Lomechusoides umbrosus Kjærby, Craig, Thomsen & Hansen, 2026, sp. nov.

Lomechusoides umbrosus sp. nov. Figs 2 A, 2 C, 2 E, 2 F, 2 I, 2 K, 7 A Type locality. Hammarskog, Uppsala, Uppland, Sweden. 59.774586, 17.578827. Material examined. Holotype: Sweden • 1 ♂; Hammarskog, Uppland; 59.774586, 17.578827; 20. IX. 2023; leg. H. Kjærby; w. Formica polyctena; NHMD. Paratypes: Belarus • 4 ♂♂, 1 ♀; Vitebsk reg., Polotsk distr., 3 km SW of Novopolotsk, near the lake Luechovo, 55.5168, 28.6318, 152 m, in the nest of Formica polyctena, fir-wood, sorrel, 30. V. 2013, leg. E. Pliskevich; cSem • 1 ♂; Vitebsk reg., Polotsk distr., 3 km SW of Novopolotsk, near the lake Luechovo; 55.5167, 28.6325; 152 m; 10. VI. 2015; leg. E. Pliskevich; in the nest of Formica polyctena, fir-wood, sorrel; cSem. Russia • 2 ♀♀; Smolensk distr., near Vysokoye; 54.73, 32.21; 23. V. – 11. VI. 2022; leg. O. Semionenkov; window trap near dead spruce and nest of Formica polyctena, coniferous-broad-leaved forest; cSem • 1 ♂, 3 ♀♀; Svedlovsk Reg., Visimskij Nature Res.; 57.3734, 59.7734; 570 m; 18. VI. 2019; leg. A. Solodovnikov, A. K. Hansen, A. Tokareva; spruce dominated forest, in Formica nests; NHMD. Sweden • 1 ♀; Hacksta, Uppland; 59.55, 17.38; 30. IV. 2022; leg. H. - E. Wanntorp; w. Formica polyctena; cWann • 1 ♂; Hållvik, Uppland; 59.93, 18.41; 12. V. 2025; leg. H. - E. Wanntorp; cWann • 3 ♂♂, 4 ♀♀; Hammarskog, Uppland; 59.77, 17.57; 20. IX. 2023; leg. H. Kjærby; w. Formica polyctena; cKjær • 6 ♂♂, 3 ♀♀; Skåne, Vittsjö; 56.34, 13.66; Formica rufa nest; 24. V. 1980; leg. A. Carlson; MZLU. Additional material. Estonia • 1 ♂; Välgi; 58.55, 26.92; 18. V. – 7. VII. 2024; forest edge window trap on dead spruce; TAMZ. Finland • 1 ♀; Karelia australis, Joutseno, Kuurmanpohja; 61.073, 28.729; 71 m; 8. VI. 2015 – 11. VII. 2015; leg. Eero Helve; window trap, mushroomed log pile (aspen, spruce, birch); ZMUO. Poland • 1 ♀; Bialowieza, Czerlonka; 52.69, 23.72; 19. VI. 1991; leg. L. Borowiec; DBET. Differential diagnosis. The new species can be separated from all other members of the Lomechusoides strumosus group sensu Jászay et al. (2023) by the following combination of characters: 1) widest point of the pronotum positioned at ~ ¼ – ⅓ of the length of the pronotal lateral margin from the posterior corners, making the posterior corners distinctly obtuse. 2) pronotal lateral margins smoothly rounded in their entire length 3) a visible sharp margin on the posterior curved part of the pronotal margins (best viewed laterally and slightly from behind) (Fig. 2 G). 4) pronotal disc glossy with very limited, uneven microsculpture, but with very well-defined tubercles. 5) head, sternites and tergites predominantly black. 6) clypeus and frontal median impression of the head shiny with limited, uneven microsculpture. 7) two transverse carinae on the anterior part of visible tergites II to V connected in the centre of the tergite by a broad septum, occasionally two or more broad septa, rarely absent. See Table 2 for a comprehensive list of identified traits that separate L. umbrosus sp. nov. from its close congener L. strumosus. Description. Female. Measurements (mm): TL 6.81; FL 3.07; AL 3.34; HW 0.91; HL 0.94; PW 1.99; PL 1.20; EW 2.24; EL 0.96; FTL 1.30; MTL 1.66; HTL 1.95. Ratios: HW / HL 0.96; PW / PL 1.66; EW / EL 2.33. Male. Measurements (mm). TL 6.46; FL 2.88; AL 2.90; HW 0.84; HL 1.08; PW 1.72; PL 1.04; EW 2.07; EL 0.94; FTL 1.25; MTL 1.47; HTL 1.75. Ratios: HW / HL 0.78; PW / PL 1.65; EW / EL 2.2. Colouration dark. Legs and antennae dark reddish-brown. Head entirely black. Pronotal disc deep bordeaux reddish-brown, with a semicircular blackish pattern along the posterior margin; the pronotal lateral margins are paler reddish-brown than the pronotal disc. Elytra almost entirely bright reddish-brown, blackish-brown along anterior margins. Thorax with sterna black. Tergites and sternites almost entirely black, each with a thin reddish-brown transverse stripe along the posterior margins. Head rectangular, with deep V-shaped frontal median impression very weakly microsculptured, shiny, very sparsely and finely punctate (Fig. 2 H). A central spot at the hind part of the head without microsculpture. Clypeus finely and unevenly microsculptured, shiny. The rest of the head is evenly microsculptured and finely punctate, dull. Eyes slightly to strongly protuberant. Temples overall concave, usually being strongly narrowed immediately behind the eyes, subparallel posteriad. Antennae (Fig. 2 D) relatively gracile and long (Fig. 3 B). Male with dense tufts of golden pubescence on antennal segments III – IV. Male. Scape 1.52 × as long as wide, and 1.8 × as long as pedicel; pedicel 1.31 × as long as wide; antennomere III 1.89 × as long as wide; antennomere IV 1.4 × as long as wide; antennomeres V – VIII all ~ 1.5 × as long as wide; terminal antennomere slender and acute, 3.25 × as long as wide, 1.36 × as long as scape. Female. Scape 1.6 × as long as wide, and 1.68 × as long as pedicel; pedicel 1.26 × as long as wide; antennomere III 1.86 × as long as wide; antennomere IV 1.41 × as long as wide; antennomeres V – VIII all ~ 1.4–1.6 × as long as wide; terminal antennomere slender and acute, 2.9 × as long as wide, 1.37 × as long as scape. Pronotum (Fig. 2 J) with concave anterior margin; anterior corners obtuse; with visible microsculpture along anterior and posterior margins, and in depressions. Pronotal lateral margins are smoothly rounded, semicircular convex and with strong microsculpture. The widest point of the pronotum ~ ¼ – ⅓ of the lateral marginal length from the posterior corners. As the pronotum narrows from the widest point towards the anterior corners, the lateral margins are evenly rounded without angular bends. Behind the widest point, the pronotum narrows slightly posteriorly, making the posterior corners distinctly obtuse. This results in the pronotal lateral margins being smoothly rounded in their entire length. In lateral view, the pronotal lateral margins are thick in the anterior half, then abruptly thinning in the posterior half. At posterior corners the margin is strongly curved and very thin with a visible sharp edge (Fig. 2 G). The length of sharp edge-bearing margin varies but is usually rather short and constrained to the curved part at posterior corners. The pronotal lateral margins are separated from the pronotal disc by shallow longitudinal depressions with the lateral area with visible microsculpture. Pronotal disc (Fig. 2 J) with either very limited, unevenly distributed fine microsculpture, or no microsculpture at all, giving the central part of the pronotum a very glossy appearance. Pronotal disc with well-defined tubercles and median line. Pronotal tubercles are very noticeable due to the lack of surrounding microsculpture. Pronotal tubercles bearing long, thin erect golden pubescence. Lateral margins of pronotum with 5–7 black macrosetae, anterior margin with 1–4 black macrosetae. Metaventral process microsculptured and sparsely punctate with concave anterior and lateral margins, possessing lateral lines that converge anteriorly. Anterior part with no / very weakly defined transverse carina, posterior part of median line lacking lentil-like depression. Metaventral disc microsculptured and sparsely punctate with weakly defined longitudinal shallow impressions on either side of the posterior part of the median line. Elytra finely and evenly punctate and microsculptured. Each puncture bears a short golden hair. Anterior part bearing eight or nine black macrosetae, humeral part with two black macrosetae. Abdomen with visible tergite I densely punctate and evenly microsculptured; II and III densely punctate along posterior margin, otherwise finely and sparsely punctate, finely, and unevenly microsculptured. Visible tergites IV and VII finely and sparsely punctate and finely and unevenly microsculptured; visible tergites V – VI equally finely and sparsely punctate in median part, lateral parts bearing slightly larger and denser punctures and more visible microsculpture. Visible tergites I – IV with dense golden trichomes laterally, visible tergites I – III additionally with shorter, golden trichomes along posterior margin, thinning towards the centre. Visible tergites V – VII without trichomes. Anterior part of visible tergites II – V bearing two transverse carinae. The two carinae are joined near the centre of the tergite by a septum (Fig. 2 L). Occasionally, two or more connecting septa may be present, and rarely they may be absent. Area around the two transverse carinae with wavy microsculpture. Posterior parts of visible tergites I – III, especially II, with numerous black macrosetae. Posterior margins of visible tergites IV – VII with fewer, smaller dark setae. Sternites I – IV finely microsculptured and sparsely punctate, rather glossy. Sternite V and especially VI more strongly microsculptured and moderately punctate. Max distance between punctures on sternite VI is ~ 4 × the diameter of punctures. Sternites I – III with dense, flat-laying, golden trichomes laterally in the anterior part. All sternites with numerous black macrosetae. Male genitalia. Aedeagus (Fig. 4 B, D) with robust median lobe, apical lobe shorter than basal bulb. In lateral view, apex is thin, with a subapical expansion followed by a notch (Fig. 4 D). In lateral view, the entire dorsal margin of the chitinised part of the median lobe is concave. In dorsoventral view, apex is relatively thin, roughly shaped like an acute triangle, sides of median lobe softly concave. In ventral view, lateral sides of apical lobe narrow apically along entire length, most strongly narrowing in basal part. Apex of parameres with a short, backwards-curving tooth. Female genitalia. Spermatheca (Fig. 4 F) with basal and apical parts approximately equal in length; basal part 0.88–1.16 × the length of apical part; tip of apical part rounded. The entire spermatheca is uniformly dark brown. Etymology. The species epithet umbrosus, meaning shadowy in Latin (nominative mascul