Checklist of the fungus gnats of Finland: Bolitophilidae, Diadocidiidae, Ditomyiidae, Keroplatidae and Mycetophilidae (Diptera)

Abstract A checklist of the ’fungus gnat’ group of families in Sciaroidea: Bolitophilidae, Diadocidiidae, Ditomyiidae, Keroplatidae and Mycetophilidae (Diptera) recorded from Finland. At present, the known Finnish fauna comprises 767 recognized species in 78 genera; 21 species of the family Bolitophilidae, 5 of the family Diadocidiidae, 2 of the family Ditomyiidae, 47 of the family Keroplatidae and 692 of the family Mycetophilidae. The unassigned genus Sciarosoma Chandler, 2002 is not included in this paper because it is listed with Sciaridae. The most relevant synonyms, on which species were ever listed from Finland in Hackman (1980) and subsequent authors are indicated in the checklist. Eighteen species names of wrong records were removed.


Introduction
Fungus gnats are a rich assemblage of nematocerous flies (Diptera, Nematocera) placed in the infraorder Bibionomorpha and superfamily Sciaroidea, currently divided into eight families (Blagoderov and Grimaldi 2004). Five of these families (Bolitophilidae, Diadocidiidae, Ditomyiidae, Keroplatidae and Mycetophilidae) are called informally 'fungus gnats' by most European authors. Species in these families are morphologically closely related and the group is also ecologically uniform.
Adults of fungus gnats are generally quite easily recognized by their habitus. They are slender to moderately robust flies between 2 and 10 mm (a few up to 15 mm) in body length, with long antenna, a high and often strongly arched thorax made distinctly higher by the long, stout and tight-sitting coxae of their legs. Their wings have reduced and variable venation that is quite distinctive for the different families and much used also to classify genera. Their body and legs are often covered with strong bristles. As larvae the majority of fungus gnat species are mycetophagous, associated with fungi, either fruiting bodies or mycelia in dead wood and soil litter.
Here I cover all the Finnish fungus gnat fauna of the families Bolitophilidae, Diadocidiidae, Ditomyiidae, Keroplatidae, and Mycetophilidae. In Europe, the superfamily Sciaroidea further includes two large families, the Sciaridae -black-winged fungus gnats and the Cecidomyiidae -gall midges (Søli et al. 2000) although some authors, e.g. Hippa and Vilkamaa (2006) consider the Cecidomyiidae as the sister group of all other Sciaroidea. They differ markedly in habitus and larval biology and are presented elsewhere. Finally, the unassigned genus Sciarosoma Chandler, 2002 is not included in this checklist since it is listed with the family Sciaridae according Hippa and Vilkamaa (2006), but see also opinion by Jaschhof et al. (2006).
Systematics and nomenclature of the enumeration follow the online checklist of Nordic fungus gnats (Kjaerandsen 2012). Only the most relevant synonyms, on which species were ever listed from Finland, are included in the checklist.
Adults of the North European species can largely be identified using Hutson et al. (1980) and Zaitzev (1994) − Bolitophilidae, Diadocidiidae, Ditomyiidae, Keroplatidae, and Mycetophilidae in part (Mycomyiinae, Sciophilinae, Gnoristinae and Leiinae), and Zaitzev (2003) -Mycetophilidae in part (Mycetophilinae and Manotinae). However, since many new taxa are added, and corrections, synonyms and revisions continually published, one needs a complete set of the fragmented taxonomic literature to cover all the species. A good source for obtaining most important literature on the Sciaroidea is the ViBrant/Scratchpad module Fungus Gnats Online (2014). Species identification of fungus gnats based on examination of larvae is currently impossible because the larvae seemingly lack unique morphological characteristics and search for species-specific molecular markers are yet to be implemented.
Fungus gnats are distributed all over the world with about 5,300 known species (Table 1), more than 1,450 of them are known from the Palaearctic region (Søli et al. 2000). According to the current version of the Fauna Europaea Web-database (Chandler 2004), 1,098 species of fungus gnats had then been recorded from Europe. Taking into account literature published subsequently these figures could be increased in ca 100 additional species, i.e. some 1,200 species are known in Europe at present. As opposed to many other insect groups, fungus gnats, at least Mycetophilidae, seem to display an increasing diversity towards the north in Europe, and in the European perspective, they are especially diverse in the boreal zone. The current version of the checklist of North European (Sweden, Norway, Finland, Russian Karelia, Russian Lapland, Denmark, The Faroes, and Iceland) fungus gnats (Kjaerandsen 2012) includes 896 species.
In Finland, 269 species of the fungus gnats (of which ca. 40 currently recognized species were described by Carl Lundström) were first listed in the Enumeration Insectorum Fenniae (Frey et al. 1941). Hackman (1980) presented the second checklist of Finnish Diptera that incorporates 486 species of fungus gnats including five with a question mark. This list of species, with minor additions and corrections concerning Mycetophilidae after systematical revisions of the genera Trichonta (Gagné 1981) and Mycomya (Väisänen 1984) in the Holarctic region was included into Catalogue of the Palaearctic Diptera (Hackman et al. 1988). During the recent two decades, large-scale inventories (e.g. Polevoi and Jakovlev 2004, 2014, Jakovlev and Penttinen 2007 have increased the total number of Finnish fungus gnats with ca. 300 species. The 2010 Finnish Red List assessment of fungus gnats was based on a regional species pool consisting on 734 species (Penttinen et al. 2010). At present, the Finnish fungus gnat fauna incorporates 767 recognized species (except Sciarosoma) and ca. 20 species awaiting descriptions. Altogether, 18 species names of wrong records from Finland were removed from the checklist. These species and 3 doubtful species names are listed in the end.