Ischnosoma acutum, 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 : 200-201

Ischnosoma acutum spec. nov.

urn:lsid:zoobank.org:act:62214E44-BF50-4608-95B5-BDDA2B0936FC

( Figs 1–10 , 32 , 36 , Map 1 )

Type material: Holotype : “N 42°48'21 E 42°40'43 (25), Georgien Svaneti , Lentekhi NW 1240 m, Brachat & Meybohm 2.7.2017 / Holotypus  Ischnosoma acutum sp. n. det. V. Assing 2017” (cAss) . Paratype : “ 42°47'53 E 42°38'01 (17), Georgia Ratscha , Lentekhi 10 km W, 1100 m, Brachat & Meybohm, 20.V.2016 ” (cAss) .

Etymology: The specific epithet (Latin, adjective) alludes to the conspicuously acute apex of the ventral process of the aedeagus (ventral view).

Description: External characters ( Fig. 1 ) as in I. caucasicum , except as follows:

body somewhat smaller: body length 3.8–4.2 mm; length of forebody 1.7 mm; antennae somewhat shorter: length of antenna 1.3 mm; eyes slightly smaller; elytra with sutural series composed of 5–6 coarse punctures.

: sternite VII ( Figs 2–3 ) with an extensive cluster of dense pale short setae in postero-median portion and with nearly truncate posterior margin; sternite VIII ( Figs 4–5 ) with strongly concave posterior margin, near this concavity with conspicuously dense, long, relatively stout setae arranged in palisade fashion, anterior to this cluster with a cluster of dense pale and short setae; aedeagus ( Figs 6–10 ) 0.75 mm long, with the apex of ventral process conspicuously long and acute in ventral view and of characteristic shape in lateral view; internal structures, including apical internal structures, distinctly sclerotized; parameres with somewhat abruptly narrowed apex and each with 11–12 setae.

Comparative notes: Regarding the shapes and chaetotaxy of the male sternites VII and VIII, I. acutum is most simi-

lar to I. caucasicum and I. campbelli . Aside from its smaller size, somewhat shorter antennae, and the much longer and more acute apex of the ventral process of the aedeagus, the new species is distinguished from them as follows:

from I. caucasicum by the extensive cluster of dense fine setae on the male sternite VII ( I. caucasicum : with a small postero-median cluster of few stout setae), the shape and chaetotaxy of the male sternite VIII ( I. caucasicum : posterior margin less strongly concave, posterior portion with a more extensive cluster of transversely trapezoid shape with denser, more regular, and less stout setae not arranged in palisades, anterior to this cluster with a more extensive cluster of denser and longer pale setae), and by a longer aedeagus with internal structures of different shapes; from I. campbelli by less distinct microsculpture on the pronotum, fewer punctures along the elytral suture, less dense and slightly coarser punctation of the abdomen, the presence of a cluster of dense setae in the postero-median portion of the male sternite VII (absent in I. campbelli ), the shape and chaetotaxy of the male sternite VIII ( I. campbelli : posterior margin more strongly concave, posterior cluster of modified setae arranged in less dense palisades and narrower, median cluster of dense pale setae more extensive), and a more slender aedeagus with internal structures of different shapes.

For illustrations of I. caucasicum and I. campbelli see Figs 19–23 and KOCIAN (1997).

Distribution and natural history: The specimens were collected in two close localites near Lentekhi, on either of the border between Svaneti and Racha regions, Georgia ( Map 1 ). They were sifted from leaf litter in a mixed deciduous forest (type locality; Fig. 36 ) and on a north slope with hazelnut and beech at altitudes of 1240 and 1100 m, respectively (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 1–10: Ischnosoma acutum spec. nov.: forebody (1); male sternite VII (2); postero-median portion of male sternite VIII (3); male sternite VIII (4); postero-median portion of male sternite VIII (5); median lobe of aedeagus in lateral and in ventral view (6–8); apex of ventral process of aedeagus in lateral and in ventral view (9–10). Scale bars: 1: 0.5 mm; 2–8: 0.2 mm; 9–10: 0.1 mm.

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.

Fig. 36: Type locality of Ischnosoma acutum spec. nov. Photo: Heinrich Meybohm.

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.