Checklist of hover flies (Diptera, Syrphidae) of the Republic of Georgia

Abstract A checklist of the Syrphidae species of the Republic of Georgia is presented. New hover fly (Diptera: Syrphidae) records from Georgia are provided as a result of field work conducted in 2018. At the same time, published syrphid records for the country are here reviewed and updated. A total of 357 species of hoverflies are now documented from Georgia, 40 of which are reported for the first time. Moreover, DNA barcodes were sequenced for 238 specimens, representing 74 species from this country.


Introduction
With an almost worldwide distribution, absent from Antarctica and remote oceanic islands, Syrphidae is a very species-rich family of Diptera with more than 6,000 described species (Brown 2009;Thompson 2019). Commonly called flower flies or hover flies, adults are associated with flowers that are used as mating sites and energy food sources (pollen and nectar). They are considered essential pollinators of wild flowering plants and crops (Pérez-Bañón et al. 2003a;Ssymank and Kearns 2009;Inouye et al. 2015) and have been used as bioindicators in order to evaluate biodiversity loss and the efficiency of restoration and conservation policies (Sommaggio 1999;Tscharntke et al. 2005;Biesmeijer et al. 2006;Ricarte et al. 2011;Sommaggio and Burgio 2014). Syrphid immatures have a large array of natural histories and are variable in structure and feeding modes (Rotheray 1993, Rotheray and Gilbert 1999. Some of these larvae play an important role as biological control agents of pests (Schmidt et al. 2004; Bergh and Short 2008;Bugg et al. 2008;Nelson et al. 2012;Eckberg et al. 2015) or as decomposers of organic matter (Lardé 1989;Martínez-Falcón et al. 2012), but some phytophagous larvae may be considered plant pests under certain circumstances (Edwards and Bevan 1951;Stuckenberg 1956;Tompsett 2002).
The Caucasus Region is situated between the Black Sea and the Caspian Sea ( Fig.  1) and is one of the global 'biodiversity hotspots' (Myers et al. 2000;Mittermeier et al. 2004;Zazanashvili et al. 2004). The region comprises the Republics of Armenia, Azerbaijan and Georgia (sometimes all together called Transcaucasia), parts of northwestern Turkey, northern Iran, and Russian republics and krais between the Sea of Azov and Black Sea on the west and the Caspian Sea on the east (area known as Ciscaucasia or Northern Caucasus). Georgia lies in the central part of the Caucasus Region and has two major mountainous ranges, i.e., the Greater Caucasus and the Lesser Caucasus.
Regarding species diversity, there is a geographic gap of knowledge in the Caucasus Region, especially on the dipteran fauna (Insecta: Diptera) (Wetzel et al. 2008;Oboňa et al. 2019). The hover fly fauna of Georgia has never been studied in detail. Previous works on the Syrphidae fauna of the Caucasus Region are predominantly done by Soviet authors, published mainly in Russian-language magazines, focusing in the fauna of the Northern Caucasus, although some include the fauna of Armenia and/or Azerbaijan (Portschinsky 1877;Zaitzev 1912;Paramonov 1926aParamonov , 1926bParamonov , 1927aParamonov , 1927bStackelberg 1926Stackelberg , 1960Stackelberg , 1968Zimina 1960Zimina , 1976Skufjin 1967Skufjin , 1976Stackelberg and Richter 1968;Tóth and Günther 1992;Barkalov 1993;Kustov 2006, among others). More recently, Hauser (1998) presented new records for Azerbaijan with the description of two new species. Regarding Georgian syrphid fauna,  and  were the only authors who explicitly stated that their studies were entirely conducted in Georgia, and  is the only work known to the authors with a clear focus to document the syrphid fauna of Georgia. In addition, there are two general bibliographic references for the Palaearctic with notes on the Caucasus Region. The first is , who in her catalogue of Palaearctic Diptera barely mentioned Georgia explicitly, but used very often the term Transcaucasia (TC). Since then, no other work treated the entire Palaearctic syrphid fauna. The second reference is , who focused on European species of hover flies.  is a compilation of published works with some personal comments, but includes the distribution of the species with mentions to the Caucasus Region. Since 2012, the Zoologisches Forschungsmuseum Alexander Koenig (ZFMK) has coordinated and led the project German Barcode of Life (GBOL; https://www. bolgermany.de/), an initiative to create a DNA barcode library (Hebert et al. 2003a(Hebert et al. , 2003b of the German animals, plants and fungi (Geiger et al. 2016). In 2017, the German Federal Ministry of Education and Research (BMBF) granted a proposal to set up a Georgian-German Biodiversity Center (GGBC) as a multinational approach to explore the biodiversity of the Caucasus area (grant number 01DK17048; project's website: https://ggbc.eu/). The experience of GBOL and its infrastructure is supposed to serve as a model for the development of a comparable structure in Georgia, together with other knowledge transfer and exchange of students and researchers between the ISU (Ilia State University, Tbilisi, Georgia) and the ZFMK (Thormann et al. 2019). A continuation of the GGBC is currently planned as a Georgian-Armenian-German initiative, the Caucasus Barcode of Life Platform (CaBOL) (see Thormann et al. 2019 for more details). In the present work, we report the results of a collection expedition between June and July of 2018, as part of the collaboration effort between the ISU and the ZFMK. Within the GGBC framework, we here provide the first DNA barcodes for the syrphid fauna of Georgia, a stepping-stone for ongoing (GGBC) and planned (CaBOL) projects.

Literature records
Authors used  as the primary source. In this publication, we registered all the species listed in the Transcaucasia (TC), i.e., south of the main ridge of the Caucasus, including Georgia, Armenia and Azerbaijan. Unless the country was explicitly indicated, we have listed to occur in Georgia all the TC species from  catalogue, and added a note when the species was explicitly listed from Georgia. Based on that keystone publication, we critically reviewed published literature up to date in order to find Georgian records. We assumed that  summarized other important works on the syrphid fauna of the Caucasus such as Stackelberg and Richter (1968) or , who provided the first Syrphidae records from the Borjomi area, in Lesser Caucasus. Nevertheless, we also studied  and Stackelberg and Richter (1968) in case some more precise locality details were mentioned in the original works.
In addition, we consulted the Georgian Biodiversity Database (http://biodiversity-georgia.net/index.php), which is a digital compilation of field observations and a summary of the work by , and two more general publications that somehow were updates of :  and . From , we incorporated species listed from Georgia or the Caucasus; while from , we included all the species listed as Transcaucasia (TC), although no Georgian records were explicitly given. If a species was listed as TC but no Georgian record was explicitly given, we indicate our records as the first ones for Georgia. Other more specific articles devoted to single taxa were all checked for Georgian records.
We did not study type material for species with uncertain taxonomic status. A revision of the taxonomic status of such species is beyond the scope of the present work. When appropriate, we have indicated such uncertainty under the species remarks. In the same line, we did not study the material reported from Georgia or Transcaucasia from other authors or published works. Nevertheless, we have indicated some remarks about the identification of previous published material.
For the current distribution of the listed species we used  as the most up-to-date reference, although other published works were consulted for specific taxa in order to obtain a more accurate distribution. We used three different categories in the current distribution with comments: 1) realms such as Palaearctic when the species has a very broad distribution; 2) regions such as Europe or Transcaucasia; and 3) countries, like Georgia, when the species is only known from those countries. For a more detailed geographic distribution, we refer to .
We need to point out that  has several systematic and nomenclatural errors. For the sake of traceability, we indicated such nomenclatural errors in the text with a [sic] (sic erat scriptum = thus was it written, intentionally so written).

New records
Field expedition took place between 15 June and 27 July 2018. Several Georgian provinces were visited (see Table 1) and all the specimens were collected using a handnet except where indicated. Specimens collected by Sander Bot are deposited in the Sander Bot's Personal Collection (SBPC; Haren, the Netherlands); specimens collected by André Reimann and Björn Rulik are deposited in the Senckenberg Museum für Tierkunde (MTD; Dresden, Germany) and in the Zoologisches Forschungsmuseum Alexander Koenig (ZFMK; Bonn, Germany); and specimens collected by Birthe Thormann, Jana Thormann, Benedikt Wipfler, David Tarkhnishvili, Jonas Astrin, Hans-Joachim Krammer, Marianne Espeland and Ximo Mengual are deposited in the Zoologisches Forschungsmuseum Alexander Koenig (ZFMK; Bonn, Germany). The flower flies of three malaise trap samples taken between 29 June and 14 July 2018 in the Kintrishi region as part of the GGBC project (Thormann et al. 2019) were sorted and studied by André Reimann and are also included in the present work. These specimens are deposited in the Zoologisches Forschungsmuseum Alexander Koenig (ZFMK; Bonn, Germany) and some duplicates are deposited in the Senckenberg Museum für Tierkunde (MTD; Dresden, Germany). In addition, material collected in Georgia by Jens-Hermann Stuke in 2001 and deposited at the ZFMK was studied by the first author and included as well.
A list of all the sampling localities with detailed information is given in Table 1 and illustrated in Fig. 1. Geographical coordinates were taken in the field and later corrected using Google Earth ®. SimpleMappr (Shorthouse 2010) was used to create Fig. 1. For the new records, the locality number is given following Table 1 and we indicate the number of specimens and sex and the unique identifier or number at the end. Specimens with unique identifiers starting with ZFMK-DIP or ZFMK-TIS are deposited in the ZFMK collections and are unique for each specimen, while identifiers starting with MTD denote single specimens or lots (group of specimens from the same collecting event) and are deposited in the MTD collections.
Specimens marked with an asterisk (*) are field observations only, so these fly/ flies have not been collected. No additional photographic material exists for these field observations.
For the author of the names published in Meigen (1822), the original work by Meigen was used. For the new species published in Meigen (1822), authorship was given to Hoffmannsegg when the abbreviation Hgg. appeared after the name; Megerle when abbreviation Meg. appeared after the name; Wiedemann when abbreviation Wied. appeared after the name; and to Meigen when no abbreviation was written after the name of the new species.

Molecular methods
DNA barcodes (Hebert et al. 2003a(Hebert et al. , 2003b were generated by following the standard protocols of the GBOL (German Barcode of Life) project (Geiger et al. 2016;http:// www.bolgermany.de). Total genomic DNA was isolated from one or two legs using the DNeasy Blood and Tissue Kit and the BioSprint96 magnetic bead extractor by Qiagen (Hilden, Germany). Remnants of specimens were preserved and labelled as DNA voucher specimens for the purpose of morphological studies and deposited at the ZFMK. Polymerase chain reaction (PCR) for the mitochondrial cytochrome c oxidase subunit 1 (COI) gene was carried out in total reaction mixes of 20 μl, including 2 μl of undiluted DNA template, 0.8 μl of each primer (10 pmol/μl), and standard amounts of the reagents provided with the 'Multiplex PCR' kit from Qiagen (Hilden, Germany). LCO1490-JJ [5'-CHACWAAYCATAAAGATATYGG-3'] and HCO2198-JJ [5'-AWACTTCVGGRTGVCC AAARAATCA-3'] (Astrin and Stüben 2008) were used as standard primers.
Thermal cycling was performed on Applied Biosystems 2720 Thermal Cyclers (Life Technologies, Carlsbad, CA, USA), using a PCR program with two cycle sets, as a combination of a 'touchdown' and a 'step-up' routine as follows: hot start Taq activation: 15 min at 95 °C ; first cycle set (15 repeats): 35 s denaturation at 94°C, 90 s annealing at 55°C (−1°C per cycle) and 90 s extension at 72°C; second cycle set (25 repeats): 35 s denaturation at 94°C, 90 s annealing at 40°C, and 90 s extension at 72°C; final elongation 10 min at 72 °C. Unpurified PCR products were subsequently sent for bidirectional Sanger sequencing to BGI (Hong Kong, China). The sequences were edited for base-calling errors and assembled using Geneious R7 (version 7.1.3, Biomatters Ltd.) and all new sequences were submitted to GenBank (see accession numbers under each species).
We compared the newly obtained DNA barcodes from Georgian specimens with COI sequences present in GenBank (https://www.ncbi.nlm.nih.gov/genbank/) and in BOLD systems (http://www.boldsystems.org/index.php). We provided the Barcode Index Number (BIN) (Ratnasingham and Hebert 2013) for the sequenced taxa and for their nearest neighbour in BOLD systems when they had a BIN.

Results
A total of 2,312 specimens were studied. We reported 357 different species belonging to 78 genera, with 40 species recorded from Georgia for the first time. Moreover, we were able to sequence DNA barcodes for 238 specimens (GenBank accession numbers for each species are provided under the section Genetics) representing 74 species from this country (see Suppl. material 1: Figure S1). The species are listed in alphabetic order. Reference.  as Cheilosia pseudogrossa Stackelberg, 1956 [sic]. Distribution. Transcaucasia. Remarks. Stackelberg (1968) described the species from the Northern Caucasus (Teberda, Teberdinsky State Natural Biosphere Reserve), and  reported it from Tsebelda (Abkhazia region). Distribution. Europe and Transcaucasia. Remarks. Reported from the Northern Caucasus by Barkalov (1993), and subsequently by . Reported for Georgia for the first time.

Cheilosia (Cheilosia) schnabli Becker, 1894
Reference. ;  as Cheilosia schnabli Becker, 1921 [sic];   Genetics. The GenBank accession numbers for the three sequenced specimens are MN621915, MN621916, MN621917. The BIN for these specimens is BOLD:ADX7783 and our sequences are very similar (98.62%) with the single previous record of this species in GenBank (LT707517 from Russia).
The year of publication for Cheilosia illustrata was a convention. The original work by Harris (1776-1780) was published in five 'decads' or parts.  used the conventional date of 1780? with a question mark for decads 3, 4, and 5 based on Lisney (1960). Evenhuis (1997: page 343) established that the decad 4, where Musca illustratus is described on page 104, was dated as 1779 based on the latest date of the plates. Thus, the year of publication should be 1779, i.e., Cheilosia illustrata (Harris, 1779).
Distribution. Germany, Northern Europe, Siberia, Mongolia to the Pacific. Remarks.  reported this species from Lagodekhi, Batsara canyon (Georgia), but this material was not available to our study. We think it would be necessary to compare the material from  with specimens from northern latitudes to confirm the presence of this taxon in Georgia. Genetics. We sequenced one specimen (MN621919) and its COI barcode has 99.18% similarity with a private sequence identified as Chrysotoxum intermedium Meigen, 1822.
Distribution. Western and Central Palaearctic into central Siberia.
Distribution. Europe, Turkey, European parts of Russia, and into Altai Mountains.

Remarks.
The year of publication for this species was a convention.  used the conventional dates based on Lisney (1960): 1776 for decad 1, 1776? for decad 2, and 1780? for decads 3, 4, and 5. Evenhuis (1997: page 342) found that the decad 2, where Musca cautus is described on page 60, was dated as 1778 in the "Discours préliminaires" to the Encyclopédie méthodique par ordre des matières -Insectes. Thus, the year of publication should be 1778.
Distribution. Palaearctic and northern India.

Distribution. Europe.
Remarks. The material from the Caucasus Region referred as C. intermedium needs re-examination to reassess its taxonomic identity as C. lessonae is reported here and the two species are very similar (see Speight 2018a). Genetics. We sequenced three specimens (MN621923, MN621924, MN621925); all with identical COI barcode. This species is not present in BOLD and we are providing the first COI sequences. The obtained sequences have a high similarity with sequences of Chrysotoxum intermedium (99.33%; BOLD:AAE9233).

Chrysotoxum lessonae
Distribution. Europe, Turkey and Iran Vujić et al. 2017). Remarks. Reported for Georgia for the first time.
Distribution. Holarctic and Indomalayan Region (northern India and Taiwan).
Distribution. Palaearctic. Remarks. Stackelberg and Richter (1968) stated that  recorded this species from Borjomi area. In the original publication,  did not list this species.
Distribution. Palaearctic. Remarks. Thompson et al. (1982) explained the application of the name Doros profuges to this taxon.
The year of publication for this species was a convention. The original work by Harris (1776-1780) was published in five 'decads' or parts.  used the conventional date of 1780? with a question mark for decads 3, 4, and 5 based on Lisney (1960). Evenhuis (1997: page 343) established that the decad 3, where Musca profuges is described on page 81, was dated as 1779 based on the latest date of the plates. Thus, the year of publication should be 1779.

Epistrophe eligans (Harris, 1779)
Reference. ; ;   Remarks. The year of publication for this species is a convention. The original work by Harris (1776-1780) was published in five 'decads' or parts.  used the conventional date of 1780? with a question mark for decads 3, 4, and 5 based on Lisney (1960). Evenhuis (1997: page 343) established that the decad 4, where Musca eligans is described on page 105, was dated as 1779 based on the latest date of the plates. Thus, the year of publication should be 1779. Remarks. Reported for Georgia for the first time.
Distribution. The geographic range of this species needs reassessment due to the confusion with related species Epistrophe melanostoma (Zetterstedt, 1943) and Epistrophe nitidicollis until recently (Doczkal and Schmid 1994).
Distribution. Palaearctic and Indomalayan Region. The records from the Indomalayan Region need confirmation due to the confusion with other morphologically similar Episyrphus species.  lists this species from Australia, but Wright and Skevington (2013) do not report it in their revision of the Australian species of Episyrphus.
Distribution. Palaearctic. Remarks. Portschinky (1892) described Eristalis alpinus var. caucasicus Portschinky, 1892 from the valley of the river Akstafa (also known as Aghstev) in Armenia and Azerbaijan. The taxonomic status of caucasica needs re-examination.
Distribution. Europe, European parts of Russia, Transcaucasia, and Turkey.
Distribution. Central and Southern Europe, Transcaucasia, Central Palaearctic to Mongolia.

Eumerus armenorum Stackelberg, 1960
Reference.  listed it only from Armenia;  listed it from Transcaucasia.
Remarks. There is not a specific record from Georgia. Distribution. Described from Armenia.

Eumerus caucasicus Stackelberg, 1952
Reference. Stackelberg (1952); Stackelberg (1961); ; . Distribution. Georgia. Remarks. This species was described based on a single male. We did not study the holotype, but our specimens fit the original description and key out to this species using the identification key by Stackelberg (1961). The females are identified as E. caucasicus based on the sampling event, plus we could not key them our properly using Stackelberg (1961). The studied specimens are the first records for this species since its original description. Moreover, this is the first report of a female of this species.
Distribution. Europe, European parts of Russia, and Crimea.
Distribution. Eastern Europe, Transcaucasia, and through Russia to Kamchatka.

Helophilus pendulus (Linnaeus, 1758)
Reference. ; . Genetics. We sequenced one specimen (MN621978) and its COI barcode has 100% similarity with other published sequences of this species. The Barcode Index Number Registry lists 1 BIN for this taxon (BOLD:AAI6747) with an average p-distance of 0.25% within BIN (1.65% max.) and a p-distance of 1.96% to the nearest neighbour in BOLD systems, Helophilus sapporensis Matsumura, 1911 (BOLD:ACO5411).

Leucozona (Leucozona) lucorum (Linnaeus, 1758)
Remarks. Since the morphological characters, which help to distinguish between L. lucorum and L. nigripila, have only recently been clarified by Doczkal (2000b), it is unclear whether L. lucorum occurs in sympatry with L. nigripila in the Caucasus or whether all records should refer to L. nigripila.
Distribution. Northern Caucasus and Transcaucasia.
Remarks. Here we have listed under L. nigripila all the previous records of L. lucorum. Since the morphological characters, which help to distinguish between L. lucorum and L. nigripila, have only recently been clarified by Doczkal (2000b), it is unclear if L. lucorum occurs in sympatry with L. nigripila in the Caucasus, but it is very unlikely. This species was described from Northern Caucasus (Circassia) and Doczkal (2000b) reported it from there and from Kussari (= Qusar, Azerbaijan). The specimen from Kussari is very likely to be the female that Mik (1888) mentioned from the Caucasus. Reported for Georgia for the first time.
Distribution. Central and Southern Europe, European parts of Russia, Transcaucasia, and Iran.
Distribution. Holarctic. Remarks. Haarto and Ståhls (2014) proved that different Melanostoma species share the same COI haplotypes among them and that this mitochondrial gene is not very useful for species identification.  mentioned the possibility of a species complex under this name because it has a large phenotypic variability and ecological amplitude.
Distribution. Palaearctic, eastern Afrotropics, and Indomalayan Region. Remarks.  cited this species "throughout the Oriental region to New Guinea", but Ramage et al. (2018) did not report it from Australasian and Oceanian Regions. Haarto and Ståhls (2014) proved that different Melanostoma species share the same COI haplotypes among them and that this mitochondrial gene is not very useful for species identification.
Remarks. This species was described from France but it has never been recorded again from this country. Other records were reported from Italy, Greece, and Israel (Speight 2018a) but some of these records need confirmation (Vujić et al. 2020). The last identification key where this species was included was done by Sack (1928)(1929)(1930)(1931)(1932). This species needs a redefinition/redescription to help distinguish it from other Merodon species .
Distribution. Europe, Transcaucasia, and North Africa, but needs reassessment.
Remarks. The Merodon aureus group comprises a number of different subgroups and species complexes (Veselić et al. 2017). All the identifications of this species are in need of verification to avoid confusion with other species of this complex. We follow Thompson (2019) and consider Merodon aeneus Megerle in Meigen, 1822 a junior synonym of Merodon aureus.
Distribution. Mediterranean Basin. Remarks. Merodon avidus is a species complex with taxonomic difficulties and a considerable morphological variability (Milankov et al. 2001(Milankov et al. , 2009Ståhls et al. 2009;Popović et al. 2015;. The color variability has been explained by the differential availability of trophic resources during the larval stage (Hurkmans 1993), but difficulties in distinguishing the species of this complex based on morphological characters remain. All the identifications of the species of this complex need verification.
Distribution. Balkan Peninsula and Transcaucasia. Paramonov, 1926 is now considered a junior synonym of M. caucasicus (proposed by Popov 2007; A. Vujić pers. comm. in Smit and Langeveld 2018). Merodon batumicus was described from Batumi area in Georgia (Paramonov 1926b) and reported for this country by  and .
Distribution. Mediterranean Basin, Crimea, and Transcaucasia. Remarks.  listed this species from Transcaucasia, but Speight (2018a) listed it only from Azerbaijan.
Distribution. Europe, European parts of Russia, and Transcaucasia.
Remarks. Reemer et al. (2005) suggested caution with records of this species from the Caucasus Region (see Stackelberg and Richter 1968) because the closely related species Myolepta mada Reemer and Hauser in Reemer, Hauser & Speight, 2005 may occur in this region, although it is currently known only from Azerbaijan.
The year of publication for this species is a convention. The original work by Harris (1776Harris ( -1780 was published in five 'decads' or parts.  used the conventional date of 1780? with a question mark for decads 3, 4, and 5 based on Lisney (1960). Evenhuis (1997: page 343) established that the decad 4, where Musca potens is described on page 110, was dated as 1779 based on the latest date of the plates. Thus, the year of publication should be 1779.
Distribution. Greece, Turkey, Azerbaijan, and Iran. Remarks. Reported for Georgia for the first time.

Distribution. Europe and Transcaucasia.
Remarks. Reemer et al. (2005) studied material from Azerbaijan, but no published record exists explicitly from Georgia.  listed the Far East (Khabarovsk and Primorye Territories) in the range of this species, but these records needs verification (Reemer et al. 2005).
The year of publication for this species is a convention. The original work by Harris (1776-1780) was published in five 'decads' or parts.  used the conventional date of 1780? with a question mark for decads 3, 4, and 5 based on Lisney (1960). Evenhuis (1997: page 343)  Remarks. Reported for Georgia for the first time.
Distribution. Palaearctic, but not in northern Africa. Kuznetzov, 1990 New Genetics. We were able to sequence two specimens of this taxon (MN622037, MN622038), which is not present in BOLD systems or GenBank. The two COI barcodes were identical between them and very similar to other Pipizella species (100% similarity with sequences of Pipizella annulata and 99.24% similar to P. zeneggenensis).

Pipizella nataliae
Distribution. Georgia and Turkey. Genetics. Three specimens (a male and two females) were sequenced (MN622039, MN622040, MN622041) and their COI barcodes differ from 0% to 0.61%. This species was not present in BOLD systems or GenBank, and our sequences are identical (100% similarity) to COI sequences of specimens identified as Pipizella pennina (Goeldlin de Tiefenau, 1974) and P. zeneggenensis.

Remarks.
We have assumed that the three collected females belong to this species based on the COI sequences and the co-occurrence with a male. Reported for Georgia for the first time. Remarks. The year of publication for this species is a convention. The original work by Harris (1776-1780) was published in five 'decads' or parts.  used the conventional date of 1780? with a question mark for decads 3, 4, and 5 based on Lisney (1960). Evenhuis (1997: page 343) established that the decad 3, where Musca personatus is described on page 79, was dated as 1779 based on the latest date of the plates. Thus, the year of publication should be 1779.
Distribution. Europe, European parts of Russia and Transcaucasia, but needs reassessment.
Distribution. Holarctic, but not in northern Africa.

Rhingia campestris Meigen, 1822
Reference. ; ; ; . Genetics. One specimen was successfully sequenced (MN622049), and its BIN is BOLD:ABZ3049. Our sequence is exactly the same as other sequences of R. campestris previously published.
Distribution. Europe, Transcaucasia, and European parts of Russia into Siberia.

Sericomyia volucellina Portschinsky, 1881
Reference.  as Conosyrphus volucellinus (Portschinsky, 1881);   Reference. ; ; . Genetics. We sequenced one specimen (MN622056), and its COI barcode is identical as other sequenced specimens listed in BOLD and very similar (> 98.62% similarity) to other non-public and published sequences of this species. The BIN for this taxon is BOLD:AAZ5247.
Distribution. Mountains of Central Europe, Balkans, Carpathians, Turkey and the Caucasus Region.
Distribution. Northern and Central Europe, Turkey, Transcaucasia, through Russia to Sakhalin.
Distribution. Europe, European parts of Russia, and Caucasus Region.

Spilomyia triangulata Van Steenis, 2000
Reference. Stackelberg (1958) as Spilomyia digitata (Rondani, 1865);  as Spilomyia digitata. Distribution. Alps, North Macedonia, Greece, Turkey, and Transcaucasia. Remarks. Van Steenis (2000) described this taxon from the eastern part of the Mediterranean Basin (with a record from France), and among the paratypes he listed material collected in Gelendzhik (Northern Caucasus); likely the same specimens that Stackelberg (1958) reported as S. digitata from Gelendzhik and, later on,  listed from Transcaucasia.

Syritta pipiens (Linnaeus, 1758)
Remarks.  and  listed this species from Transcaucasia, and Speight (2018a) included the Caucasus in its distributional range, but it has never been previously reported from Georgia to our knowledge. Reported for Georgia for the first time.
Distribution. Palaearctic, Western North America, and Taiwan. Remarks. The specimen ZFMK-TIS-8002691 fits the description of Syrphus rectus subsp. bretoletensis Goeldlin de Tiefenau, 1996 with possession of almost entirely yellow legs and wings with extensive areas bare of microtrichia. The taxonomic status of this subspecies is still in discussion, whether it is a valid subspecies of the North American Syrphus rectus Osten Sacken, 1875 or another species . Ssymank et al. (1999) tentatively synonymised S. rectus bretolensis with S. vitripennis, but without explanation. The obtained DNA barcode for ZFMK-TIS-8002691 is identical to the other COI sequences of S. vitripennis, and we consider this specimen as S. vitripennis.

Remarks.
The year of publication for this species is a convention.  used the conventional dates based on Lisney (1960): 1776 for decad 1, 1776? for decad 2, and 1780? for decads 3, 4, and 5. Evenhuis (1997: page 342) found that the decad 2, where Musca scitus is described on page 41, was dated as 1778 in the "Discours préliminaires" to the Encyclopédie méthodique par ordre des matières -Insectes. Thus, the year of publication should be 1778.

Volucella inanis (Linnaeus 1758)
Reference. ; ; . Genetics. We sequenced two specimens (MN622109, MN622110) and their COI barcode were identical. The Barcode Index Number Registry lists a BIN for this taxon (BOLD:AAZ4733) with an average p-distance variation of 0.04% within the BIN members (0.31% max).

Xanthogramma maculipenne Mik, 1887
Reference. . Distribution. Former Yugoslavia, Iran and Transcaucasia. Remarks.  did not list this taxon as a European species as it has not been mentioned in any recent literature from the former Yugoslavia. Mik (1887) described this species from an undefined number of males and females collected in Göygöl (= Helenendorf = Khanlar), Azerbaijan. He stated that his new species was similar to X. pedissequum (as ornatum Meigen) but also mentioned their differences: four yellow maculae on the pleuron (like in X. dives and X. stackelbergi; see Van Steenis et al. 2014), almost entirely dark metatibia, wing with two dark maculae (one at the apical part of the cell r 2+3 and another one reaching cells r 1 and r 4+5 ), and the coloration of the membrane between abdominal tergites and sternites (yellow between the tergite 2 and sternite 2, and also yellow on basal half between tergite 3 and sternite 3). Violovitsh (1975) keyed out X. maculipenne near Xanthogramma evanescens Becker in Becker & Stein, 1913, a taxon described from Morocco, based on a dark apical macula on the wing; but X. dives was not included in Violovitsh (1975) as it was considered a junior synonym of X. pedissequum at that time. Based on the original description, this taxon is very similar to X. dives. The study of the type material is needed to resolve and confirm the identity of this taxon.
Distribution. Europe, but it needs reassessment due to confusion with X. stackelbergi and X. dives.
The year of publication for this species was a convention.  used the conventional dates as established by Lisney (1960): 1776 for decad 1, 1776? for decad 2, and 1780? for decads 3, 4, and 5. Evenhuis (1997: page 342) found that the decad 2, where Musca pedissequus is described on page 61, was dated as 1778 in the "Discours préliminaires" to the Encyclopédie méthodique par ordre des matières -Insectes. Thus, the year of publication should be 1778. Genetics. We sequenced the single collected female (MN622123). See comments on Genetics and Remarks under X. dives.
Distribution. Needs reassessment, but known from Europe, Crimea, and European parts of Russia.
Remarks. Reported for Georgia for the first time.

Xylota (Xylota) sylvarum (Linnaeus, 1758)
ern Caucasus is part of the typically called European parts of Russia and is far from the Caucasus Mountain range (Greater Caucasus). Thus, we decided to not include this species in the present checklist, but we acknowledge the possibility that this species can occur in Georgia.

Discussion
The flower fly fauna of Georgia is quite similar to the fauna found in Central Europe, with some species endemic of Transcaucasia and a few more species occurring also in Turkey and Iran (see Kustov 2006). The DNA COI sequences obtained for the present work are the first DNA barcodes of Syrphidae ever published from Georgia and enlarge the knowledge on the molecular variability for the studied species. Five very common Palaearctic species were collected abundantly, i.e., Melanostoma mellinum (218 specimens), Syrphus ribesii (109), Sphaerophoria scripta (94), Eristalis tenax (88), and Melanostoma scalare (86). Two species recorded for the first time from Georgia were collected in relatively large numbers, i.e., Neoascia subannexa (36) and Syrphocheilosia claviventris (25). These taxa are not ubiquitous but can be found in relatively large numbers locally on sites they occur. This prompts us to continue our survey of the Syrphidae fauna in Georgia and in the Caucasus Region in the coming years, as we expect more species to be recorded from this country.