Geostiba (Sibiota) kakhetiana, Assing, 2019

Assing, Volker, 2019, A revision of Geostiba of the West Palaearctic region. XXVII. New species from Georgia and Kyrgyzstan, and additional records (Coleoptera, Staphylinidae, Aleocharinae), Linzer biologische Beiträge 51 (2), pp. 717-730 : 726-727

Geostiba (Sibiota) kakhetiana nov.sp. ( Figs 13-23 )

T y p e m a t e r i a l: Holotype ♂: "N 42°14'27 E 45°29'42, GG Kakheti Lechuri N, 1510 m, 9.5.2019, Brachat & Meybohm (1) / Holotypus ♂ Geostiba kakhetiana sp. n. det. V. Assing 2019" (cAss). Paratypes: 3♂♂, 20♀♀: same data as holotype (cAss).

E t y m o l o g y: The specific epithet (adjective) is derived from Kakheti, the region where the type locality is situated.

D e s c r i p t i o n: Body length 2.1-2.8 mm; length of forebody 0.8-1.1 mm. Habitus as in Fig. 13 . Coloration: body reddish with yellow legs. Eyes weakly pigmented and composed of approximately 5-8 ommatidia. External characters ( Figs 13-14 ) as in other species of the G. carinicollis group, except as follows:

♂: elytra ( Fig. 14 ) shallowly impressed and with pronounced sutural carinae, these carinae broader and somewhat tuberculose in anterior half, sharp and narrow in posterior half; tergite VII ( Fig. 15 ) with a relatively small, but distinct median tubercle at posterior margin; tergite VIII ( Fig. 16 ) truncate or weakly concave in the middle; sternite VIII ( Fig. 17 ) with convex posterior margin; median lobe of aedeagus ( Figs 18-20 ) 0.27 mm long, with pronounced crista apicalis and with a short flagellum and 4-6 moderately sclerotized spines in internal sac.

♀: elytra shallowly impressed, these impressions less extensive than in male; tergite VIII of similar shape as in male; sternite VIII with weakly convex posterior margin, marginal setae weakly modified and rather long; spermatheca as in Figs 21-23.

I n t r a s p e c i f i c v a r i a t i o n: In one of the males, the sutural carinae are significantly less pronounced and the tubercle on tergite VII is practically obsolete.

C o m p a r a t i v e n o t e s: Geostiba kakhetiana is most easily distinguished from all other representatives of the G. carinicollis group recorded from Georgia and from the Greater Caucasus by the small median tubercle at the posterior margin of the male tergite VIII. In addition, it is characterized by the shapes of the median lobe of the aedeagus and of the spermatheca. The only other species of the G. carinicollis group with one median elevation (not a pair of carinae) on the male tergite VIII known from the Great Caucasus is G. uniplicata ASSING, 2011 from the environs of Krasnaya Polyana in the West Caucasus. In this species, however, the median elevation is much longer and distinctly oblong.

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 locality is situated to the north of Telavi, East Georgia, in the southern slopes of the Greater Caucasus. The specimens were sifted from leaf litter in a stream valley with deciduous forest at an altitude of 1510 m. The sex ratio appears to be biased in favour of females: only four out of 24 specimens are males.

Figures

Figs 8-14: Geostiba zerchei (8-12) and G. kakhetiana (13-14): (8, 13) male habitus; (9, 14) male forebody; (10-11) median lobe of aedeagus in lateral and in ventral view; (12) spermatheca. Scale bars: 8, 13: 1.0 mm; 9, 14: 0.5 mm; 10-12: 0.1 mm.

Figs 15-23: Geostiba kakhetiana: (15) male abdominal segments VI-VIII; (16) male tergite VIII; (17) male sternite VIII; (18-20) median lobe of aedeagus in lateral and in ventral view; (21-23) spermatheca. Scale bars: 15: 0.5 mm; 16-17: 0.2 mm; 18-23: 0.1 mm.