The Black Fungus Gnats (Diptera, Sciaridae) of Norway – Part I: species records published until December 2019, with an updated checklist

Abstract Black Fungus Gnats (Sciaridae) are a megadiverse, cosmopoliltan family of bibionomorph Diptera. Even in Europe, the continent with the longest tradition in sciarid taxonomy, numerous taxonomic issues remain unresolved and countless species await discovery and description. The fauna of Norway is in these respects no exception. Recognising considerable knowledge gaps, the Norwegian Biodiversity Information Centre provided substantial funding for a detailed inventory of the Sciaridae species occurring in Norway, which was realised in 2014–2018. The results of this project will be published in a series of papers, of which the first is presented here, summarising available data on the taxonomy, faunistics, and autecology of Norwegian Sciaridae beginning with Zetterstedt’s pioneering work in 1838 and ending with 31 December 2019 as the cut-off date. All published records from that period were analysed. The result is a list of 143 species and four unplaced names. Following a consistent scheme, verified locality details are provide including alternative spellings, habitats, and flight times of adults in Norway, literature citations for the faunistic records, and general taxonomic references for classification or identification. A checklist of the sciarid fauna of Norway and a complete list of the relevant literature are also presented.


Introduction
The Sciaridae is one of the largest families of Diptera, rich in both species and individuals, and plays a significant role in natural ecosystems (summarised in Menzel and Schulz 2007). For example, the larvae are important for the litter decomposition in forests (Hövemeyer 1989;Deleporte and Rouland 1991;Deleporte and Charrier 1996), and the adults for the transmission of basidiospores of fungi (Schmidt 1979) and the pollination of plants (Vogel and Martens 2000;Rulik et al. 2008). Sciarids are also well-known as pests in mushroom farms and greenhouses, or as common inhabitants of pot plants in houses (e.g., .
Often sciarids are one of the most dominant Diptera families in ecological studies (e.g., Thiede 1977;Feldmann 1992;Hövemeyer 1992;Bickel and Tasker 2004), and thousands of specimens can be collected in a short time (Menzel and Schulz 2007). Many species prefer moist, shady deciduous and coniferous woods with a high proportion of dead wood (Hövemeyer 1998(Hövemeyer , 1999(Hövemeyer , 2002Menzel and Schulz 2007). Other species can be found in wetlands (e.g., moist meadows, fens) or xerothermic habitats (e.g., dry grassland, heath) (Hövemeyer 1996;Heller 1998Heller , 2000. The Black Fungus Gnats (Figs 1-3) are inconspicuous, minute to medium-sized flies (0.8-7.0 mm body length) and are fairly uniform in appearance. While adults of most species are completely black or dark brown, others exhibit some yellow or orange. The head is relatively small and usually rounded, with the eyes meeting at a narrow bridge above the antennae. There are three ocelli on the forehead. The antennae are long and thin, with 16 segments. Of the mouthparts, which are generally inconspicuous, only the palpi are of relevance for taxonomy. The body is almost hairless at first glance. The wings are rather broad and rounded at the apex, often smoky-coloured, with a distinctively curved vein fork (M 1 +M 2 ) in the middle of the apex of wing. Females of some species have reduced wings (e.g., in Epidapus Haliday). The legs are long and slender, but not as long as for example in Mycetophilidae. The larvae are cylindrical, white and shiny, with a clearly sclerotised, dark head capsule. Detailed descriptions for the preimaginal stages and adults, and their importance for the identification and classification of sciarids, are given by  and Menzel and Smith (2017).
Compared to most other Diptera in Norway, Sciaridae have previously attracted little attention from entomologists. Notorious for their uniformity and small body size, adult sciarids are largely the domain of taxonomic specialists, while larvae of most species remain undiscovered. The earliest mention of Black Fungus Gnats in Norway was by Ramus (1735), who reported about the 'armyworm', a migration of thousands of sciarid larvae. However, the first taxonomic studies of Sciaridae in Norway are those of Zetterstedt (1838Zetterstedt ( -1860, Walker (1848), Siebke (1853Siebke ( -1877, and Holmgren (1869). Later, Edwards ( -1935, Lengersdorf (1926bLengersdorf ( -1930c, , Frey (1948), and Tuomikoski ( , 1967 contributed to the knowledge of the sciarid fauna of Norway. Some of these early records, but not all, were later treated in a modern review of the family . Relatively few recent studies exist, but notably Thunes et al. (2004), Hippa et al. (2010), Köhler et al. (2014),  (Zetterstedt, 1838) 2 brachypterous female of Corynoptera minima (Meigen, 1818) 3 apterous female of Epidapus gracilis (Walker, 1848). and Heller et al. (2016) have presented new and valuable information on the fauna of Norwegian Sciaridae. In 2014 the Norwegian Biodiversity Information Centre (NBIC) granted the project 'Sørgemygg i Norge' (Sciaridae of Norway) funding for the period 2014-2016. Later NBIC also granted funding for the project 'Sørgemygg i norske skoger' (Sciaridae in Norwegian forests), which is effectively the second phase of our research work. This ran from January 2017 to December 2018. Our study collates the records published between 1735 and 2019 and provides many corrected locality data for the Norwegian sciarid fauna. The revised nomenclature and the evaluation of faunistic records at species level form the basis for an updated checklist. For the first time, information is also summarised on the identified habitats and the phenology of species in Norway. Consequently, all results presented here comprise the published 'status quo', form the basis for the evaluation of our faunistic work in both mentioned NTI projects, and are the starting point for a series of papers on the Norwegian fauna. Many unpublished data on the Black Fungus Gnats of Norway, based on the identification of specimens in several museum collections, or on the samples collected by the authors between 2014 and 2018, shall be published in this series.

Material and methods
Norway, Europe's sixth largest country by land area, occupies approximately half of the Scandinavian Peninsula, bordering Sweden to the east, and Finland and Russia to the northeast (Fig. 4). The Norwegian mainland extends from 57.9 to 71.2N. The extensive coastline is dominated by many fjords and numerous islands, making it highly indented and irregular. The remote island of Jan Mayen (70.5-71.1N, 07.6-09.0E) and the archipelago of Svalbard comprising  and ) are also parts of the Kingdom of Norway.
All data analysed here were taken from both the scientific literature and publications in the media. They relate exclusively to the sciarid specimens recorded from Norway. The great total amount of data made it impossible for us to validate all the species identifications on which published records are based. To enable comparison with previous faunal lists, references to earlier records were added to the list and the synonymous names were given for each species.

Nomenclature and systematics
Employed nomenclature and systematics are mainly based on the revision of Palaearctic fauna , the revision of Nearctic fauna , and some works after 2000. These comprise Vilkamaa (2004, 2016) [Xylosciara, Claustropyga]; Hippa et al. (2003Hippa et al. ( , 2010 [Claustropyga, Corynoptera s. str.]; Vilkamaa and Menzel (2019) [Lycoriella, Hemineurina, Trichocoelina] and Vilkamaa et al. ( , 2013a [Dichopygina, Camptochaeta]. The proposal by Mohrig et al. (2017), who postulated Ctenosciara  as a junior synonym of Austrosciara Schmitz & Mjöberg, 1924, was not followed here, because the procedure used therein is contrary to the International Code of Zoological Nomenclature (ICZN 1999), and the type specimens of the type species have not yet been revised and compared. Some other nomenclatural problems at the species level are discussed at the appropriate places in 'Taxonomic notes'.

Presentation of data
All literature sources containing data and information on the Norwegian sciarid fauna are cited for each species under 'Faunistics'. Various outdated catalogues (e.g., Kertész 1902Kertész , 1903Gerbachevskaja-Pavluchenko 1986) were not evaluated because they do not contain primary data for the sciarid fauna of Norway and/or their abstracted and largely unverifiable content may lead to false results. In addition, in the category 'Taxonomy' publications are mentioned that are important for the classification, nomenclature and/or identification of the included sciarid species.
Locality data. Due to the geographical peculiarities, the Norwegian mainland with the offshore islands is treated first in the faunistic section on each species. Counties (fylke) and localities are listed in alphabetical order, unlike the traditional practice in lists of Norwegian fauna, which are arranged from south to north. Because the Arctic island of Jan Mayen and the Arctic archipelago of Svalbard are very remote from the Norwegian mainland, they are considered separately. Faunistic records for these islands are summarised in a separate block at the end of the locality lists, following the 'mainland records'. Geographic names are given in both modern Norwegian script and the spelling(s) used in the original literature, to facilitate their location in geographical maps and electronic resources. The reclassification of the Norwegian counties valid since 1 January 2020 was not taken into account here.
If available, all information about a locality is presented in a unified data structure as follows: Ecological data. If the literature sources provide information on habiat and/or temporal occurrence of a species, these data were summarised in an 'Ecological note'. All data published here refer exclusively to the Norwegian sciarid fauna. It should be noted that for most species the habitat requirements are poorly known or missing, so notes in this paragraph should be considered as incomplete. For example, the listing of a single habitat type does not necessarily mean that the species is only adapted to that habitat or that this information applies to all published Norwegian records and/or collected specimens. For many Norwegian species with few published data, no information currently exists on the habitat or the flight time of adults. Such 'negative results' of our literature study are indicated in the ecological notes of the species concerned by 'Habitat not specified' and/or 'Phenology: without data'.
Locality. • Norway; without further locality details (= 'Norway'). Faunistic note. The single Norwegian record of Bradysia angustipennis was published by  in a phylogenetic analysis (appendix 2) as 'Norway' without further locality details. The male specimen is deposited in the UZMH collection and was not revised here.
Ecological note. Habitat not specified. Phenology: without data.

Bradysia quercina
In the here presented checklist of Norwegian Sciaridae, Bradysia vagans (Winnertz, 1868) is missing, with its synonyms B. angustipennis Frey, 1948 [preocc.], B. callicera Frey, 1948 andB. richardi Gerbachevskaja, 1986. This is a very common species throughout Europe. It is dark brown, with rather broad wings and unicoloured dark-brown antennae, but is not distinguishable by the male genitalia from the reddish-yellow Bradysia rufescens (Zetterstedt). It is possible, that there are some misidentified specimens of Bradysia vagans (Winnertz) among the records of 'Bradysia rufescens', published before .
Ecological note. East-and South-facing mountainsides; on scree of steep slopes and on the tops of woody hillsides; eroded mountains with sandy areas at the foot; on steep slopes with large elms and valuable hardwood trees; mountain birch forests; forests along streams in otherwise muddy terrain; gardens with lawn and some larger trees. Phenology: May-Sep.  (2000), could not be found anymore in the UZMH collection (Vilkamaa, pers. comm.).

Discussion
In this literature review we document the knowledge on the Sciaridae of Norway accumulated up to 31 December 2019, which was basically the status quo before we started our nationwide taxonomic inventory funded by the NBIC. Nonetheless, data compiled here are the result of a meticulous study of the literature in the past six years, and thus a direct outcome of our NTI projects. History of data collection. The first mention of black fungus gnats in Norway was by Ramus (1735). In our literature study we evaluated 111 literature sources published during a period of 285 years (Fig. 5). Of these, 43 papers contain first records of species identified between 1838 and 2019 (Fig. 6). Most publications reported the occurrence of 'army worms' until the middle of the 19 th century and it was only with Zetterstedt (1838) that faunistic investigations began to be based on detailed Norwegian data at the species level. Of the 147 species now registered, the taxonomic status of four recorded by Zetterstedt (1838Zetterstedt ( , 1851Zetterstedt ( , 1855 is still unclear and these are treated here as doubtful species. Not surprisingly, knowledge about the composition of the Norwegian sciarid fauna did not increase continuously. Roughly three different time periods of taxonomic work can be distinguished (Fig. 6). The first period began with the work of Johann Wilhelm Zetterstedt (1785-1874), who described the first two Norwegian species in 1838. Later he published four additional books containing Norwegian records (Zetterstedt 1851(Zetterstedt , 1852(Zetterstedt , 1855(Zetterstedt , 1871. Other famous entomologists such as Francis Walker (1809-1874), Johan Heinrich Spalckhawer Siebke (1816Siebke ( -1875, August Emil Holm gren (1829-1888), and Wilhelm Maribo Schøyen (1844Schøyen ( -1918 also contributed to an inventory of the Norwegian fauna. After 51 years, 41 sciarid species were recorded, representing 28% of the currently known species inventory. After an intermission of over 35 years, the second period began in 1926. Between 1926and 1931Franz Len gersdorf (1880-1965 added 19 new records to the faunistic inventory. Shortly thereafter, in the timescale of taxonomic and faunistic studies, Tron Soot-Ryen (1896-1986 and the founder of modern sciarid taxonomy Risto Kalevi Tuomikoski (1911Tuomikoski ( -1989) recorded a further 17 species. Thus, in the second period, 36 species were recorded for the first time in Norway, representing a quarter of the known fauna. In the early 1990s, the number of publications and consequently the number of recorded species rose steeply. The increase was almost 86%, from 77 before 1990 to the current 143. The majority of these new records were provided by the dipterists Heikki Hippa, Frank Menzel, and Pekka Vilkamaa. For the closely related family Mycetophilidae (fungus gnats), Gammelmo and Søli (2006) described a similar curve of knowledge increase. Here, also, the beginning of the recording of the Norwegian fauna goes back to the middle of the 19 th century. Through several fundamental works by J.W. Zetterstedt and J.H.S. Siebke, Siebke (1877) was already able to list an inventory of 53 Norwegian species. After this period the Mycetophilidae received only little attention until a few publications appeared in the 1970s. This was followed in 1994 by a steep increase in faunistic knowledge, leading to more than 600 fungus gnat species having been recorded from Norway to date (see Gammelmo and Søli (2006), and subsequent papers). Records of approximately 200 additional species discovered in recent studies will soon be published (J. Kjaerandsen, pers. comm.).
Diversity in Northern Europe. It is obvious that the 143 species summarised here are only a part of the extant sciarid fauna in Norway. We know of numerous additional species that will be dealt with in subsequent publications, including many new to science. We anticipate that the number of species in Norway is at least similar to that in Finland (370) (Vilkamaa 2014, Salmela et al. 2015, Hippa and Vilkamaa 2016, Vilkamaa and Menzel 2019 and Sweden (299) (Heller et al. 2009(Heller et al. , 2016Heller and Menzel 2013;Vilkamaa et al. 2013a-c;Vilkamaa and Menzel 2019), although the inventory for Sweden in particular is highly incomplete (Menzel et al. 2020). Even so, the results of our projects should not be regarded as exhaustive; there are still large areas, including very promising habitats, in which sciarids remain poorly sampled or have not been collected at all. Also, as the senior author's experience with the German fauna (more than 650 species) has shown, the high proportion of rare, or rarely collected, species makes it impossible to achieve a comprehensive inventory during a study period of only five years. Due to the diversity of landscape structures, climate conditions, and habitats, the number of sciarid species in Norway, including the Arctic islands, must be 20% higher than that in Sweden and Finland. Consequently, knowledge on the black fungus gnats in Norway summarised here is still incomplete and represents only 30% of the estimated inventory of ca. 450-500 species. The numbers mentioned above are an indication that we are still far from having a complete knowledge of sciarid diversity in Scandinavia, and that extensive research will be needed in the future.

Distribution and phenology in Norway.
A rough summary of recorded species by mainland counties south and north of the Arctic Circle, including the offshore islands (Fig. 7) shows that a majority of 83 species were found in southern Norway while the northern mainland supports 74 species. The known species inventory of the Arctic islands ranges from three (Jan Mayen) to 13 (Spitsbergen). Our literature survey shows that some species are very common and widely distributed on the Norwegian mainland (e.g., Bradysia nitidicollis, B. rufescens, Ctenosciara hyalipennis, Lycoriella ingenua, Scatopsciara atomaria, Sc. vitripennis), similar to the situation in other European countries. Some species not only inhabit the entire mainland, but also reach the arctic islands (e.g., Bradysia nervosa, B. praecox). In addition, there are also species with a relatively large number of records, which are apparently adapted to a harsh climate with a short vegetation-growth period. These species (e.g., Camptochaeta consimilis, Cam. delicata, Schwenckfeldina tridentata, Trichocoelina cochleata and Trichoc. vitticollis) were only found in the far north (Troms, Finnmark) and/or on the Arctic islands of Jan Mayen, Bjørnøya and Spitsbergen. On the other hand, several species seem to occur only in southern Norway (e.g., Cratyna uliginosoides, Sciara hemerobioides, Trichosia lengersdorfi). The areas south of the Arctic Circle in particular have not been sufficiently investigated. At least 350 sciarid species are expected in southern Norway including the high mountains. By contrast, the number of species on the Arctic islands will be probably increase only slightly (up to 20).
The very species-rich genera Bradysia Winnertz, Corynoptera Winnertz and Scatopsciara Edwards are still largely underrepresented in the papers published so far (see checklist). Many Holarctic species of the genera Claustropyga Hippa, Vilkamaa & Mohrig, Hemineurina Frey, and Lycoriella Frey are also still missing. Only one or two species of Epidapus Haliday, Dolichosciara Tuomikoski and Pseudolycoriella Menzel and Mohrig have been reported from Norway so far. The genera Cosmosciara Frey, Hyperlasion Schmitz, Phytosciara Frey, Prosciara Frey, Pnyxia Johannsen, Pnyxiopsis Tuomikoski, Scythropochroa Enderlein and Stenacanthella Vilkamaa and Menzel are not known yet from Norway. They were recorded from many countries in central and northern Europe, mostly with few species, and may also be present in Norway.
According to all literature sources, sciarids were found from March to October with a clear peak in July (Fig. 8). However, this is far from providing a realistic picture of the phenology. Together with the higher 'accumulation of species' in June and August, it reflects the preferred collecting period of entomologists in the summer rather than the actual phenology of Sciaridae. The sciarid records considered here are mostly from by-catches, whereas targeted long-term studies carried out with standardised trapping methods over several years in the same habitat type in Norway have not yet been undertaken. Thiede (1977) and Feldmann (1992), for example, studied the emergence times and activity patterns of sciarids over a two to three year period in selected beech, spruce and pine forests in Germany. They found that sciarid phenology can vary significantly between studied forest ecosystems based on the species identified. Under temperate climatic conditions (e.g., in Central Europe) adults usually have two activity phases: mid-March to early June and early August to late September, with two peaks in April and September. Depending on precipitation and temperature, the first peak may shift to March or May and the second peak to June/July or October/November. Numerous ecological studies have shown that some species complete two generations per year in Central Europe, in spring and late summer or autumn. Other species are univoltine, with only one generation in spring, summer or late summer (Thiede 1977). Unfortunately, data on Norwegian sciarids are still too sparse for a solid evaluation. Some common species are present from spring to autumn, similar to those in Central Europe (e.g., Bradysia nitidicollis, Cratyna uliginosa, Cr. uliginosoides, Lycoriella ingenua, Scatopsciara atomaria, Scatopsciara vitripennis, Trichosia lengersdorfi). In southern Norway some species could be bivoltine (e.g., Bradysia iridipennis, Trichosia caudata). It is to be expected for Norway that the phenologies of species adapted to temperate habitats will differ clearly from those of subpolar sites. The period of adult activity probably shortens significantly with increasing northern latitude, shifting to the summer months of June to August due to the short vegetation-growth period in the far north and Arctic islands (e.g. Camptochaeta consimilis, C. delicata, Trichocoelina vitticollis).
Outlook. The Sciaridae is still one of the most poorly studied families of Diptera in Norway, especially in the interior of the country, which is mostly unexplored. The life history of most Norwegian sciarid species (including immature stages and life cycles) are largely unknown. In addition, at present only little information exists on habitat preferences of the northern European species, especially those with a subarctic and arctic distribution. As a consequence, the family was not included in the new Red List for Norway (Gammelmo et al. 2015). Knowledge on Sciaridae at the species level is important for understanding the complexity of terrestrial ecosystems, in particular woodland decomposition processes. The first step in establishing such knowledge must be to determine which species occur in Norway and in which habitats they thrive.
The above-mentioned NTI projects (including the present study) aimed to survey sciarids that are found in the wide array of natural habitats in Norway and in the 'Natur i Norge' (NiN) system. Another objective is to provide the Norwegian scientific community with tools for identifying Norwegian sciarids, including identification keys, reference collections and genetic resources. Both projects will also contribute to global biodiversity initiatives by providing data on species occurrence, genetic diversity and geographic distribution. Knowledge on the sciarid fauna in Norway is thus expected to increase considerably in the next few years. Continuous collecting efforts and taxonomic studies will provide a solid new base of knowledge on Sciaridae in Norway. Finally, we hope that the present study will contribute to a better understanding of an interesting insect group and close existing gaps of knowledge in biodiversity research, especially on the sciarid fauna of Scandinavia.
Tromsø, Norway), Prof. Dr Geir E.E. Søli (NHMO, Oslo, Norway), Dr Pekka Vilkamaa (UZMH, Helsinki, Finland), and Dr Karl H. Thunes (NIBR, Ås, Norway). They provided us with samples in alcohol, loaned Norwegian sciarid specimens, provided various information about the collections included, or looked after FM and AK during the working stays at the museums in Helsinki, Tromsø, and Trondheim. We are also indebted to Andrew Liston (SDEI, Müncheberg, Germany) for checking the English.