Anthracus siamensis Jaeger 2015, nov.sp.
Creators: name: Jaeger, Bernd
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Anthracus
Anthracus siamensis

description: Anthracus siamensis nov.sp.
(Figs 21-23, 63-67, 69-73, 80)
Type material: Holotype: ♂ (NHMB) labelled "THAI, 26.IV.-6.V.1991 / UMPHANG 500m / 16°04'N 98°53'E / Vit Kubáň leg.", " Thailand' 91/" Thanon Thong Chai " / D. Král & V. Kubáň " and "HOLOTYPE ♂ / Anthracus / siamensis sp. n. / des. B. Jaeger 2015" [red label]. Paratypes: 2♂♂ (NHMB,) with same labels as the holotype. 1♂ labelled "THAI 28/4-6/5.91 / UMPHANG river / 16°07'N 99°00'E / lgt. D.Král 1000m " and " Thailand' 91/" Thanon Thong Chai " / D. Král & V. Kubáň ". 1♂ labelled "THAI 28/4-6/5.91 / UMPHANG 500m / 16 04'N 98°53'E / David Král lgt." and "Thailand' 91/"Thanon Thong Chai" / D. Král & V. Kubáň". 1♂ (MHNG) labelled " THAILAND 7.XI.86 / prov. Chiang Mai / Chiang Mai 320m / P. Schwendinger ". 6♂♂, 1♀ (NHMB, cJAE) labelled " LAOS-C; BOLI KHAM XAI prov. / PAKKADING; ~ 300m; / 18°20'N 104°00'E; / P. Pacholátko leg.: 1.-2.vi.2001 ". 2♂♂ (NHMB, cJAE) labelled " LAOS, 24-29.iv.2001 / Khammouan prov. / 18°07'N 104°29'E, / Ban Khoun Ngeun / - 200m, Vit Kubáň leg." All paratypes additionally with my label " PARATYPE ♂ or ♀ / Anthracus / siamensis sp. n. / des. B. Jaeger 2015 " [red].
Additional Material examined: 1♀ with same data as the holotype, and 4♀♀ with same data as the male paratypes from Pakkading. These females probably belong to A. siamensis, but differ externally more or less from the males from the same localities. They were excluded from the type series, because it cannot be ruled out that they belong to another similar species occurring sympatrically in Laos, Thailand or Myanmar.
Etymology: The species name refers to the known distribution of the species.
Description: General appearance as figured (Fig. 21). Body length 3.2-3.7 mm (HT 3.7 mm); width 1.3-1.4 mm.
Shiny, pronotum slightly, elytra moderately iridescent. Head and pronotum either dark brown to dark reddish brown, or paler reddish brown, with clypeus, labrum, and mandibles (inner margins and apices blackish) reddish yellow. Elytra paler than head and pronotum, paler to darker reddish yellow, with each elytron having a large blackish or dark brown central macula, expanding laterally to interval 7 or 8, and leaving base, apex and first interval reddish yellow. Legs and palpi pale yellowish brown, antennae with first two antennomeres yellowish brown, remaining ones moderately infuscated. Ventral surface mainly dark brown or dark reddish brown, with prosternum, epipleura, and sometimes medial part of abdominal sternites moderately paler.
Head (Figs 21-23) including eyes 0.78-0.83 times as wide as pronotum, with eyes moderately to distinctly prominent (head 1.61-1.71 times as wide as head between eyes). Labrum almost rectilinear or weakly rounded at apical margin, often somewhat sloped down to the right side. Mandibles medium sized, left mandible rather sharp at apex, not thickened or truncate. Antennae moderately long, 2.42-2.57 times as long as pronotum and 0.87-0.93 times as long as elytra. Microsculpture on clypeus distinct and almost isodiametric, on labrum weakly transverse, on frons with very lightly impressed (sometimes partly obliterated) and on vertex with moderately impressed isodiametric meshes becoming weakly transverse in front of pronotal apical margin.
Pronotum (Figs 21-23) 1.30-1.35 times as wide as long, 1.20-1.28 times as wide as head, widest in second quarter, lateral seta inserted a little posterior to beginning of second quarter. Apical margin almost rectangular or weakly emarginated, anterior angles narrowly rounded at tips, not, or weakly to moderately projecting forward. Sides convex in anterior half and rectilinearly narrowed to posterior angles, which are obtuse and weakly to moderately rounded. Basal margin sometimes rectilinear, sometimes weakly arcuate medially, and moderately to markedly oblique laterally. Lateral furrows moderately wide anteriorly, becoming weakly widened at posterior quarter, where they are fused with the baso-lateral impressions. Baso-lateral impressions medium sized, distinctly delimited from the convex pronotal disc and the weakly depressed medial part of base, flattened to basal and lateral margin. Anterior transverse impression almost obsolete. Microsculpture on disc with weakly impressed, moderately to strongly transverse meshes, and at basolateral impressions and lateral furrows with distinct weakly transverse meshes.
Elytra (Fig. 21) rather long, 1.53-1.61 times as long as wide, 2.71-2.85 times as long and 1.31-1.38 times as wide as pronotum. Sides weakly widened posteriad, widest at or just posterior to middle. Subapical sinuation weak. Elytral striae distinctly impressed and impunctate, intervals rather flat, becoming weakly narrowed and moderately convex at apex. Microsculpture on scutellum and around basal pore isodiametric, on elytral intervals only with traces of very lightly impressed transverse lines.
Metepisterna long and distinctly narrowed posteriad, at inner margin about 1.5 times longer than wide at basal margin. Prosternum medially with 6 and close to apical margin with a row of 9-10 medium long setae (often broken and then insertion points difficult to observe). Prosternal process with 1-2 distinct setae.
Protarsomeres 1-4 of males moderately and mesotarsomeres 2-4 weakly dilated. Protarsomere 4 markedly and mesotarsomere 4 moderately bilobed. Protarsomeres and mesotarsomeres 1-4 of males with biseriately arranged adhesive hairs on ventral surface.
Median lobe of aedeagus (Figs 63-67, 69-73) moderately large, with external shape as figured. Apical lamella rather short, not markedly narrowed (dorsal aspect), the apex abruptly bent upward (lateral aspect). Internal structures composed of one large apical tooth usually orientated to left side (lateral aspect), 0-3 medium-sized subapical teeth, 1- 3 small teeth in medial portion and 1-2 small and tall teeth somewhat beneath.
Comparisons A. siamensis nov.sp. is closely related to A. javaensis nov.sp. and A. skalei JAEGER, 2015 and obviously represents a closely related eastern vicariant of the latter. Both species are very similar in general appearance, microsculpture and body proportions which do not provide reliable differences to distinguish them. However, they differ by constant differences in the arrangement of teeth in the internal sac of the aedeagus (see Figs 62-75, 74-75) and partly also by the darker colour of head and pronotum (only darker specimens of A. siamensis).
A. siamensis is also very similar in general habitus to A. hornburgi nov.sp. which occurs in the adjacent areas of Myanmar, and to A. annamensis (BATES) and closely related taxa which occur in Myanmar, Laos and Thailand, at Chiang Mai even sympatrically. A. siamensis differs from A. hornburgi nov.sp. by the aedeagal characters given under this species, and from A. annamensis s.l. (Figs 78-79) by the different external shape of the median lobe of the aedeagus with the peculiar shape of the apex in lateral aspect and the different internal structures with large apical and subapical teeth (in A. annamensis and closely related taxa apex simple without any hook and teeth markedly smaller and with different arrangement). Externally there are often no reliable differences to differentiate A. siamensis from A. hornburgi and A. annamensis (incl. closely related taxa) but darker specimens differ from these taxa by their dark brown head and pronotum.
Distribution A. siamensis nov.sp. is so far known from Thailand and Laos (Fig. 80).
description: Published as part of Jaeger, Bernd, 2015, Revision of the maculate species of the Anthracus annamensis group from the East Palaearctic and Oriental Regions. Part 2. A redescription of Anthracus nesophilus (ANDREWES, 1936) and six new species from Nepal, India and SE Asia (Coleoptera, Carabidae, Harpalini, Stenolophina), pp. 1361-1396 in Linzer biologische Beiträge 47 (2) on pages 1374-1376, DOI: 10.5281/zenodo.5193661