Forinus mirus, Jałoszyński, 2022

Jałoszyński, Paweł, 2022, A warmth-loving brother of northern siblings: the first subtropical species of Forinus Kurbatov discovered on Okinawa-jima Japan (Coleoptera, Staphylinidae, Pselaphinae), Zootaxa 5188 (2), pp. 169-178 : 170-175

Forinus mirus sp. n.

( Figs 1–18 )

Type material. Holotype: JAPAN (Okinawa Pref.): ♂, two labels: „JAPAN, OKINAWA Pref. / OKINAWA-jima, N / Oura Bay , near mangrove / forest, sifted, 26 II 2020 / leg. P. JAŁOSZYŃSKI” [white, printed], “ FORINUS / mirus m. / HOLOTYPUS ” [red, printed] ( NSMT) . Paratype: ♂, „JAPAN, OKINAWA Pref. / OKINAWA-jima, N / Nago Castle Site / forest, sifted, 25 II 2020 / leg. P. JAŁOSZYŃSKI” (cPJ) .

Diagnosis. Two outer basal elytral foveae close to each other and both situated at anterior end of discal sulcus; metacoxa in male with posteromedian knob-like projection; abdominal sternite III in male with large dropshaped median process; sternite VI in male with small and inconspicuous brush of setae near each posterolateral margin; aedeagus in dorsal view with apical projections about as long as proximal bulbous region of median lobe, both projections in dorsal view strongly curved / recurved, with apices strongly bent mesad, in lateral view both projections weakly curved.

Description. Body of male ( Fig. 1 ) minute, slender and flattened, moderately and uniformly dark brown, setae whitish, cuticle moderately glossy; BL 1.11–1.18 mm.

Head ( Figs 3–4 ) subtrapezoidal, flattened, broadest at eyes, HL 0.20 mm, HW 0.24–0.25 mm. Vertex and sides of frons weakly convex except for distinct and sharply demarcated elongate subtriangular median impression on posterior margin of vertex and deep U-shaped frontal sulcus ( Fig. 3 ; fs) restricted to anterior half of head dorsum, complete and equally deep on entire length, posteriorly ending in round dorsal tentorial pits ( Fig. 3 ; dtp); eyes large, strongly convex and coarsely faceted; tempora in dorsal view subequal to eye length. Setiferous punctures on frons and vertex large, round and sharply marked but shallow, almost evenly and densely distributed except for slightly more sparsely punctate frontal sulcus, anterior margin of frons and small impunctate area on each supra-antennal tubercle; spaces between punctures equal to 0.3–2 diameters of punctures. Setae on frons and vertex dense, short and weakly suberect, those on sides of frons and vertex mainly directed mesad, those on frontal bulge delimited by frontal sulcus partly directed posterad, partly mesad, and partly anterad, setae in anterior region of frons directed anterad and anterolaterad; paired long setae lacking; several setae around dorsal tentorial pits and just anterior to them modified, broadly lanceolate. Genae, postgenae and submental region (area between posterior tentorial pits and posterior mental region) covered with punctures similar to those on frons and vertex, and with weakly suberect setae directed mainly anterad or (on sides of head) anterolaterad. Posterior tentorial pits ( Fig. 4 ; ptp) round and separated by distance about as wide as diameter of each pit; gular plate ( Fig. 4 ; gp) not delimited by gular sutures, on median area smooth, on sides with transverse reticulation.

Antennae ( Figs 5–6 ) much shorter than head and pronotum together; AnL 0.28 mm; scape indistinctly elongate; pedicel slightly broader than scape, indistinctly elongate; antennomeres 3–10 each distinctly transverse and from 7 gradually broadening; antennomeres 9–11 forming distinct club ( Fig. 6 ), 9 and 10 strongly transverse, 11 distinctly elongate and much longer than 9–10 combined. Scape and pedicel sparsely and unevenly covered with long erect setae; antennomeres 3–8 each with one ring of sparse erect setae; antennomeres 9–10 each with erect setae not forming distinct rings and distributed on entire surface, 10 additionally with sub-basal ring of several long digitiform sensilla; antennomere 11 densely covered with evenly distributed, long erect setae, one sub-median and one subapical ring of several long digitiform sensilla, apical region nearly symmetrical, lacking cavity.

Pronotum ( Fig. 3 ) rounded, broadest indistinctly behind middle; PL 0.23 mm, PW 0.24–0.25 mm. Anterior margin strongly arcuate; lateral margins strongly rounded, near and behind middle with papillate setal insertions, lateral margins just in front of posterior corners indistinctly sinuate; posterior margin weakly and evenly arcuate. Pronotal disc with median longitudinal sulcus ( Fig. 3 ; mls) developed as small elongate impression near anterior 1/3; pair of small but deep lateral antebasal foveae ( Fig. 3 ; laf) distinctly behind middle and each situated at mesal margin of large suboval lateral impression; small, shallow but sharply marked median antebasal fovea ( Fig. 3 ; maf) near posterior third; lateral and median foveae connected by narrow, sharply marked biarcuate, anteriorly convex antebasal groove ( Fig. 3 ; abg). Pronotal disc nearly evenly covered with punctures similar to those on frons and vertex, except for sparsely punctate lateral impression and impunctate median antebasal fovea; narrow area along posterior margin of pronotum with large, irregular in shape and dense alveolate punctures adjacent to each other, so that short and irregular longitudinal carinulae are formed between punctures, with one situated at middle behind median antebasal fovea. Basic vestiture of pronotal disc composed of dense, short and weakly suberect setae directed posterad (along midline) and posteromesad (on sides); additionally, lateral pronotal margins with modified, flattened and curved lanceolate setae.

Prosternum ( Fig. 4 ; pst) longer than procoxae, laterally fused with hypomera (i.e., notosternal sutures obliterated); anterior prosternal margin crenulate; anteromedian region with short and narrow longitudinal median carina; prosternal process between procoxae subtriangular and weakly elevated; hypomeron with deep longitudinal hypomeral groove ( Fig. 4 ; hg) bearing lateral fovea in precoxal region; distinct opening of fovea is also situated on prosternum just in front of each procoxa ( Fig. 4 ; foveae indicated by arrowheads). Basisternal region along anterior margin with irregular transverse row of large but shallow and diffuse setiferous punctures, inner region of each hypomeron anteriorly and laterally smooth and asetose, its adcoxal portion extending posterolaterad distinctly microreticulate.

Mesoscutellar shield largely hidden under posterior pronotal margin, only extremely small subtriangular tip exposed between elytral bases.

Elytra ( Fig. 7 ) together elongate subtrapezoidal with rounded sides, broadest near middle; EL 0.34–0.38 mm, EW 0.33–0.35 mm. Each elytron with complete sutural sulcus ( Fig. 7 ; ss), one short and diffuse discal sulcus in anterior 1/4 ( Fig. 5 ; ds), four dorsal basal elytral foveae ( Fig. 7 ; bef) of which two outermost are so close to each other that examined under stereomicroscope appear fused, and one lateral fovea not visible in dorsal view ( Fig. 7 , indicated by arrowhead). Posterolateral elytral corner obtuse-angled; posterior elytral margin shallowly sinuate; posterior sutural corner with small subtriangular projection. Punctures on elytra similar to those on pronotal disc but smaller near base, gradually and slightly increasing in diameter posteriorly and those near posterior elytral margin are slightly larger than those on pronotum. Setae dense, short and suberect, most directed posterad (on middle elytral region), slightly posterolaterad (along suture) and slightly posteromesad (on sides); several modified, flattened lanceolate setae are distributed near basal elytral foveae and similar setae are also distributed in one row just in front of posterior elytral margin.

Hind wings well developed, functional.

Mesoventrite ( Fig. 8 ; v 2 ) transverse, with lateral regions fully demarcated from metaventrite. Mesoventral intercoxal process subtriangular, elongate, posteriorly rounded and overlapped by anterior metaventral process. Subtriangular area posterior to procoxal rests and mesoventral intercoxal process covered with scale-like microsculpture; sides of mesoventrite smooth and asetose. Ona pair of foveae is situated on mesoventrite (indicated by arrowhead in Fig. 6 ) on sides posterolaterad procoxal rests and filled with flattened lanceolate setae.

Metaventrite ( Fig. 8 ; v 3 ) distinctly transverse and weakly convex at sides, flattened at middle, with distinct narrow subtriangular and directed anterad anterior metaventral process, which, together with mesoventral process, separates mesocoxae. Metaventrite with one pair of lateral foveae, just behind and laterad mesocoxal cavities (foveae indicated by arrowhead in Fig. 8 ); diffuse ridge extends from each metaventral fovea toward posterolateral metaventral corner. Metaventrite covered with dense, small and shallow punctures much smaller than those on head, pronotum and elytra, base of anterior metaventral process with several large, irregular and shallow punctures adjacent to each other, posterior margin of each mesocoxal rest with broad carina oblique to the long body axis and impunctate; katepisternal sutures along posterior margins of metaventrite accentuated by dense row of unevenly distributed larger punctures. Setae on metaventrite dense and weakly suberect, those on median area directed posterad, those on sides posteraolaterad.

Legs short and robust, fore and hind legs slender, with slightly sinuate femora brodest between middle and distal third; middle legs ( Fig. 10 ) with distinctly thickened femora and longitudinal row of dense thick setae along distal 1/3 of outer margin; metacoxae modified, each with posteromedian knob-like coxal process ( Fig. 9 ; cxp).

Abdomen ( Figs 9 , 11–14 ) about as long as elytra, AbL 0.35–0.38 mm, AbW 0.29–0.30 mm. Tergites IV–VI subequal in length, VII distinctly longer than VI; tergites IV–VI each with sharply marked discal carinae ( Fig. 11 ; dc): on tergite IV in anterior half strongly diverging posterad and in distal half parallel, only slightly shorter than length of tergite, on tergite V parallel and reaching posterior 1/3, on tergite VI parallel and reaching middle of tergite, area between posterior ends of carinae on each tergite much narrower than 1/3 width of segment. Surface of tergites and laterotergites densely covered with punctures much smaller thoan those on elytra, and densely covered with short, nearly recumbent setae directed posterad or (on tip of abdomen) posteromesad. Sternite III ( Fig. 9 ) with distinct transverse metacoxal rests posteriorly demarcated by arcuate carinae and finely longitudinaly rugose, metacoxal rests separated at middle by large, drop-shaped and ventrally slightly impressed median sternal process ( Fig. 9 ; msp); sternite VI ( Fig. 12 ) with small setal brush directed posteromesad and situated on sublateral posterior area. Surface of all sternites with punctures and setae similar to those on tergites. Sternite IX ( Figs 12–14 ) completely divided into small subtriangular lateral portions and median penial plate, in intact specimens ( Fig. 14 ) plate appears symmetrical and slightly longitudinally oval, but dissections reveal clearly asymmetrical shape of those regions of penial plate that are situated beneath surrounding sclerites.

Aedeagus ( Figs 15–18 ) elongate and strongly asymmetrical, lacking any setae; AeL 0.20 mm; median lobe in dorsal view with asymmetrical and slightly elongate basal capsule, bearing small sublateral proximal projection; distal portion of aedeagus demarcated by distinct sub-median constriction, strongly asymmetrical, bearing elaborate complex of elongate projections, one situated on abparameral, other on parameral side of median lobe; in lateral view projections are weakly curved / recurved, in dorsal view both projections are strongly recurved and their distal regions are bent mesad with apices far beyond longitudinal axis of aedeagus.

Female. Unknown.

Distribution. Okinawa Island, Ryūkyū Archipelago, Japan.

Etymology. The Latin adjective mirus means wonderful, marvelous, astonishing, extraordinary, amazing. Finding this species, distributed so far from formerly known Forinus , on the beautiful subtropical Okinawa-jima, was a truly amazing and unexpected discovery.

Remarks. Forinus mirus clearly differs from two previously described species ( Kurbatov 1991, 1992) in unique structures of the aedeagus. As shown in Fig. 2 , the apical projections, situated on parameral and abparameral side of the strongly asymmetrical aedeagus, are of different shapes in the three currently known species. Whereas the projections in lateral view in F. macer and F. secundus are extremely slender, relatively simple and both strongly curved, those in F. mirus are distinctly stouter, more complex in shape and weakly curved. The knob-like modifications of metacoxae and the large median process of the abdominal sternite III in males are also unique for the Okinawan species.

Figures

FIGURES 1–2. Forinus mirus sp. n., male. Dorsal habitus (1); distribution of all nominal Forinus species with aedeagi in lateral view compared (illustrations for F. macer and F. secundus after Kurbatov (1991, 1992), respectively) (2).

FIGURES 3–4. Forinus mirus sp. n., male. Head, pronotum and elytral base in dorsal view (3); head and prothorax in ventral view (4). Abbreviations: abg, antebasal groove; dtp, dorsal tentorial pit; fs, frontal sulcus; gp, gular plate; hg, hypomeral groove; laf, lateral antebasal fovea; maf, median antebasal fovea; mls, median longitudinal sulcus; pst, prosternum; ptp, posterior tentorial pits. Arrowheads indicate ventral prothoracic foveae.

FIGURES 5–6. Forinus mirus sp. n., male. Right antenna in dorsal view (5) and right antennal club in dorsal view (6).

FIGURES 7–8. Forinus mirus sp. n., male. Left elytron in dorsal view (7); pterothorax and abdominal base in ventral view (8). Abbreviations: bef, basal elytral foveae; ds, discal sulcus; ss, sutural sulcus; v2, mesoventrite; v3, metaventrite. Arrowheads indicate foveae.

FIGURES 9–10. Forinus mirus sp. n., male. Metacoxal region in ventral view (9); distal region of left middle leg in dorsal view (10). Abbreviations: cxp, coxal process; msp, median sternal process; sIII‒IV, sternite III‒IV; v3, metaventrite.

FIGURES 11–14. Forinus mirus sp. n., male. Abdomen in dorsal (11) and ventral (12) views; isolated penial plate (13); abdominal apex in ventral view (14). Abbreviations: dc, discal carina; III‒IX, abdominal segments III‒IX.

FIGURES 15–18. Forinus mirus sp. n., male. Aedeagus in dorsal (15, 17) and lateral (16, 18) views.