Encompassing an area of approx. 69.700 km², Georgia is characterized by a low degree of infrastructural development. With a population of about 3.7 million, it has a relatively low population density of about 53 people per km²; slightly more than 40% of the labor force works in agriculture (Redaktionsteam Weltalmanach 2018). Soils, vegetation, and climate zones are highly diverse and span semi-deserts and steppes in the southeast of Georgia, the subnival and nival-glacial levels of the Greater Caucasus, as well as the subtropical region of Colchis in the west with mild winters and high precipitation. Figure 1 gives an overview of the sampling localities within Georgia. A brief description of the localities is presented in Table 1 (a few of them are shown in Fig. 2). Areas with collecting localities were ecologically characterized using the typology of Nikolaishvili (2018), who, based on climate and vegetation, defines 20 landscape units for Georgia (see also Suppl. material 2).

Figure 1. 

Map of Georgia depicting the collecting localities (red dots) during the fieldwork in winter 2019.

The excursion took place from December 9 to December 19 in 2019, during which collections were made by the authors. Mostly, parts of bark or moss at the base of the trunks and in the lower trunk area (mostly up to a height of 1 or 1.5 m) were loosened and examined for ground beetles sitting underneath or between layers of bark. The capture of the animals was facilitated by the use of insect aspirators. In some cases, larger detached pieces of bark and moss were additionally searched on a white cloth, sometimes assisted by the use of a beetle sieve. At the base of the trunk, the soil substrate and litter lying close to the trunk were also searched and, in some cases, sifted through.

Hand catching and sieving were also conducted in some other habitat types (e.g. with reed beds, lying and standing dead wood, or grassland/forest ecotone). In the case of deadwood, this was dissected as much as possible in order to search inside for any hibernating individuals.

The survey was not standardized (i.e. by plot size or collecting time). However, at least one hour was spent collecting by two people at each location.

Genital preparations were made for most species. The aedeagus was removed from the animal and transferred into 70% ethanol. Any adhering tissue and skin residue were cleaned away, and the paramers were severed. The prepared aedeagus and the paramers were then transferred into a small plastic tube containing 10% potassium hydroxide solution, tightly sealed, and macerated in a water bath at just below 100°C for three to twenty minutes (depending on size). The aedeagus was then transferred to a small bowl with 10% acetic acid (to neutralize the alkaline solution) for five hours, followed by another five hours in a small bowl with water (to wash out the acid). The genitalia were finally embedded in a water-soluble medium (Polyvinylpyrrolidon) (Lompe 1989) on a transparent label (hygrophilic-coated inkjet printing foil). The paramers were glued to the same label.

Photographs of the adult insects and the aedeagi were made with stacking equipment from the State Museum for Natural History Stuttgart and the Ecological Station of Wuerzburg University in Fabrikschleichach.

The specimens were identified using Reitter (1887, 1905), Arndt et al. (2011), Retezár (2015), and reference material from the private collections of J. Trautner and M. A. Fritze. Specimens are deposited in the aforementioned collections of these authors. Some material will be transferred later to Ilia State University (Tbilisi). The nomenclature follows Lorenz (2005), updated by information from the current Palaearctic Checklist (Löbl and Löbl 2017).

At a total of 22 of 28 investigated localities, 227 specimens were recorded, and 43 taxa were identified at the species or subspecies level (Suppl. material 1). For two further taxa, a final determination is still pending; they are thus not considered here.

Two species, Dromius agilis (66 specimens at five sites) and D. semiplagiatus Reitter, 1887 (33 specimens at seven sites), were represented with the highest density underneath or between layers of bark. The number of specimens detected increased with increasing elevation, from 1050 to 1810 meters. D. agilis seems to prefer cooler and moister conditions than D. semiplagiatus and occurs in higher abundance even at low elevations when conditions are favorable (Site 18; Fig. 2A). In contrast, at sun-exposed sites with low tree canopy cover (site 15; Fig. 2B), D. semiplagiatus is more abundant.

Other species represented by several specimens were: Carabus varians varians and C. varians armeniacus Mannerheim, 1830 (17 specimens in single cells under loose bark of lying and standing dead logs at four sites; Fig. 2C); Morion olympicus L. Redtenbacher, 1843 (6 specimens); and Tachyta nana (9 specimens), each in a group about five cm deep in rotten wood in Lagodekhi National Park (Fig. 2D). Syntomus truncatellus (Linnaeus, 1760) (19 specimens) and Olisthopus sturmii (13 specimens) were most abundant in a grassland site (sieved samples) adjacent to herb fringe structures in the mountains near Bakuriani (site 17b; Fig. 2E). Noteworthy is the record of 10 Microlestes specimens from five species, three of them new for Georgia, in a dry steppe-like grassland site at Lake Jvari, northwest of Tbilisi (site 2; Fig. 2F).

Twenty-three species could only be recorded with a single specimen, and 32 species were recorded at only one site. Only parts of dead specimens of Calosoma maderae dsungaricum Gebler (1833) and Taphoxenus cellarum cellarum (M. Adams, 1817) were recorded under stones at Lake Kumisi. No ground beetles were detected at sites 1, 5, 9c, 10, 17c, or 20.

Figure 2. 

A: Habitat of Dromius agilis in Borjomi-Kharagauli National Park, site 18; B: Habitat of Dromius semiplagiatus near Bakuriani Andeziti, site 15; C: Carabus varians Fischer von Waldheim, 1823 in its winter quarter; D: Winter quarter and collecting site of Tachyta nana (Gyllenhal, 1810); E: Collecting site of Olisthopus sturmii (Duftschmid, 1812), Lebia cruxminor (Linnaeus, 1758) and other species (by sieving); F: Collecting site (image foreground) of 5 Microlestes species (by sieving).

The distribution status of the species was reviewed based on the work of Kryzhanovskij et al. (1995), Reck and Chaladze (2004), Löbl and Löbl (2017), and Anichtchenko (2019). Nine species were found to be new to Georgia. They are listed in alphabetical order.

Demetrias (Aetophorus) imperialis (Germar, 1823)

Turano-European species also occur in parts of northern Africa but are mostly absent in northern Europe (Müller-Motzfeld 2006; Trautner 2017). The species has been recorded in the Greater Caucasus (Kryzhanovskij et al. 1995), but was subsequently not mentioned for Georgia by either Reck and Chaladze (2004) or Löbl and Löbl (2017). The latter lists this species for the adjacent countries of Azerbaijan, southern European Russia, and Turkey. We found the species at a single location, a shallow siltation zone with a well-structured (nevertheless pronounced only over a small area) reed bed of lake Bazaleti southeast of Chanadirtkari (Site 4; Fig. 9B; Mzcheta-Mtianeti, landscape type 8 according to Nikolaishvili (2018), belonging to group "moderatly warm and semiarid"). One specimen is deposited in the collection of J. Trautner (Fig. 3).

Figure 3. 

Dorsal view of Demetrias imperialis (scale bar = 1mm).

Dromius (s. str.) agilis (Fabricius, 1787)

European and Sibirian-distributed species (Müller-Motzfeld 2006; Löbl and Löbl 2017). Löbl and Löbl (2017) list this species for the adjacent countries of Russia (Southern European Territory) and Turkey. The determination is based on the aedeagus illustrated in Müller-Motzfeld (2006). The coloration of the individuals found is different from that of most central European specimens; rather, they are monochromatic red-brown to brown individuals. They are rich in contrast, comparable to the taxon described as Dromius caucasicus by Semenov (1900), later synonymized with D. agilis. According to our observations thus far, the species is found at altitudes above 1200 m a.s.l. and exclusively on conifers (Caucasian Fir, pine, and spruce). We found the species at five locations (Site 6, 15, 17a, 18, 26 Mzcheta-Mtianeti, Samtskhe-Javakheti, landscape, landscape type 11, 12, 13 according to Nikolaishvili (2018), belonging to the group "moderatly warm and moderately cold and humid"). Thirty-four specimens are deposited in the collection of J. Trautner, and 23 specimens are in the collection of M.A. Fritze (Fig. 4A,B).

Figure 4. 

A: Dorsal view of Dromius agilis (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 0.5 mm).

Microlestes corticalis (L. Dufour, 1820)

Western Palaearctic species (Müller-Motzfeld 2006). The species has been recorded in the Greater Caucasus (Kryzhanovskij et al. 1995), but was subsequently not mentioned for Georgia by either Reck and Chaladze (2004) or Löbl and Löbl (2017). The latter lists this species for the adjacent countries of Russia (Southern European Territory) and Turkey. Determination is based on characteristics of the aedeagus and of the last genital sternum, which exhibit a half-moon-shaped indent with yellow hairs in front of the posterior edge (see Arndt et al. 2011). We found the species at a single location adjacent to Lake Kumisi, vegetated with reeds and tamarisk bushes (Site 8, Mzcheta-Mtianeti, landscape type 9, according to Nikolaishvili (2018), belonging to the group "moderatly warm and semiarid"). One specimen was deposited in the collection of J. Trautner (Fig. 5A,B).

Figure 5. 

A: Dorsal view of Microlestes corticalis (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 0.2 mm); C: Genital sternit (scale bar = 0.5 mm).

Microlestes fissuralis (Reitter, 1901)

Southeastern European to Central Siberian distribution (Müller-Motzfeld 2006). Löbl and Löbl (2017) list this species for the adjacent countries of Russia (Southern European Territory) and Turkey. The determination is based on the characteristically shaped aedeagus, with its receding hook on the underside of the tip (see Arndt et al. 2011). We found the species at a single location, dry grassland in the surroundings of the salt lake at Jvari Monastery, northeast of Tbilisi (Site 2; Fig. 2F; landscape type 8 according to Nikolaishvili (2018), belonging to group "moderatly warm and semiarid"). Two specimens were deposited in the collection of J. Trautner (Fig. 6A,B).

Figure 6. 

A: Dorsal view of Microlestes fissuralis (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 0.2 mm).

Microlestes fulvibasis (Reitter, 1901)

Western and Southern European, Pamiric-distributed species (Müller-Motzfeld 2006). Löbl and Löbl (2017) list this species for the adjacent countries of Azerbaijan, Russia (Southern European Territory), and Turkey. The determination is based on the aedeagus illustrated in Arndt et al. (2011). Sympatric with M. fissuralis. One specimen was deposited in the collection of J. Trautner (Fig. 7A,B).

Figure 7. 

A: Dorsal view of Microlestes fulvibasis (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 0.2 mm).

Microlestes luctuosus luctuosus Holdhaus in Apfelbeck, 1904

Southern European, Pamiric-distributed species are also found in North Africa. It has been recorded in the Greater Caucasus (Kryzhanovskij et al. 1995), but was subsequently not mentioned for Georgia by either Reck and Chaladze (2004) or Löbl and Löbl (2017). Latter lists this species for the adjacent countries of Armenia, Azerbaijan, Russia (Southern European Territory), and Turkey (Löbl and Löbl 2017). The determination is based on the aedeagus illustrated in Arndt et al. (2011). Same location as M. fissuralis. One specimen was deposited in the collection of J. Trautner (Fig. 8A,B).

Figure 8. 

A: Dorsal view of Microlestes luctuosus luctuosus (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 0.2 mm).

Paradromius (s. str.) suturalis (Motschulsky, 1844)

Transpalaearctic-distributed Eastern Palaearctic species reach Europe in Bulgaria, Greece, and the Southern Russian Plain (Khobrakova et al. 2014; Löbl and Löbl, 2017). There are only a few papers dealing with this species, mostly with a faunistic background (e. g. Lutshnik 1934; Hieke and Wrase 1988; Wrase 1991; Dudko et al. 2018). Therefore, only a little, rather vague, information on its ecology and habitat selection is known. Findings from river floodplains are reported (Khobrakova et al. 2014). Shilenkov (2010) summarized the species within a group of ground beetles living in coastal and wetland areas and highlighted marshes and shores of standing water as habitat. In contrast, Kodzhabashev and Penev (2006) name mesophilous to xerothermophilous forests as habitats, where the species occurs in leaf litter and on bark. Teofilova (2019) lists sparse vegetation and sand as habitat features. We found the species sympatric with Demetrias imperialis at a shallow siltation zone with a well-structured (nevertheless pronounced only over a small area) reed belt of lake Bazaleti southeast of Chanadirtkari (Site 4; Fig. 9B; landscape type 8 according to Nikolaishvili (2018), belonging to group "moderately warm and semiarid"). One specimen was deposited in the collection of J. Trautner (Fig. 9A).

Figure 9. 

A: Dorsal view of Paradromius suturalis (scale bar = 1 mm); B: Habitat of P. suturalis at Lake Bazaleti.

Pterostichus (Argutor) leonisi Apfelbeck, 1904

Southeast European, Anatolian-distributed species (Müller-Motzfeld 2006). Löbl and Löbl (2017) list this species for the adjacent countries of Russia (Southern European Territory) and Turkey. The determination is based on the aedeagus illustrated in Arndt et al. (2011). Same location as Demetrias imperialis and Paradromius suturalis (Site 4; Fig. 9B; landscape type 8 according to Nikolaishvili (2018), belonging to group "moderately warm and semiarid"). One specimen was deposited in the collection of J. Trautner (Fig. 10A,B).

Figure 10. 

A: Dorsal view of Pterostichus leonisi (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 1 mm).

Pterostichus (Phonias) strenuus (Panzer, 1796)

European, Sibirian-distributed species (Müller-Motzfeld 2006). Löbl and Löbl (2017) list this species for the adjacent countries of Russia (Southern European Territory) and Turkey. We found the species at a single location, a stand of pine trees on the pass northwest of Surami (Site 14, Shida Kartli, landscape type 11, according to Nikolaishvili (2018), belonging to the group "moderatly warm and moderately cold and humid"). One specimen was deposited in the collection of J. Trautner (Fig. 11A,B).

Figure 11. 

A: Dorsal view of Pterostichus strenuus (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 1 mm).

According to Fritze and Trautner (2017), mating and oviposition of Callistus lunatus (Fabricius, 1775) in Central Europe occur mainly in spring, followed by larval development in summer. According to the carabids.org database (Homburg et al. 2014; status 2021), it should not be known yet which stage overwinters. However, according to Wradatsch (1912), the species had already been captured as an imago in winter. The finding presently made in rotten wood of a lying dead tree trunk in the Alasani floodplain south of Heretiskari (site 21) is possibly the second, or in any case, one of the few documented cases known so far.

Winter captures are well suited to detect arboricolous species, for example, the genus Dromius. After their activity and reproduction phase during the vegetation period, individuals of these species often aggregate at the base of the trunk, hibernate there under moss and between bark scales, and can thus be easily recorded (e. g. Trautner 1984; Simon 2001). D. agilis was recorded for the first time during the present excursion, while D. semiplagiatus was already known from Georgia (Fig. 12A,B). Both species relying exclusively on conifers. Deciduous trees in the area, however, cannot be excluded per se as habitat for arboricolous Dromius species, despite the fact that no specimens were found during this work. Further investigations are necessary, possibly with the use of trapping systems as successfully used in the Netherlands (see Felix and Wielink 2008).

Figure 12. 

A: Dorsal view of Dromius semiplagiatus (scale bar = 1 mm); B: Lateral view of the median lobe of aedeagus (scale bar = 0.5 mm).

Furthermore, the importance of winter capture is also evident for species that belong to the "plant climbers", e.g. on reeds, sedges, or other grassy and herbaceous plants (as Paradromius and Demetrias species); or that use grass stands and grassy litter as essential structures of their habitat and aggregate there according to experience (e.g. Syntomus and Microlestes species).

In total, the following genera of our winter records are classified as arboricolous, plant-climbing, or "grass-stand-affinitive", and thus almost half (20) of all species detected during the winter excursion (number of species if >1 in parentheses): Demetrias, Dromius (2), Drypta, Lebia (2), Microlestes (7), Panagaeus, Paradromius (2), Philorhizus, and Syntomus (3). Among them, the majority of species are newly reported for Georgia.

The largest number of individuals located were recognizably in their winter quarters, respectively, in hibernation. However, some species are known to be active in the winter, at least under particularly favorable conditions. To them belong especially Trechus quadristriatus (Schrank, 1781) and Paradromius linearis (Olivier, 1795). The individual of Lebia cyanocephala (Linnaeus, 1758) found was sitting directly on dry grass under a flat stone and may have been active for a short time before the capture event.

The results also underline the relevance of different investigation or collection methods and recording periods for faunistic studies on ground beetles, especially a "looking over the edge of a ground trap" approach. Method combinations are recommended in practical nature conservation and environmental planning as well as in the field of research (e.g. Trautner 1992; Timm et al. 2008).

Interrupted by the pandemic situation in 2020, 2021, and 2022, surveys on the Georgian ground beetle fauna are to be resumed from 2023 onwards, with further field trips in the winter also planned.