Euconnus (Tetramelus) melkei, Jałoszyński, 2022

Jałoszyński, Paweł, 2022, Euconnus (Tetramelus) melkei sp. n., a bizarre South African ant-like stone beetle (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5091 (1), pp. 155-172 : 157-162

Euconnus (Tetramelus) melkei sp. n.

( Figs 1–19 )

Type material studied. Holotype ( RSA: Eastern Cape): ♂, two labels: “RSA (E) E Cape10-90 m/ -31.6486/29.506, 28.11.2019 / Silaka Reserve Iliwa trail / Gxwaleni river valley / leg. P. Jałoszyński PJ#10” [white, printed], „ EUCONNUS / (TETRAMELUS) \ melkei m. \ P. Jałoszyński, 2021 \ HOLOTYPUS“ [red, printed] (TMSA).

Diagnosis. Head in male conspicuously, monstrously modified, broader than pronotum, with pair of lateral subtriangular vertexal elevations each bearing lateral penicillus, fishtail-shaped median frontal projection, pair of directed mesad frontal lateral projections, pair of lateral frontal elevations, and pair of narrow frontal grooves; scape strongly modified, with dorsodistal ‘stump’ as broad as remaining portion of scape, truncate at apex and with group of modified setae on truncate area; pronotum much longer than wide, broadest near anterior margin, with pair of deep, narrow sublateral grooves; protrochanter strongly modified, with long thorn-like ventral projection; profemur distinctly enlarged and with bisinuate ventral margin; aedeagus in ventral view with inversely subtriangular, distally broadened and truncate apex, strongly asymmetrical and complex assemblage of endophallic sclerites; each paramere with multiple apical and subapical setae of various lengths and thickness, including setae directed distad, laterad and ventromesad, one subapical lateral seta unusually thick.

Description. Body of male ( Fig. 1 ) strongly elongate, moderately convex; pigmentation dark brown, with legs, antennae and palps distinctly lighter; body covered with setae slightly lighter than cuticle; BL 1.95 mm.

Head ( Figs 1–7 , 19 ) broadest at eyes, shortly behind antennal insertions, distinctly transverse and broader than pronotum, HL 0.35 mm, HW 0.43 mm; tempora in dorsal view nearly 2.5 × as long as eyes, behind eyes straight and strongly converging posterad, shortly in front of occipital constriction abruptly bent at obtuse angle and angulate; frontoclypeal groove lacking; clypeus transverse and weakly convex; frons between antennal fossae with pair of arcuate frontal grooves ( Fig. 3 ; fg) demarcating median subtrapezoidal region, which is prolonged posteriorly by median frontal projection ( Figs 2–3 , 5–6 ; mfp), which is fishtail-shaped and bears fringe of flat cuticular projections forming two lateral groups, two pairs of thick setae are inserted just in front of median frontal projection, projection is flanked by pair of lateral frontal projections ( Figs 2–3 , 5–6 ; lfp) which are curved mesad and each bears several apical cuticular processes; frons near posteromesal margin of each eye with deep supraocular pit ( Figs 2–3 ; sop); area posteromesad each pit bulging, forming pair of broadly separated frontal elevations ( Figs 2–3 , 6 ; fe); sides of vertex flattened, median region of vertex forming pair of large, subtriangular and weakly separated at middle vertexal elevations ( Figs 1–4 ; vte), each bearing two penicilli of vertexal setae ( Figs 2–4 , 7 ; vts). Eyes small, weakly convex, nearly round, adjacent to antennal fossae ( Fig. 4 ). Small, dense, shallow and diffuse punctures are present on frons: on small median area behind median frontal projection and on frontal elevations; remaining areas virtually impunctate; clypeus with two oblique lateral rows of setae (long anterior and short posterior); sparse, moderately long and suberect setae are also distributed on lateral frontal projections, frontal and vertexal elevations; short, sparse and suberect setae are distributed on each temple; extremely short and dense, nearly recumbent setae form a small patch behind each supraocular pit; posterolateral regions of frontal elevations and flattened lateral regions of vertex laterad and posterad frontal elevations covered with extremely short, sparse, barely noticeable setae (these areas appear asetose under stereomicroscope). Ventral surface of head ( Fig. 9 ) flattened, hypomeral ridges ( Fig. 9 ; hr) strongly sinuate and posteriorly reaching posterior tentorial pits, although their posterior halves are weakly elevated and diffuse; posterior tentorial pits ( Fig. 9 ; ptp) situated in front of transverse impression demarcating neck region ventrally, strongly elongate, slot-like; genae and postgenae smooth and sparsely setose.

Antennae ( Figs 1–4 , 8 ) conspicuously slender, gradually thickening distad, AnL 1.03 mm, scape ( Fig. 8 ; sc) from base to insertion of pedicel 2.3 × as long as broad, curved dorsad (ventrally convex), with apical projection which is as broad as distal half of scape, subcylindrical, with truncate apex directed dorsad and bearing group of modified, short setae on its proximal half; pedicel ( Fig. 8 ; pd) much shorter than scape, nearly twice as long as broad; antennomeres 3–8 each strongly elongate, 9–10 each weakly elongate, 11 shorter than 9–10 combined, twice as long as broad.

Pronotum ( Figs 1 , 10–11 , 19 ) strongly elongate and flattened, broadest just behind anterior margin; PL 0.50 mm, PW 0.39 mm. Anterior margin nearly straight; anterior corners broadly rounded; sides nearly straight and distinctly converging posterad; posterior corners obtuse-angled and relatively poorly marked; posterior margin straight; pronotum with distinctly flattened disc ( Fig. 11 ) bearing pair of deep and narrow longitudinal sublateral grooves ( Fig. 10 ; slg) and one (inner) pair of shallow but well visible antebasal pits ( Fig. 10 ; abp). Disc virtually impunctate, with sparse, moderately long and suberect thin setae distributed mainly in anterior and posterior thirds, sides laterad each sublateral groove with moderately dense thick bristles, similar bristles and a few thin setae are also distributed on deflexed sides of pronotum (i.e., hypomera), along anterior portions of hypomeral ridges. Basisternal region of prosternum ( Fig. 9 ; bst) shorter than coxal region, with transverse row of anteriorly-directed setae; prosternal process marked as weakly elevated median longitudinal ridge, in natural position hidden between procoxae. Notosternal sutures ( Fig. 9 ; nss) complete and well-visible. Hypomera subdivided into narrow and strongly curved inner (adcoxal) region strongly convex laterad procoxal cavity, and broad but less convex outer region; hypomeral ridges ( Figs 9, 11 ; hyr) demarcating outer and inner regions of each hypomeron present but incomplete, obliterated at the level of procoxal cavities (well-visible in lateral view; Fig. 11 ).

Elytra ( Figs 1 , 10 ) together oval, broadest between anterior third and middle; EL 1.10 mm, EW 0.69 mm, EI 1.60; humeral calli prominent, elongate, basal impressions short and shallow; two basal elytral foveae ( Fig. 10 ; bef) small but deep, poorly visible under stereomicroscope; elytral apices separately rounded. Punctures fine and inconspicuous; setae moderately long and dense, suberect.

Mesoventrite ( Figs 11–12 ) with pair of impressed and setose procoxal rests ( Fig. 12 ; pcr) and strongly elevated, keel-like mesoventral intercoxal process ( Figs 11–12 ; msvp); in lateral view ( Fig. 11 ) on each side of mesoventrite two pits can be seen: ventrolateral and dorsolateral fovea ( Fig. 11 ; vlf, dlf).

Metaventrite ( Fig. 12 ) unmodified, with short metaventral intercoxal process ( Fig. 12 ; mtvp) broadly separating metacoxae, with distinctly concave posterior margin.

Legs ( Fig. 1 ) long and slender, front legs with modifications: protrochanter ( Fig. 13 ; tr1) with long ventral thornlike projection, and profemur ( Fig. 14 ) distinctly enlarged in relation to meso- and metafemur, with ventral margin bisinuate, anterior surface impressed near sub-basal third and near middle, with sub-basal impression covered with tiny tubercles and sub-median impression filled with short, dense setae.

Aedeagus ( Figs 15–18 ) elongate, AeL 0.43 mm; median lobe in ventral view broadest near sub-basal third and gradually narrowing distad up to subapical region, where it is abruptly narrowed and forming slender, long apical projection with broadened and truncate apex; ventral wall with movable subtriangular subapical plate closing ostium; ventral diaphragm large and oval; median lobe in lateral view strongly curved in basal region, nearly bent and a right angle; endophallic structures complicated, with several asymmetrical and darkly sclerotized components, most notably several elongate, curved and pointed sclerites; parameres slender and long, each with unique pattern of apical and subapical setae of various lengths and thickness, including setae directed dorsad, laterad and ventromesad, and one conspicuously thick lateral subapical seta.

Female. Unknown.

Distribution. SE South Africa (NE region of Eastern Cape, near Port Saint Johns).

Etymology. This remarkable species is dedicated to Andrzej Melke, the most prolific researcher on the faunistics of the Staphylinidae of Poland, who prematurely passed away in October 2021, leaving so many friends in a deep grief.

Remarks. No other nominal species of Euconnus has such elaborate and monstrous male cephalic structures, neither a strongly modified scape. The holotype male was collected by sweeping a forest undergrowth with entomological net in a relatively dry area.

Figures

FIGURES 1–4. Euconnus melkei sp. n., holotype male. Dorsal habitus (1); head in dorsal (2), anterodorsal (3) and lateral (4) views. Abbreviations: fe, frontal elevation; fg, frontal groove; lfp, lateral frontal projection; mfp, median frontal projection; sop, supraocular pit; vte, vertexal elevation; vts, vertexal setae.

FIGURES 5–8. Euconnus melkei sp. n., holotype male. Median region of frons in dorsal (5) and anterodorsal (6) views; left lateral region of vertex in dorsal view (7); proximal region of left antenna in dorsal view (8). Abbreviations: fe, frontal elevation; fg, frontal groove; lfp, lateral frontal projection; mfp, median frontal projection; pd, pedicel; sc, scape; vte, vertexal elevation; vts, vertexal setae.

FIGURES 9–11. Euconnus melkei sp. n., holotype male. Head, prothorax and anterior region of mesothorax in ventral view (9); prothorax and elytral base in dorsal view (10); prothorax and anterior region of pterothorax in lateral view (11). Abbreviations: abp, antebasal pit; bef, basal elytral fovea; bst, basisternal region of prosternum; dlf, dorsolateral fovea; hr, hypostomal ridge; hyr, hypomeral ridge; msvp, mesoventral process; nss, notosternal suture; ptp, posterior tentorial pit; slg, sublateral groove; vlf, ventrolateral fovea.

FIGURES 12–14. Euconnus melkei sp. n., holotype male. Pterothorax and abdomen in ventral view (12); proximal region of left leg in ventral view (13); left femur in ventral view (14). Abbreviations: cx1, procoxa; fe1, profemur; msvp, mesoventral process; mtvp, metaventral process; pcr, procoxal rest; tr1, protrochanter.

FIGURES 15–18. Euconnus melkei sp. n., holotype male. Aedeagus in ventral (15, 17) and lateral (16, 18) views.

FIGURES 19–20. Comparison of males of Euconnus melkei sp. n. (19) and E. paranasicornis Franz (20; paratype); anterior half of body.