Ischnosoma acre, Assing, 2019

Assing, Volker, 2019, New species and additional records of Ischnosoma from Georgia (Coleoptera, Staphylinidae, Tachyporinae), Linzer biologische Beiträge 51 (2), pp. 773-788 : 775

Ischnosoma acre nov.sp. ( Figs 1 , 9-12 , 17-19 , 26-27 , Map 1 )

T y p e m a t e r i a l: Holotype ♂: " GEORGIA [44] - Imereti, S Bagdati, 42°00'50''N, 42°48'56''E, 270 m, deciduous forest margin, 21.VII.2019, V. Assing / Holotypus ♂ Ischnosoma acre sp. n. det. V. Assing 2019" (cAss) . Paratypes 1♂: " N41°51'37 E42°46'59, Georgien Imeretien (54), Sairme S 1890 m, 19.5.2018, Brachat & Meybohm" (cAss) ; 1♂: " N42°00'50 E42°48'55, Georgien Imeretien (50), Baghdati 290 m 18.5.2018, Brachat & Meybohm" (cAss) .

E t y m o l o g y: The specific epithet (Latin, adjective: acute) alludes to the acute apex of the ventral process of the aedeagus in ventral view.

D e s c r i p t i o n: Body length 4.7-5.0 mm; length of forebody 2.1-2.2 mm. Habitus as in Fig. 1 . External characters as in I. solodovnikovi SCHÜLKE, 2001 and I. molle ASSING & SCHÜLKE, 2017. Distinguished only by the male primary and secondary sexual characters.

♂: sternite VII ( Figs 17 , 26-27 ) with a cluster of moderately dense thin setae in posteromedian portion, posterior margin truncate; sternite VIII ( Figs 18-19 ) with a cluster of moderately dense long and thin setae in postero-median portion, posterior margin shallowly triangularly excised; aedeagus ( Figs 9-12 ) approximately 0.7 mm long; ventral process apically very acute in ventral view; internal structures shaped as in Figs 9-12.

C o m p a r a t i v e n o t e s: Based on the external and the male sexual characters, I. acre is undoubtedly closely allied to I. solodovnikovi from Northeast Turkey (Trabzon, Rize) and I. molle (Southwest Georgia: Adjara: western Meskheti Range). It is distinguished from these species as follows:

from I. solodovnikovi by smaller body size, longer and thin setae near the median portion of the truncate posterior margin of the male sternite VII, a shorter and less slender male sternite VIII with denser pubescence in the postero-median portion, and by a smaller aedeagus (I. solodovnikovi: 0.78-0.90 mm long; n = 6) with a significantly more acute apex of the ventral process (ventral view) and with less strongly sclerotized internal structures of different shapes (for comparison see Figs 15-16 , 23-25 , 30-31 );

from I. molle by longer and less stout pubescence in the postero-median portion of the male sternite VII, a male sternite VIII with a smaller, less deep, and more triangularly shaped posterior margin (broadly concave in I. molle ) and with a less distinctly delimited and less extensive cluster of much less dense and longer pubescence in the posteromedian portion, and a slightly smaller aedeagus with an apically more acute ventral process (ventral view) and with sclerotized internal structures of slightly different shapes.

D i s t r i b u t i o n a n d n a t u r a l h i s t o r y: The type specimens were found in two localities in the north slope of the Meskheti Range, Imereti region, Southwest Georgia ( Map 1 ) at altitudes of 270-290 and 1890 m. They were sifted from chestnut leaf litter, from litter near rocks (MEYBOHM pers. comm.), and from leaf litter in a deciduous forest margin.

Figures

Map 1: Distributions of the species allied to Ischnosoma solodovnikovi and of I. thoracicum: I. solodovnikovi (white triangles), I. molle (black circles; white circle: doubtful female-based record), I. acre (black triangles), and I thoracicum (white star.

Figs 1-8: Ischnosoma acre (1), I. cuspidatum (2), I. convergens (3-4), I. parallelum (5-6), and I. myops (7-8): (1-3, 5, 7) habitus; (4, 6, 8) head and pronotum in lateral view. Scale bars: 1-3, 5, 7: 1.0 mm; 4, 6, 8: 0.5 mm.

Figs 9-16: Ischnosoma acre (9-12; 9-10: holotype; 11-12: paratype), I. molle (13-14), and I. solodovnikovi (15-16): aedeagus in lateral and in ventral view. Scale bar: 0.2 mm.

Figs 17-25: Ischnosoma acre (17-19), I. molle (20-22), and I. solodovnikovi (23-25): (17, 20, 23) male sternite VII; (18, 21, 24) male sternite VIII; (19, 22, 25) postero-median portion of male sternite VIII. Scale bars: 17-18, 20-21, 23-24: 0.5 mm; 19, 22, 25: 0.2 mm.

Figs 26-31: Ischnosoma acre (26-27), I. molle (28-29), and I. solodovnikovi (30-31): (26, 28, 30) postero-median portion of male sternite VII; (27, 29, 31) close-up of postero-median portion of male sternite VII. Scale bars: 26, 28, 30: 0.2 mm; 27, 29, 31: 0.1 mm.