Ischnosoma barbigerum, Assing & Schülke, 2017

Assing, Volker & Schülke, Michael, 2017, On the Ischnosoma fauna of Georgia (Coleoptera: Staphylinidae: Tachyporinae), Beiträge Zur Entomologie = Contributions to Entomology (Beitr. Entomol.) 67 (2), pp. 195-206 : 201

Ischnosoma barbigerum spec. nov.

urn:lsid:zoobank.org:act:314DE8C9-E254-4171-A502-F710E896BCFD

( Figs 11–18 , 37 , Map 1 )

Type material: Holotype : “N 42°49'02 E 42°01'52 (10), Georgien Svaneti , Jvari ca. 20 km N 600 m, Brachat & Meybohm 25.6.2017 / Holotypus  Ischnosoma barbigerum sp. n. det. V. Assing 2017” (cAss).

Etymology: The specific epithet (Latin, adjective: bearded) alludes to the characteristic clusters of dense setae on the male sternite VIII.

Description: Body length 4.3 mm; length of forebody 2.0 mm; length of antenna 1.3 mm. Elytra with sutural series composed of 5–7 moderately coarse punctures. Based on external characters ( Fig. 11 ) indistinguishable from the geographically close I. acutum .

: sternite VII ( Figs 12 , 33 ) with an extensive cluster of dense pale short setae in postero-median portion and near posterior margin with modified short and stout setae; sternite VIII ( Figs 13–14 ) with moderately concave posterior margin, in postero-median portion with a transverse cluster of very dense long setae not arranged in palisades, anterior to this cluster with dense shorter and paler setae; aedeagus ( Figs 15–18 ) 0.7 mm long, apex of ventral process subapically abruptly narrowed in ventral view and very acute in lateral view; basal internal structures distinctly, apical internal structures weakly sclerotized; parameres regularly tapering apicad and with 10–11 setae each.

Comparative notes: Ischnosoma barbigerum is readily distinguished from the externally similar I. acutum , the only other representative of the I. spelaeum group recorded from Svaneti, by the shape and chaetotaxy of the male sternite VIII and by the completely different shape of the apex of the ventral process of the aedeagus. It differs from I. caucasicum , which it most resembles in the chaetotaxy of the male sternite VIII, by slightly smaller body size, smaller eyes, shorter antennae, a male sternite VII with an extensive postero-median cluster of dense short setae, a male sternite VIII with a narrower posterior cluster of shorter and less dense setae and with less stout long black setae on either side of the posterior median setae, and by a more slender aedeagus with a less broad ventral process (ventral view), with a much more slender and acute apex of the ventral process (lateral view), and with internal structures of different shapes. For illustrations of I. caucasicum see Figs 19–23 .

Distribution and natural history: The type locality is situated to the north of Jvari, Svaneti region, Georgia ( Map 1 ). The holotype was sifted from leaf litter near a stream in a mixed deciduous forest ( Fig. 37 ) at an altitude of 600 m (MEYBOHM pers. comm.).

Figures

Map 1: Distributions of species of the Ischnosoma spelaeum group in the Caucasus region, based on revised and reliable records: I. caucasicum (white circles); I. barbigerum (black triangle); I. acutum (white diamonds); I. myops (black circles). Grey circle: doubtful locality “Helenendorf” (today Göygöl).

Figs 11–23: Ischnosoma barbigerum spec. nov. (11–18) and I. caucasicum from Krasnaya Polyana (19–23): forebody (11); male sternite VII (12); male sternite VIII (13, 19); postero-median portion of male sternite VIII (14, 20); (15–16, 21–22) median lobe of aedeagus in lateral and in ventral view; apex of ventral process of aedeagus in lateral and in ventral view (17–18, 23). Scale bars: 11: 0.5 mm; 12–16, 19–22: 0.2 mm; 17–18, 23: 0.1 mm.

Fig. 37: Type locality of Ischnosoma barbigerum spec. nov. Photo: Heinrich Meybohm.

Figs 24–35: Ischnosoma molle spec. nov. (24–32), I. barbigerum spec. nov. (33), and I. caucasicum, paratype (34–35): forebody (24); male sternite VII (25, 34); postero-median portion of male sternite VIII (27, 33, 35); male sternite VIII (27); postero-median portion of male sternite VIII (28); median lobe of aedeagus in lateral view (29–30); apex of ventral process of aedeagus in lateral and in ventral view (31–32). Scale bars: 24: 0.5 mm; 25–30, 33–35: 0.2 mm; 31–32: 0.1 mm.