A contribution towards checklist of fungus gnats (Diptera, Diadocidiidae, Ditomyiidae, Bolitophilidae, Keroplatidae, Mycetophilidae) in Georgia, Transcaucasia

Abstract The fungus gnats of Georgia are studied based on 2682 specimens collected from 57 localities during 2011–2019. Altogether, 245 species are recorded including four species of Bolitophilidae, three species of Diadocidiidae, two species of Ditomyiidae, 34 species of Keroplatidae and 202 species of Mycetophilidae. 230 and 188 species are recorded from Georgia and the whole of Transcaucasia for the first time, respectively. Three new species – Sciophila georgei sp. nov., Leia katae sp. nov. and Anatella metae sp. nov. – are described including detailed illustrations of the male terminalia. Photographs are provided for an additional 38 species to highlight a variability of their general facies. Combined with earlier published data, the number of fungus gnat species in Georgia is set at 246. The estimated diversity of fungus gnats in Georgia is calculated using non-parametric methods and discussed with respect to other Western Palaearctic regions.


Introduction
The last decades can be characterized by an upturn of systematics, taxonomy and biodiversity studies (e.g. Padial et al. 2010;Kõljalg et al. 2020;Wheeler 2020). That is also true in the case of the insects order Diptera (e.g. Wiegmann et al. 2011;Kirk-Spriggs and Sinclair 2017;Borkent et al. 2018) including the superfamily Sciaroidea (e.g. Kjaerandsen et al. 2007;Borkent and Wheeler 2012;Ševčík et al. 2013;Fitzgerald and Kerr 2014). Seven families and a insertae sedis group are included in Sciaroidea (Ševčík et al. 2016;Mantič et al. 2020), whereas five of them, viz. Diadocidiidae, Ditomyiidae, Bolitophilidae, Keroplatidae and Mycetophilidae are conjoined under a common name 'fungus gnats'. Today, more than 5,500 species of fungus gnats are known globally (Evenhuis and Pape 2021; Fungus Gnats Online Authors 2021), however, their actual diversity is insufficiently known, especially in tropical regions of the world. As expected, the group is best studied in Europe with about 1,200 named species (Chandler 2013) yielded by more than 200 years of studies pioneered by the "father" of dipterology J.W. Meigen (e.g. Meigen 1804, 1818. Nevertheless, even in Europe, new species are described annually and e.g. in Nordic countries nearly 120 new species are waiting to be described (Kjaerandsen and Søli 2020). While fungus gnats are mostly forest dwellers preferring shady and humid habitats, some species are also recorded from more open landscapes (Falk and Chandler 2005). They are small to medium size nematocerous flies with a humpbacked habitus, prominent coxae and hyaline or patterned wings (see e.g. Figs 8,9). The trophic strategy of fungus gnats is diverse: the majority of the known associations are those with fungal fruiting bodies or myceliumpenetrated forest litter including decaying wood but several species develop in other terrestrial habitats and/or can also be sporophagous or predators in the larval stage (e.g. Matile 1997;Ševčík 2010;Jakovlev 2012;Põldmaa et al. 2016;Mantič et al. 2020).
Transcaucasia, the area southwards from the Greater Caucasus Mountains that includes the countries of Georgia, Azerbaijan and Armenia, is considered one of the biodiversity hotspots of the world, with a remarkable number of endemic species (Myers et al. 2000). However, limited attention has been paid to the biodiversity research in the area so far (Mumladze et al. 2020) and most organism groups, including Diptera and fungus gnats in particular, are rather superficially studied. There are 33 species of fungus gnats recorded from Azerbaijan (Zaitzev 1994Zaitzev and Ševčík 2003) and seven species from Armenia Plassmann 1985, Zaitzev 1994). From Georgia, only one species was known (Zaitzev 1994) prior to Kurina and Jürgenstein (2013) who described two new Orfelia Costa (Keroplatidae) species from Marelisi, NW of Borjomi. Later on, Jürgenstein et al. (2015), Kurina et al. (2015), Kurina (2018), Thormann et al. (2019) and Ševčík et al. (2020) provided data on another twelve species and the number of fungus gnat species from Georgia is currently set at 15. Furthermore, an additional 24 fungus gnat species have been listed to occur in Transcaucasia but without a specified region (Zaitzev 1994. Concerning neighbouring areas, 91 species of fungus gnats are recorded from the northern slopes of the Great Caucasus ridge, most of them from the surroundings of Mt Elbrus (Joost and Plassmann 1976, 1979, 1992, Plassmann 1976.
During the last decade, a considerable amount of fungus gnat material from Georgia has accumulated in the author's possession. The aim of the current contribution is to provide results of the study based on that material along with summarising all available published information on Georgian fungus gnats.

Material and methods
The material was collected from 2011 to 2019 using different methods in the course of 61 collecting events from 57 localities in Georgia (Table 1, Fig. 1). The majority of the material was collected sweeping during three expeditions by the author in May of 2012 and 2013 and August-September 2014. Additional material from Malaise trap samples is included from the provinces Samegrelo-Zemo-Svanethi, Imereti and Kaheti; a sporadic material as a by-product of light trap collecting is also included ( Table 1). The collecting localities (see Fig. 2 for examples) varied from more open landscape in Vardzia (Table 1: SJ-10) to highly forested mountain areas in Kintrishi (Table 1: A-5-8), Mtirala (Table 1: A-1-4) and Borjomi-Kharagauli (Table 1: I-5-17) National Parks, and subalpine areas in the surroundings of Stepantsminda (Table 1: MM-1-6), Bakuriani (Table 1: SJ-6-7) and Ushguli (Table 1: SZS-2-3).
The vast majority of the material was initially preserved in 70% ethyl alcohol where most of it is also stored after determination. Every species per locality is arranged in a separate glass vial equipped with collecting and determination labels. Some specimens  Table 1. Table 1. Collecting data of fungus gnats in Georgia arranged by administrative regions of the country. Codes for the collecting events are used on the Figure 1 and within the list of species. The asterisk (*) indicates collecting with a Malaise trap for which the exact collecting dates are provided in the text. were double pinned directly after collecting, whereas part of the initially alcohol-preserved specimens were mounted using the method described by Vockeroth (1966) and double pinned thereafter. The majority of the material was determined directly in alcohol as that also allowed observation of the terminalia. However, in a number of cases a more detailed study of male terminalia proved to be unavoidable. For that, terminalia were detached and treated with about 10% warm potassium hydroxide followed by neutralization with acetic acid and washing with distilled water. Terminalia were studied in glycerine and stored as glycerine preparations in small plastic vials attached to the rest of the specimen (see also Kurina 2008a). Illustrations of the terminalia were prepared using a U-DA drawing tube attached to a compound microscope Olympus CX31. The digital images of the general habitus and terminalia were combined using the software LAS V.4.1.0. from multiple gradually focused images taken by a Leica DFC 450 camera attached to a Leica 205C stereomicroscope (see also Jürgenstein et al. 2015). Adobe Photoshop CS5 was used for editing the figures and compiling the plates. The morphological terminology follows Søli (1997Søli ( , 2017 and that of the male terminalia is explained in Figs 4-7. The estimated species richness according to different non-parametric methods (Fig. 14) is calculated using the software EstimateS, Version 9.1.0. (Colwell 2013).
The material is deposited in the following collections: The majority of the studied specimens are deposited in IZBE which is not repeated in the species list for every specimen. However, the material collected by X. Mengual (Bonn, Germany) in 2019 is divided between three institutions and the depository is specified in listed material sections below.

Results
Altogether, 2682 studied specimens were identified to 245 different species, viz. four species of Bolitophilidae, three species of Diadocidiidae, two species of Ditomyiidae, 34 species of Keroplatidae and 202 species of Mycetophilidae including three species described as new to science. One additional species of Keroplatidae was included from the literature data (Zaitzev 1994). Moreover, six additional putatively new Mycetophilidae species were recorded, all represented by singletons, some of them of poor quality. Description of these species is deferred pending additional material to be collected. These six species are not included in the species list but are considered in the species richness calculations and distribution analysis (see Discussion). 230 and 188 species are recorded from Georgia and the whole Transcaucasia for the first time, respectively. In the species list, all available literature sources are cited for the species recorded earlier in Georgia and/or in Transcaucasia generally. The studied material is listed, using abbreviations of collecting events provided in Table 1, followed by total number of studied specimens. Distribution in Georgia is given by administrative provinces and the general distribution by zoogeographical regions or subregions. The latter is provided according to Chandler (2013) and subsequent published information available. Some remarks on distribution and/or taxonomy are included for species of special interest. To illustrate the diverse habitus of recorded fungus gnat species a gallery of photographs is provided (Figs 8,9,11,12). In the list of species, the classification follows Fungus Gnats Online (http:// www.sciaroidea.info/) except in two cases. Firsty, the subfamily Platyurinae of Keroplatidae is used according to Mantič et al. (2020). Secondy, Brachycampta Winnertz, 1863 is reinstated to the generic status from a subgenus of Allodia Winnertz, 1863 in accordance with a thorough study by Magnussen (2020); this opinion is also implemented in the recent checklist of fungus gnats of Norway by Kjaerandsen and Søli (2020). Diagnosis. Sciophila georgei sp. nov. can be distinguished by combination of the characters of the male terminalia as follows: lateral branch of gonostylus ventrally with two apical spine-like setae, small internal branch of gonostylus with one spine-like seta, tergite 9 large with medially rising apical margin that bears two large and simple setae, parameres straight and long, extending over tergite 9 apically, aedeagus small, star-shaped.

The new species
Description. Male. Body length 2.7-2.8 mm (n = 2). Coloration. Head with vertex and frons dark brown, face and clypeus brown and mouthparts including palpus pale yellow. Scape and pedicel yellow. First three or four flagellomeres yellowish, rest of flagellomeres light brown. Scutum entirely dark brown, antepronotum and proepisternum yellowish, anepisternum, anepimeron and katepisternum light brown, laterotergite and mediotergite brown, scutellum brown. Thoracic setae all yellowish. Wing hyaline, all veins brown including radial veins somewhat darker. Halter with stem and knob pale yellow. All coxae, femora and tibiae yellow, tarsi yellow but seem darker because of dense brown setae. Tibial setae brown, spurs yellowish. Abdomen with tergites light brown, 1-3 tergites somewhat lighter, all sternites yellowish. Abdominal vestiture yellow. Terminalia brown. Head. Ocelli in a shallow triangular arrangement. Medial ocellus somewhat smaller than laterals. Frontal furrow complete. Clypeus subrounded, about as long as broad. Fourth flagellar segment about as long as wide, apical flagellar segment 2.25 times as long as wide basally. Flagellar segments with dense yellowish short setae. Thorax. Scutum covered with short setae, with marginal and prescutellar setae stronger. Antepronotum with 8-9 setae. Proepisternum with 6-7 setae. Anepisternum with 5-6 setae on upper part, katepisternum and anepimeron non-setose. Laterotergite with 7-9 setae on posterior half. Mediotergite with 10-15 setae on lower part. Metepisternum with setulae. Scutellum with setulae and marginal setae not arranged in pairs. Wing. Length 2.5-2.8 mm, length to width 2.4-2.7. Wing membrane uniformly covered with micro-and macrothichia. All veins setose, except sc-r, Rs, R 2+3 . Costa reaches about one fifth from R 4+5 to M 1 . Sc ending on C before level of furcation of posterior fork. Sc-r located slightly before Rs. r-m about two times as long as m-stem. M 4 basally very faint or shortly interrupted at base. Legs. Ratio of femur to tibia for fore, mid and hind legs: 0.83-0.93; 0.89-0.97; 0.84-0.92. Ratio of tibia to basitarsus for fore, mid and hind legs: 1.26; 1.42-1.65; 1.33-1.37. Fore tibia with a spur 2.29-2.81 times of tibial maximum width. Mid tibia with anterior spur 3.08-3.15 times and posterior spur 3.42-3.69 times of tibial maximum width. Hind tibia with anterior spur 2.50-2.60 times and posterior spur 3.47-3.57 times of tibial maximum width. Terminalia (Fig. 4A-G). Gonocoxites fused for short distance ventrobasally forming medial triangular lobe with medial more sclerotized longitudinal ridge internally. Ventromedial margin of gonocoxite with a membranous flange drawn medially out into digitate apically hooked lobe. Gonocoxite covered with uniform setae except non-setose lateroapical and dorsomedial marginal areas. Dorsoposterior margin of gonocoxite with two prominent medially directed setae. Gonocoxal apodeme anteriorly enlarged, shoe-shaped, well discernible in dorsal view. Tergite 9 large, slightly convergent posteriorly, extending over gonocoxites, subapically constricted with two prominent simple setae apically, apical margin medially rising. Parameres long and straight, apically slightly widening, extending over tergite 9 apically. Aedeagus small, star-shaped, medially with posteriorly projecting digitate process. Lateral branch of the gonostylus laterally setose with aggregation of spine like setae along posterior margin; ventral part extended with two prominent apical spinelike setae. Medial branch of gonostylus with 25-30 furcated megasetae. Small internal branch of gonostylus with one prominent medially directed seta.
Female. Unknown. Etymology. The species is named in honour of Prof. George Japoshvili (Tbilisi, Georgia) in recognition of his contribution to study of the insects' diversity in Georgia and his invaluable help in collecting the fungus gnat material that underlies the current communication. He was also the collector of the type material of this species.
Remarks. More than 190 species of Sciophila Meigen are known wordwide (Kurina 2020a, Taber 2021); the most comprehensive key to the Holarctic species is still that by Zaitzev (1982). Fortunately, all subsequently described species are supplemented with appropriate illustrations of the male terminalia (e.g. Polevoi 2001;Salmela and Kolcsár 2017;Taber 2021) that provides an adequate compendium of the morphological distinctions. Following the key by Zaitzev (1982), the new species runs to couplet 31 because of (1) wing with both macro-and microtrichia, (2) gonostylus without additional branches, (3) lateral branch of the gonostylus with two large setae ventroapically, (4) small internal branch of the gonostylus with one large seta, and (5) gonocoxites dorsoapically without protruding appendages. However, S. georgei sp. nov. differs from the species included in this couplet by details in the male terminalia. Notably, by the characters of tergite 9 (large, posteriorly convergent, extends over gonocoxites, bears two prominent simple setae apically, apical margin medially rising) and parameres (long, straight, extending over tergite 9 apically).  Diagnosis. Leia katae sp. nov. can be distinguished by the combination of characters as follows: thorax bicolored (scutum yellow, with brown longitudinal stripes; katepisternum with lower half brown), wing tinged yellowish, with faint preapical brownish band, male terminalia with bipartite gonostylus (lateral prong shorter, convolute and apically hooked; medial prong longer, tapering with preapical small tooth at ventral margin).
Description. Male. Body length 6.7-6.9 mm (n = 2). Coloration. Head with vertex brown, frons yellow, face, clypeus and mouthparts including palpus pale yellow. Scape and pedicel pale yellow. First two flagellomeres yellowish, flagellomeres 3-14 brown. Thorax bicoloured: scutum yellow with three brown longitudinal stripes, which are posteriorly completely fused, lateral stripes begin at a distance of one third from anterior margin, medial stripe shortly split anteriorly, lateral parts of scutum yellow; antepronotum, proepisternum and anepisternum yellow, posterior margin of anepimeron light brown, katepisternum with lower half brown and upper half yellow, laterotergite brown with posterior half yellowish, mediotergite brown, scutellum basally yellowish, apically brown. Thoracic setae all yellow. Wing with yellowish tinge and preapical very faint transverse brownish band reaching to M 2 , all veins yellowish including radial veins somewhat darker. Halter with stem and knob pale yellow. All coxae and femora yellow, except hind femur apically with narrow brown band, all tibiae, tarsi yellow but seem darker because of dense brown setae. Tibial setae brown, spurs yellowish. Abdomen with all tergites brown and sternites yellow. Abdominal vestiture yellow. Terminalia brown with gonocoxite medially and gonostylus anteriorly yellow. Head. Ocelli in a linear arrangement. Medial ocellus about twice smaller than laterals, which are separated from eye margins by less than their own diameter. Frontal furrow complete. Clypeus obovoid. Fourth flagellar segment about as long as wide, apical flagellar segment 2.5 times as long as wide basally. Flagellar segments with dense yellowish short setae. Thorax. Scutum densely covered with setae, with marginal and prescutellar setae stronger. Antepronotum with 6-7 strong and a number of weaker setae. Proepisternum with one very strong seta at anterior margin about 10 weaker setae. Anepisternum, katepisternum and anepimeron non-setose. Laterotergite with long fine setae on posterior half. Mediotergite non-setose. Scutellum with a row of marginal setae including two pairs remarkably stronger. Wing. Length 5.3-5.7 mm, length to width 2.3-2.8. All veins setose, except Sc, sc-r, Rs and extreme base of M 1 . Sc ending on C at level of furcation of posterior fork. R 4+5 3.3 times as long as R 1 . r-m 1.47 times as long as m-stem. M 1 and M 2 apically convergent, apical third of both veins faint. M 4 Figure 5. Leia katae sp. nov., male terminalia A dorsal view B lateral view C ventral view D gonocoxite and gonostylus, ventral view. Abbreviations: aed = aedeagus, cer = cercus, ej ap = ejaculatory apodeme, gc = gonocoxite, gc vmp = ventromedial process of gonocoxite, gc vpp = ventroposterior process of gonocoxite, gst lp = lateral prong of gonostylus, gst mp = medial prong of gonostylus, hyp = hypoproct, par = paramere, tg 9 = tergite IX. Scale bars: 0.2 mm. interrupted at base. Rs located distally of the anterior fork. Legs. Ratio of femur to tibia for fore, mid and hind legs: 1.16; 0.95; 0.86. Ratio of tibia to basitarsus for fore, mid and hind legs: 1.00; 1.66; 2.00. Fore tibia with a spur 2.95 times of tibial maximum width. Mid tibia with anterior spur 3.33 times and posterior spur 3.96 times of tibial maximum width. Hind tibia with anterior spur 3.33 times and posterior spur 4.58 times of tibial maximum width. Terminalia (Figs 5A-D, 6A-C). Gonocoxite with setae on apical fifth only. Ventromedial process of gonocoxite elongated ovoid with a row of long setae apically and an aggregation of shorter setae on apical fourth. Ventroposterior margin of gonocoxite drawn into a wide membraneous non-setose medial lobe and a digitate more protruding lobe with one prominent and 2-3 weaker apical setae. Tergite 9 membraneous, somewhat tapering, apically evenly rounded with apicocentral patch of short setae. Gonostylus bipartite: lateral prong shorter, convolute and apically hooked; medial prong longer, tapering with preapical small tooth at ventral margin. Aedeagus with sclerotized, cup-shaped apical portion, ejaculatory apodeme bilobed. Paramere about 1.6 times as long as aedeagus, bowed in lateral view, apically tapering, with ventral flange drawn out into a triangular membranous process in the middle; anteriorly, parameres fused into a complex membranous structure with anterior concavity and well protruding lateral corners. Hypoproct with protruding apicolateral corners and medial part that bears a group of stout setae.
Female. Unknown. Etymology. The species is named after my daughter Katariina (born 3 November 2000), an enthusiastic student of biology at the University of Tartu (Estonia). She participated in a trip to Georgia in 2017 that yielded several specimens of this study and she always insists we call her Kata.
Remarks. There are 166 Leia Meigen species known worldwide including 33 in the Palaearctic region (Polevoi and Salmela 2016). Leia katae sp. nov. differs from all known Palaearctic and Nearctic species by its peculiar structure of the gonostylus that is bipartite: medial prong long and slender with a preapical tooth, and lateral prong apically hooked, about 2/3 of the medial prong. Diagnosis. Anatella metae sp. nov. is characterized by the presence of a strong posteroventral fringe on mid femora with a row of strong setae, absence of anterior spur on mid tibia, absence of setae on hind coxa basally. The new species is closest to A. atlanticiliata Chandler and Ribeiro but differs in characters of the male terminalia: ventral branch of the gonostylus about twice as long as the dorsal branch, dorsal branch of the gonostylus with long and slender medial prong, medial branch of the gonostylus slender and apically hooked.
Description. Male. Body length 2.7-2.9 mm (n = 2). Coloration. Head with vertex, frons, face and clypeus brown, mouthparts including palpus pale yellow. Scape, pedicel and base of first flagellomere yellow, rest of flagellum light brown. Thorax with scutum and lateral parts light brown. Thoracic setae yellowish to brown, with thicker setae darker than finer ones. Wing hyaline, unmarked with yellowish tinge. Halter with stem and knob pale yellow. Legs yellow, tarsi yellow but seem darker because of dense brown setae. All setae on legs brown, tibial spurs yellowish. Abdomen mainly brown with first two segments somewhat lighter. Abdominal vestiture brown. Terminalia light brown. Head. Ocelli two, very close to eye margins, with dark brown patches at anterior margin. Frontal furrow complete. Clypeus rectangular. Fourth flagellar segment about 2.5 times as long as wide, apical flagellar segment 2.5 times as long as wide basally. Flagellar segments with dense whitish setae about one third of segments' width. Thorax. Scutum covered with setae, with marginal and prescutellar setae stronger. Antepronotum with 2 strong and 10-15 weaker setae. Proepisternum with two strong and 2-3 weaker setae.
Anepisternum, katepisternum and anepimeron non-setose. Laterotergite with about 10 setae on upper half. Mediotergite non-setose. Scutellum with about 10 setae on upper surface. Wing. Length 2.39-2.70 mm, length to width 2.75-2.90. C, R, R 1 , R 4+5 setose, all other veins non-setose. C produced halfway between R 4+5 and M 1 . r-m about as long as m-stem. Posterior fork at the level of anterior fork or slightly before. CuA slightly sinuous. Legs. Ratio of femur to tibia for fore, mid and hind legs: 1.08-1.17; 0.97-1.00; 0.65-0.90. Ratio of tibia to basitarsus for fore, mid and hind legs: 0.96-1.00; 1.21-1.28; 1.41-1.77. Fore tibia with a spur 2.00 times of tibial maximum width. Mid tibia with anterior spur absent and posterior spur 2.27-2.40 times of tibial maximum width. Hind tibia with anterior spur 2.71-3.33 times and posterior spur 3.93-4.66 times of tibial maximum width. Strong posteroventral fringe of mid femora with row of strong setae. Hind coxa without basal setae. Terminalia (Fig. 7A-G). Gonocoxite ventrally with (1) V-shaped wide incision anteriorly, (2) posteromedial non-setose tapering projection with deep slit, and (3) posterolateral large apically setose lobes. Gonostylus divided into four branches ( Fig. 7F-G). The ventral branch of the gonostylus elongated digitate, apical half setose and with one strong seta apically deviating from other setosity. Dorsal branch of the gonostylus about half length of the ventral branch, divided into two prongs: medial finger like bare prong and lateral large apically and basally setose prong. Medial branch of the gonostylus slightly shorter than dorsal branch, slender, apically hooked. Internal branch of the gonostylus membranous, convolute with anterior lamellae.
Etymology. The species is named after my daughter Liisa-Meta (born 9 October 2004), a keen naturalist who also participated in a trip to Georgia in 2017.
Remarks. There are about 50 Anatella Winnertz species known in the Holarctic region (cf. Fungus Gnats Online Authors 2021), the vast majority of which are adequately described and figured. In having posteroventral fringe of mid femora with strong setae and absence of anterior spur of mid tibia, A. metae sp. nov. resembles A. atlanticiliata Chandler & Ribeiro, 1995 known only from Madeira Island. Also, the male terminalia of both species share the general outline (cf. Chandler and Ribeiro 1995: fig. 27). However, A. metae differs in the structure of the gonostylus as follows: (1) ventral branch of the gonostylus twice as long as dorsal branch (only somewhat longer in A. atlanticiliata), (2) dorsal branch of the gonostylus with medial prong long, anchored to lateral prong basally (medial prong short, anchored to lateral prong subapically in A. atlanticiliata), and (3) medial branch of gonostylus slender, apically hooked (medial branch stout, slightly curved in A. atlanticiliata).  General distribution. Palaearctic. Remarks. In Transcaucasia recorded from Azerbaijan (Zaitzev 1994  Remarks. In Transcaucasia recorded from Azerbaijan (Zaitzev 1994).

Pyratula perpusilla (Edwards, 1913)
Material. 16♂♂, SJ-4. Total: 16♂♂. Distribution in Georgia. Samtskhe-Javakheti. General distribution. Europe. Remarks. The P. perpusilla species-group includes at least seven closely related species in Europe, separable only by small details of male terminalia (Chandler and Blasco-Zumeta 2001). The studied Georgian specimens have the ventroapical margin of the gonocoxite with setose lobe (= without asetose protuberance) that is shared by three species, viz. P. perpusilla, P. alpicola Chandler, 2001 andP. oracula Chandler, 1994. The aedeagal complex is considerably short (elongate in P. oracula) and the aedeagal sheath is interrupted medially on the ventral side (with complete bridge in P. alpicola). However, the Georgian specimens are slightly different from P. perpusilla as figured by Chandler and Blasco-Zumeta (2001: Figs 9-12) in having the distal dorsal corner of the aedeagal seath with a blunt protuberance that is otherwise typical to P. alpicola. The material was compared to that of P. alpicola and P. oracula from North Italy (cf. Kurina 2008b) and, pending a further molecular study of this species-group, is considered to be conspecific with P. perpusilla.    General distribution. Caucasia. Remarks. Recorded earlier from North Caucasus and Azerbaijan (Zaitzev 1994). Remarks. In Transcaucasia recorded from Azerbaijan (Zaitzev 1994). Zaitzev, 1994 Georgian source. Kurina et al. 2015: 116 (figs 11, 12, 16). Remarks. Known only from type locality in Azerbaijan (Zaitzev 1994).

Sciophila georgei sp. nov.
Material. See in species description above. Distribution in Georgia. Kakheti. General distribution. Georgia.

Boletina dubia (Meigen, 1804)
Material. 5♂♂, A-1; 3♂♂, A-3. Total: 8♂♂. Distribution in Georgia. Adjara. General distribution. Europe. Remarks. The Georgian specimens have the ventral lobe of the gonostylus with a blunt small spine apically that is absent in studied specimens from Estonia and Sweden as well as in published figures (e.g. Landrock 1927, Hutson et al. 1980, Zaitzev 1994. Otherwise, the male terminalia including aedeagal complex do not have any substantial differences. Therefore, the Georgian material is considered to be conspecific pending further, more thorough study including that based on DNA sequencing.  Remarks. Known only from Grete and Cyprus (Caspers 1991, Chandler et al. 2006, Ribeiro and Chandler 2007.

Palaeodocosia vittata (Coquillett, 1901)
Material. 1♂, A-1; 1♂, I-6. Total: 2♂♂. Distribution in Georgia. Adjara, Imereti. General distribution. Holarctic. Remarks. This very rare species was until recently recorded only from Channel Islands and Central Europe but Kurina (2020b) found it also from Japan. The record from Georgia suggests a wider distribution in the Palearctic region.

Remarks.
A widely distributed Palaearctic species that has expanded its range in Europe during recent decades and is locally common also in anthropogenic environments (Kurina et al. 2011, pers. observations).

Leia katae sp. nov.
Material. See in species description above.
Remarks. Listed to occur in Transcaucasia without further details .  sweeping studies will probably increase that number considerably (see also below). As expected, the majority of the recorded species are widely distributed in the Palaearctic or Holarctic regions (38% and 26% of the recorded species, respectively), while 22% of species are restricted to Europe and 7% to the Western Palaearctic (Fig. 13). In addition, one species was so far known only from the Eastern Palaearctic and 17 species (11 described and 6 undescribed) are classified (tentatively) as Caucasian endemics. These proportions can change as fungus gnats are rather poorly known in several Palaearctic regions including the East Palaearctic, Asia Minor, Central Asia, as well as other regions in Caucasia.

Phronia tenuis
The estimated species richness is the highest when calculated using Jackknife-2 nonparametric estimator (404 species, Fig. 14). This method has been discussed as possibly overestimating the true richness (e.g. Poulin 1998). On the other hand, Smith and van Belle (1984) showed that both Jackknife and Bootstrap estimators underestimate the actual number of species if there is a large number of rare species considered and number of samples is low. That can also be the case in the current data as the number of recorded singletons and doubletons is exceptionally high (82 and 42 species, respectively) and the number of species recorded from one sample only (= unique species) constitutes 43% of the observed diversity (107 out of the 251). Within the listed species, only nine were recorded from more than ten samples and 31 species from 5-10 samples. To compare, relatively well studied countries of similar size in Central and Northern Europe (e.g. Czech Republic, Slovak Republic, Estonia) have roughly 600 fungus gnat species recorded (Ševčík andKošel 2009, Ševčík andKurina 2011a, b, pers. observation). Taking into account the mountainous landscape, high diversity of Figure 13. Grouping of the recorded Georgian fungus gnat species in accordance with their known distribution.
habitats, microclimates in Georgia and that several regions were not covered by sampling of the current study (see Fig. 1), it can be presumed that the observed 245 species (+ one based on the literature data) do not constitute more than half of the actual diversity, probably less.
Surprisingly, the most abundant species was Synapha fasciata (769 specimens from 19 samples) followed by Orfelia georgica (175 specimens from 14 samples). In the European boreal and temperate regions, the most abundant species belong frequently to the subfamily Mycetophilinae and/or to the genera Boletina Staeger and Mycomya Rondani. Several of the recorded species considerably increase the knowledge of their distribution, the most remarkable of them include: Neoempheria brevilineata (earlier from Japan only), Clastobasis loici (earlier from Europe and Japan), Lusitanoneura chandleri (earlier from the Mediterranean Islands), Zygomyia setosa (earlier with scattered distribution in Europe), Manota unifurcata (earlier from Europe only).
From the material underlining this study, four new species have been described earlier (Kurina and Jürgenstein 2013;Kurina 2018;Ševčík et al. 2020), three new species are described above and six putatively new species are left to be described in the future due to insufficiency of the available material or its quality. More exhaustive sampling will naturally yield a number of new taxa to be described in the future.