Geostiba (Sibiota) immutata, Assing, 2017

Assing, Volker, 2017, On the Geostiba fauna of Armenia (Coleoptera: Staphylinidae: Aleocharinae), Linzer biologische Beiträge 49 (2), pp. 1075-1092 : 1087-1089

Geostiba (Sibiota) immutata nov.sp. ( Figs 50-58 , Map 3 )

T y p e m a t e r i a l: Holotype 3: " ARMENIA [49b] – SW Goris, ESE Tatev, 39°21'47''N, 46°16'52''E, 1950 m, forest margin, 14.VII.2017, V. Assing / Holotypus 3 Geostiba immutata sp. n. det. V. Assing 2017 " (cAss) . Paratypes: 233, 5 ♀♀: same data as holotype (cAss) ; 9♀♀: " ARMENIA [49] – SW Goris, ESE Tatev, 39°21'47''N, 46°16'52''E 1950 m, forest margin, 13.VII.2017, V. Assing " (cAss) ; 1♀: same data, but leg. Schülke (MNB) .

E t y m o l o g y: The specific epithet (Latin, adjective: unmodified) alludes to the absence of carinae or tubercles on the male sternite VII.

D e s c r i p t i o n: Body length 2.0-2.7 mm; length of forebody 0.9-1.0 mm. Coloration: body yellowish-brown to pale reddish-brown. Eyes small, with pigmentation, and composed of approximately five ommatidia. Pronotum without longitudinal impression on either side of midline. Hind wings completely reduced.

3: elytra ( Fig. 50 ) without sutural carina, with or without some granules along suture; abdominal tergite VII without modifications; posterior margins of tergite and sternite VIII broadly and weakly convex; median lobe of aedeagus ( Figs 51-54 ) 0.24-0.25 mm long, without distinct semi-transparent spines in internal sac; ventral process weakly curved in lateral view; paramere not distinctive.

♀: elytra without modifications; tergite VIII shaped as in male; posterior margin of sternite VIII ( Fig. 55 ) broadly and weakly convex, in the middle usually truncate to very shallowly concave; spermathecal capsule ( Figs 56-58 ) with undilated distal portion and short and twisted proximal portion.

C o m m e n t: The elytra are modified (with granules near suture) only in one of the three males. Since only three males are available, the possibility that there may be males with more pronounced elytral modifications, possibly even with modifications on the abdominal tergite VII, cannot be ruled out.

Based on the similar primary sexual characters, G. immutata is clearly closely allied to the other Armenian Sibiota species, suggesting that the absence of carinae or tubercles on the male tergite VII is a secondary reduction. Consequently, the species is attributed to the subgenus Sibiota and not to Sipalotricha SCHEERPELTZ, 1931.

C o m p a r a t i v e n o t e s: Geostiba immutata is readily distinguished from other Armenian Sibiota species by the absence of sutural carinae on the male elytra, by the unmodified male tergite VII, and by the shape of the spermatheca.

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 in the northeastern part of the Barkushati range, to the southeast of Tatev and approximately 18 km south of Goris ( Map 3 ). The specimens were sifted from litter and roots in a deciduous forest composed of oak, hornbeam, and maple at an altitude of 1950 m.

Figures

Map 3: Distribution of Sibiota species in Armenia: G. pambakica (white circles); G. tigrani (black circles); G. unicuneata (white diamonds), G. immutata (black star), G. meghruica (white triangles); G. sp. 1 (black triangle); G. sp. 2 (white star).

Figs 50-58: Geostiba immutata: (50) male elytra; (51-54) median lobe of aedeagus in lateral and in ventral view; (55) female sternite VIII; (56-58) spermatheca. Scale bars: 50: 0.2 mm; 51-58: 0.1 mm.