Geostiba (Sibiota) deliqua, Assing, 2018

Assing, Volker, 2018, A revision of Geostiba of the West Palaearctic region. XXVI. New species and additional records, primarily from the Caucasus region (Coleoptera: Staphylinidae: Aleocharinae), Linzer biologische Beiträge 50 (2), pp. 1033-1054 : 1043-1047

Geostiba (Sibiota) deliqua nov.sp. ( Figs 36-42 , 44 ; Map 2 )

T y p e m a t e r i a l: Holotype ♂: " ARMENIA [27] – WSW Kapan , W Kajaran, 39°09'22''N, 46°06'13''E 2050 m, mixed forest, 10.VII.2018, V. Assing / Holotypus ♂ Geostiba deliqua sp. n. det. V. Assing 2018" (cAss) . Paratypes: 2♂♂: same data as holotype (cAss) ; 1♀: same data, but leg. Schülke ( MNB) .

E t y m o l o g y: The specific epithet (Latin, adjective: missing, absent) alludes to the unmodified male tergite VII.

D e s c r i p t i o n: Body length 2.2-2.3 mm; length of forebody 0.8-0.9 mm. Habitus as in Fig. 36 . Coloration: body yellowish to reddish-yellow with the middle of abdominal segment VI slightly darker; legs and antennae pale-yellow. Eyes strongly reduced, composed of 3-4 ommatidia and with weak pigmentation ( Fig. 37 ). Other external characters not distinctive.

♂: elytra ( Fig 37 ) extensively and moderately deeply impressed, suture distinctly and broadly elevated near scutellum, posteriorly extending into a narrow keel; tergite VII unmodified, without tubercles or keel; median lobe of aedeagus 0.23 mm long and shaped as in Figs 38-41 .

♀: spermatheca as in Fig. 42.

C o m p a r a t i v e n o t e s: This species is distinguished from most other Armeni- an representatives of the subgenus Sibiota by small body size, pale coloration, and particularly by the unmodified male tergite VII. Using the key in ASSING (2017a), G. deliqua would key out at couplet 3, together with G. immutata ASSING, 2017 from the environs of Tatev (south of Goris), the only other Armenian Sibiota species without tubercles or keels on the male tergite VII. The new species differs from G. immutata by even smaller size, on average paler coloration, even smaller eye rudiments with fewer ommatidia (G. immutata: eyes composed of approximately 6 ommatidia), much more distinctly modified male elytra (G. immutata: without impressions; suture not elevated, with few granules on either side at most), by the shape of the smaller median lobe of the aedeagus (G. immutata: median lobe 0.24-0.25 mm long; ventral process more strongly curved in lateral view; crista apicalis smaller), and by the shape of the spermatheca.

Geostiba deliqua is evidently very closely allied to G. unicuneata , as can be inferred from the highly similar external characters (coloration, body size, eye size), from the similar modifications of the male elytra, the similar structure of the aedeagus, and from the similar shape of the spermatheca. Aside from the complete absence of the median keel on the male tergite VII, G. deliqua is distinguished from G. unicuneata only by a slightly larger median lobe of the aedeagus ( G. unicuneata : median lobe usually 0.21- 0.22 mm long) with the apex of the ventral process of slightly different shape and with an on average slightly larger crista apicalis. Despite the similarity of the primary sexual characters, it seems rather unlikely that G. deliqua is conspecific with G. unicuneata . First, the primary sexual characters are generally rather uniform in Armenian Sibiota ; for instance, the spermathecae of G. nigrohortensia and G. unicuneata are of practically identical shape, although these species are readily distinguished based on external characters alone. Second, the 36 males of G. unicuneata that have been examined so far have the median keel on tergite VII at least indicated, whereas this keel is completely absent in all three males of G. deliqua . Third, in males of G. unicuneata with a median keel of reduced size the elytral modifications are usually reduced, too. Finally, the slight differences in the shape of the apex of the ventral process of the aedeagus appear to be constant.

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 near Kajaran, west-southwest of Kapan, South Armenia ( Map 2 ), at an altitude of 2050 m. The type specimens were sifted from litter and grass roots in a montane mixed deciduous forest ( Fig. 44 ).

Figures

Map 2: Distributions of Geostiba unicuneata (black circles), G. deliqua (white circle), and G. meghruica (black diamonds).

Figs 36-42: Geostiba deliqua nov.sp.: (36) male habitus; (37) male forebody; (38-41) median lobe of aedeagus in lateral and in ventral view; (42) spermatheca. Scale bars: 36: 1.0 mm; 37: 0.2 mm; 38-42: 0.1 mm.

Figs 43-44: Type localities of Geostiba nigrohortensia nov.sp. (above) and G. deliqua nov.sp. (below).