. 9 ; ohy), the latter with shallow hypomeral groove ( Fig. 9 ; hyg).

Mesonotum ( Fig. 11 ) with mesocutum and mesoscutellum fused ( Fig. 11 ; sc2+scl2), subtriangular; scutellar shield ( Fig. 11 ; scs) oval, with median longitudinal carina, demarcated by deep constriction, visible between elytral bases.

Metanotum not studied.

Mesoventrite ( Figs 12–13 ) laterally largely demarcated from metaventrite, with massive prepectus ( Fig. 12 ; pr), anteromedian asetose transverse impression functioning as procoxal rest ( Fig. 12 ; pcr), transverse median mesoventral fovea ( Figs 12–13 , mmvf), a pair of lateral mesoventral foveae ( Figs 12–13 , lmvf), and a pair of lateral mesocoxal foveae ( Fig. 12 ; lmcf; term of Chandler (2001); in fact these foveae are laterad mesocoxae, on metaventrite just behind mesoventrite), all foveae filled with lanceolate setae. Mesoventral ridge ( Fig. 12 , mvr) distinct, step-wise, reaching anterior margin of mesocoxae, demarcating median setose region from lateral glabrous areas. Mesocoxae narrowly separated by elongate, subtriangular mesoventral process ( Fig. 12 ; msvp) with rounded apex reaching middle of mesocoxae, meeting anterior tip of anterior metaventral process ( Fig. 12 ; amtp), both processes flat. Metaventrite ( Fig. 12 ) strongly transverse; posterior margins of mesocoxal rests carinate; lateral metaventral foveae ( Figs 12–13 , lmvtf) large, narrowly separated, filled with lanceolate setae, metaventral process ( Fig. 12 , mtvp) broad and short, with slightly concave posterior margin.

Elytra ( Figs 1, 14–15 ) together subtrapezoidal, longer than both pronotum and abdomen, each elytron with three asetose basal foveae ( Fig. 14 ; bef; Fig. 15 ), lacking striae and carinae.

Abdomen ( Figs 1, 16 ) densely pubescent, with first two visible (IV–V) tergites subequal in length, IV ( Fig. 16 ) with transverse mediobasal fovea ( Fig. 16 ; mbf) between short discal carinae ( Fig. 16 ; dc), IV–VII with basolateral foveae ( Fig. 16 ; blf) adjacent to paratergites ( Fig. 16 ; pt), all foveae filled with lanceolate setae. First three visible paratergites well-developed. Second visible sternite (IV) densely setose, clearly longer than third (V) which is lacking basolateral foveae.

Legs ( Figs 1, 12 ) long and slender, all femora clavate, tibiae and tarsi slender; tarsi longer than half length of tibiae.

Aedeagus ( Figs 17 –43) elongate, with weakly sclerotized and symmetrical or slightly asymmetrical median lobe; endophallic sclerites elongate and asymmetrically distributed (in one species indiscernible), parameres long and slender, with or without apical setae.

Sexual dimorphism. Males with modified, asymmetrical distal antennomeres, metaventrite and abdominal sternites medially impressed, legs (profemora and protibiae) in some species modified, with projections, spines or spurs.

Remarks. The prominent and wide median gular carina (median gular longitudinal elevation sensu Kurbatov & Sabella, 2015: 299) present in Baraxina places this genus in the Rybaxis group of Chandler (2001: 292). Within this group, Baraxina can be readily separated by a combination of the following characters: (1) head with frontal fovea and dorsal tentorial pits; (2) maxillary palpomere 2 slender at base, evenly thickening distad, about as long as 4, and palpomere 3 subquadrangular; (3) pronotum with median and lateral antebasal foveae, lacking antebasal sulcus; (4) each elytron with three basal foveae, lacking striae and carinae; and (5) the first visible (IV) abdominal tergite with transverse setose mediobasal fovea between short discal carinae, the latter reaching at most one third of tergal length, and with setose basolateral foveae. Moreover, adults of Baraxina are usually bicoloured, with the head, abdomen and pronotum clearly darker than the reddish-brown elytra, abdomen and legs, a pattern rarely found among world Brachyglutini . However, this unusual pigmentation occurs in many unrelated New Caledonian beetle families and subfamilies (including other Pselaphinae) (PJ, pers. obs.), a phenomenon that remains unexplained.

Other nominal Brachyglutina genera known to occur in New Caledonia can be separated from Baraxina as follows:

- Eupines King, 1866 by pronotum and elytra lacking foveae;

- Anasopsis Raffray, 1904 by maxillary palpomere 4 asymmetrical, short, and maxillary palpomeres 3 and 4 each with one large patch of recumbent, modified setae;

- Kieneriella Yin & Hlaváč, 2016 by elongate maxillary palpomere 3;

- Physoplectus Reitter, 1882 by elytral flanks with subhumeral foveae, and by well-defined marginal, sutural and discal striae.

Natural history. Baraxina species are associated with dead wood in tropical forests, as the majority of the studied specimens were collected by sifting moist rotten wood, and by pyrethrum fogging of trees and logs, or taken from subcortical habitats. Some specimens were also collected by sifting leaf-litter and by flight intercept traps. No other details concerning ecology of Baraxina are known.

Distribution. Endemic to New Caledonia, known only from the main island of La Grande Terre.

Key to males of the genus Baraxina ( B. francoisi not included)

1 Profemora lacking spine................................................................................ 2

- Profemora with straight or curved basal spine............................................................... 5

2 Maxillary palpomere 4 slender, over five times as long as wide; palpomere 3 strongly transverse, subquadrate with external margin projecting; antennomeres 5 and 6 subequal; protibiae lacking preapical spine.............. .. B. grimbacheri sp. n.

- Maxillary palpomere 4 stout, less than four times as long as wide; palpomere 3 subrectangular with external margin rounded; antennomere 5 longer than 6; protibiae with well-defined preapical spine......................................... 3

3 First visible abdominal tergite with discal carinae barely discernible, basal impression not sharply delimited................................................................................................... B. amieuana sp. n.

- First visible abdominal tergite with discal carinae short but sharply marked, basal impression well-defined............... 4

4 Protibiae with subapical expansion; palpomere 4 less than 2.7 times as long as wide; antennomere 9 slightly transverse............................................................................................... B. rutai sp. n.

- Protibiae lacking subapical expansion; palpomere 4 more than 4 times as long as wide; antennomere 9 as long as wide......................................................................................... B. kanakorum sp. n.

5 Antennomere 9 as long as wide or longer than wide. .......................................................... 6

- Antennomere 9 clearly transverse, at least 1.25 times as wide as long. ............................................ 8

6 First visible abdominal tergite with discal carinae reaching basal third of tergite; palpomere 4 less than 4.75 times as long as wide................................................................................................ 7

- First visible abdominal tergite with discal carinae shorter or absent; palpomere 4 more than 4.85 times as long as wide............................................................................................ B. poroana sp. n.

7 Antennomeres 9 and 10 each as long as wide; antennomere 11 0.21 mm long; pronotum slightly shorter than head.............................................................................................. B. lescheni sp. n.

- Antennomeres 9 and 10 each longer than wide; antennomere 11 0.23–0.24 mm long; pronotum slightly longer than head. ........................................................................................ B. monteithi sp. n.

8 Body length below 1.78 mm .............................................................. B. burwelli sp. n.

- Body length over 1.82 mm .............................................................................. 9

9 Antennomere 10 as long as wide; discal carinae on first visible abdominal tergite absent.............. B. aoupinica sp. n.

- Antennomere 10 transverse; discal carinae on first visible abdominal tergite present................................ 10

10 Discal carinae on first visible abdominal tergite not reaching basal third of tergite.................................. 11

- Discal carinae on first visible abdominal tergite reaching basal third of tergite..................................... 12

11 Palpomere 4 over 5 times as long as wide; aedeagus in dorsal view symmetrical........................ B. jenisi sp. n.

- Palpomere 4 less than 4.5 times as long as wide; aedeagus in dorsal view asymmetrical............. B. asymmetrica sp. n.

12 Apex of maxillary palpomere 2 with strong round projection on external side..................................... 13

- Apex of maxillary palpomere 2 lacking projection, simply rounded............................................. 14

13 Antennomere 5 about 1.3 times as long as 6; head as long as wide or longer; pronotum about as long as head..................................................................................................... B. wanati sp. n.

- Antennomere 5 about 1.15 times as long as 6; head wider than long; pronotum slightly longer than head..... B. pecki sp. n.

14 Basal spine on profemora curved; maxillary palpomere 4 0.32–0.33 mm long; scape 0.12–0.13 mm long; ratio length / width of antennomere 10 = 0.87–0.91............................................................. B. dzumacana sp. n.

- Basal spine on profemora straight; maxillary palpomere 4 0.26–0.29 mm long; scape 0.15–0.16 mm long; ratio length / width of antennomere 10 = 0.67–0.78. ......................................................................... 15

15 Ratio length / width of antennomere 9 = 0.60–0.67, ratio length / width of antennomere 10 = 0.67–0.69; ratio of lengths of antennomeres 5/6 = 1.06–1.25; aedeagus with three groups of endophallic sclerites in submedian and subapical regions. ......................................................................................... B. koghisiana sp. n.

- Ratio length / width of antennomere 9 = 0.75–0.82, ratio length / width of antennomere 10 = 0.72–0.78, ratio of lengths of antennomeres 5/6 = 1.29–1.38; aedeagus with one group of endophallic sclerites in submedian region.................................................................................................. B. parakoghisiana sp. n.

Figures

FIGURES 2–6. Baraxina sp. n., female. Head in ventral view (2); mouthparts in ventral view (3); median portion of anterior margin of labrum in anteroventral view (4); left maxillary palpus in ventral view (5); close-up of apex of maxillary palpomere 4 in ventral view (6). Abbreviations: bst, basistipes; cd, cardo; gal, galea; gp, gular plate; lac, lacinia; lc, lateral carina; llh, lateral lobe of hypopharynx; lp, labial palpus; md, mandible; mgc, median gular carina; mn, mentum; mst, mediostipes; mxp, maxillary palpus; mxp1–4, maxillary palpomere 1–4; pm, prementum; ppf, palpifer; ps, peg-like sensillum; ptp, posterior tentorial pit; SA, sensory appendage.

FIGURES 7–8. Baraxina sp. n., female. Distal portion of right antenna in ventral view (7); and close-up of sensory area of antennomere 11 (8). Abbreviations: a9–11, antennomere 9–11; bcs, basiconic sensillum.

FIGURES 9–13. Baraxina sp. n., female. Prothorax in ventral view (9); lateral procoxal fovea (10); mesonotum in dorsal view (11); pterothorax in ventral view (12); and meso- and metaventral foveae (13). Abbreviations: amtp, anterior metaventral process; hyg, hypomeral groove; hyr, hypomeral ridge; ihy, inner region of hypomeron; lmcf, lateral mesocoxal fovea; lmtvf, lateral metaventral fovea; lmvf, lateral mesoventral fovea; lpcf, lateral procoxal fovea; mmvf, median mesoventral fovea; msvp, mesoventral process; mtvp, metaventral (intermetacoxal) process; mvr, mesoventral ridge; ohy, outer region of hypomeron; pcr, procoxal rest; pcxc, procoxal cavity; pr, prepectus; pst, prosternum; sc2+scl2, fused mesoscutum and mesoscutellum; scs, scutellar shield;

FIGURES 14–16. Baraxina sp. n., female. Elytral base in dorsal view (14); opening of elytral fovea (15); abdominal tergite IV (first visible) in dorsal view (16). Abbreviations: bef, basal elytral fovea; blf, basolateral fovea; dc, discal carina; mbf, mediobasal fovea; pt, paratergite.

FIGURES 17–30. Aedeagus in dorsal (17, 18, 20, 22–24, 26–29) and lateral (19, 21, 25, 30) views. Baraxina francoisi Raffray (17); B. amieuana sp. n. (18–19); B. grimbacheri sp. n. (20–21); B. kanakorum sp. n. (22); B. rutai sp. n. (23); B. aoupinica sp. n. (24–25); B. asymmetrica sp. n. (26); B. burwelli sp. n. (27); B. dzumacana sp. n. (28); B. jenisi sp. n. (29–30).