The first records of the genus Tychobythinus Ganglbauer, 1896 from Georgia (Coleoptera: Staphylinidae: Pselaphinae)

Three microphthalmous and presumably locally endemic species of Tychobythinus Ganglbauer, 1896, a pselaphine genus previously unknown from Georgia, are described and illustrated: T. meskheticus spec. nov. (Southwest Georgia: Meskheti Range), T. eximius spec. nov. (Northwest Georgia: Egrisi Range), and T. egrisicus spec. nov. (Northwest Georgia: Egrisi Range). Tychobythinus eximius is particularly remarkable in that it is subject to a unique sexual dimorphism of the antennae and the pronotum. Including the new species, Tychobythinus is now represented in the Palaearctic region by 95 named species and two subspecies.


Introduction
According to Schülke & Smetana (2015), the Holarctic genus Tychobythinus Ganglbauer, 1896 was represented in the Palaearctic region by 86 species (plus two subspecies), four of them confined to the East Palaeartic (Japan, China, Taiwan) and the remainder distributed in the West Palaearctic region. In the meantime, six additional species have been described from Greece, Italy, and Turkey (Brachat 2019, Hlaváč & Faille 2018, Poggi 2019, Poggi & Magrini 2015, Sabella et al. 2019, 2020. Only four species were previously known from the Caucasus region sensu lato: T. caviceps (Reitter, 1881) (Azerbaijan, Iran), T. clermonti (Jeannel, 1950) (Russian West Caucasus), T. loebli Hlaváč & Faille, 2018 (Northeast Turkey: Trabzon), and T. repens Kurbatov, 2006 (Russian West Caucasus) (Kurbatov 2006). The genus had never been reported from Georgia. Some Tychobythinus species have strongly reduced eyes and are found by extracting deep litter layers and soil by sifting or soil-washing; several microphthalmous species have exclusively been collected in caves. While the ventral side of the head is generally sexually dimorphic in Tychobythinus species, a sexual dimorphism of the antennae had been observed only in the two species from the Krasnodar region in the Russian West Caucasus (T. clermonti, T. repens). A pronounced sexual dimorphism of the pronotum was previously unknown in the genus. Ten field trips conducted to Georgia conducted by Heinrich Meybohm (Großhansdorf), Michael Schülke (Berlin), and the authors since 2015 yielded a total of 28 specimens of Tychobythinus. Examination of this material revealed that it is composed of probably six undescribed species, three of which are represented exclusively by females. The three species of which males are available, all of them microphthalmous and most likely locally endemic, are described in the present study. One of them is characterised by unique modifications of the male antennae and the male pronotum.

Material and methods
The material treated in this study is deposited in the following collections: cAss Private collection Volker Assing, Hannover cBra Private collection Volker Brachat, Geretsried MNB Museum für Naturkunde, Berlin (coll. Schülke) The morphological studies were conducted using Stemi SV 6 (Zeiss) and Discovery V12 (Zeiss) microscopes, and a Jenalab compound microscope (Carl Zeiss Jena). The images were created using digital cameras (Axiocam ERc 5s, Nikon Coolpix 995), as well as Labscope and Picolay software. The map was created using MapCreator 2.0 (primap) software. Body length was measured from the anterior margin of the labrum to the apex of the abdomen, the length of the aedeagus from the apices of the parameres to the base of the aedeagal capsule. Other measurements are abbreviated as follows: HL -head length from the anterior margin of the frons to the posterior constriction of the head; HW -head width across and including eyes; PpL -length of maxillary palpomere IV; PL -length of pronotum; EL -length of elytra along suture; EW -maximal width of both elytra combined. The "parameral" side (i.e., the side where the sperm duct enters) is referred to as the ventral, the opposite side as the dorsal aspect. Morphological terminology mostly follows Chandler (2001).

Descriptions of new species
Tychobythinus meskheticus spec. nov.

Description: Habitus as in
Comparative notes: Tychobythinus meskheticus is distinguished from its geographically closest congeners T. clermonti, T. repens (Russian West Caucasus: Krasnodar region), and T. loebli (Northeast Turkey: Trabzon) by different modifications of the antennae and the structure of the aedeagus. For illustrations of the aedeagi of the compared species see Kurbatov (2006) and Hlaváč & Faille (2018).

Etymology:
The specific epithet (Latin, adjective: extraordinary, exceptional) alludes to the unique sexual dimorphism of the pronotum and the antennae.
Comparative notes: Tychobythinus eximius is readily distinguished from all other species of the genus by the conspicuous modifications of the male antennae, a uniquely modified male pronotum, and the structure of the aedeagus.
Distribution and natural history: The species was discovered in two close localities in the southern slopes of the Egrisi Range, Zemo Svaneti, Northwest Georgia (Map 1). The specimens were collected by sifting deep litter (two specimens) and soil-washing (four specimens) in a deciduous forest margin, mostly near large rocks (Fig. 13)

Etymology:
The specific epithet is an adjective derived from Egrisi, the name of the mountain range where the species was discovered. Fig. 7. Body length 1.3 mm. Body reddish-brown, with long and suberect pubescence. Head transverse (HL: 0.28 mm; HW: 0.31 mm), with scattered punctation; frontal lobe 0.15 mm broad; frontal sulcus broad. Eyes strongly reduced, composed of three minute and weakly defined ommatidia without pigmentation. Maxillary palpi long; palpomeres II and III with several fine tubercles; palpomere IV 0.20 mm long, slightly more than twice as long as broad. Pronotum laterally finely carinate, with scattered punctation on disc, near posterior margin more densely punctate. Elytra distinctly transverse (EL: 0.48 mm; EW: 0.71 mm), with fine and indistinct punctation. Abdomen 0.23 mm long. : head ventrally with a transverse impression, behind this impression with four very long and erect setae; antenna (Fig. 8) slender, 0.7 mm long, without evident modifications; antennomere I four times as long as broad (length 0.20 mm); aedeagus 0.24 mm long and shaped as in Fig. 13. : unknown.

Description: Habitus as in
Comparative notes: Tychobythinus egrisicus is distinguished from all its congeners by the morphology of the aedeagus, particularly the shapes of the internal structures. It additionally differs from the two other species described in this paper by unmodified male antennae, finer and sparser punctation of the forebody, a transverse head, and more strongly transverse elytra, and from the two species recorded from the Krasnodar region by unmodified antennae. Tychobythinus caviceps from Azerbaijan and Iran, with which the new species shares unmodified male antennae, is characterised by an aedeagus with internal structures of distinctive shapes (see illustration in Kurbatov 2006).

Distribution and natural history:
The type locality is identical to that of T. eximius. The holotype was collected by washing soil from a margin of a deciduous forest with predominant alder and hazelnut with rocks near a mountain track at an altitude of 580 m.