Biologia 72/1: 62—69, 2017 Section Zoology DOI: 10.1515/biolog-2017-0007 The rediscovery of Orthoceratium lacustre (Scopoli, 1763) (Diptera: Dolichopodidae) in Belgium, with data on its ecology and distribution in the Palaearctic region Marc Pollet 1,2,3 , Anja De Braekeleer 1 , Christopher Martin Drake 4 & Frank Van de Meutter 1 1 Research Institute for Nature and Forest (INBO), Kliniekstraat 25, B-1070 Brussels, Belgium; e-mail: mpollet.doli@gmail.com 2 Research Group Terrestrial Ecology (TEREC), Ghent University, K.L.Ledeganckstraat 35, B-9000 Ghent, Belgium 3 Entomology Unit, Royal Belgian Institute for Natural Sciences (RBINS), Vautierstraat 29, B-1000 Brussels, Belgium 4 Orchid House, Burridge, Axminster, Devon EX13 7DF, United Kingdom Abstract: Upon recent rediscovery of the dolichopodid Orthoceratium lacustre (Diptera: Dolichopodidae) in Flanders (northern Belgium) three sites with potential habitat of the species in Flanders were visited in September 2016. The survey revealed the presence of a population of the species at each site. In order to explain its apparent absence in Flanders for nearly the past 40 years, information on the distribution, ecology, phenology and conservation status of the species was gathered from the literature and available data sets and databases. O. lacustre has a western Palaearctic distribution and occurs in northwestern Europe, the Mediterranean basin and the Middle-East. It clearly prefers coastal salt marshes and brackish marshes in the first region, but also occurs near open water in forests at higher altitudes in the two latter regions. Whereas it reaches its activity peak in September in northwestern Europe, its main activity is situated at least two months earlier in the southern part of its distribution range. It is considered very rare in both Flanders and the Netherlands, nationally scarce in Great Britain, and currently extinct in Germany. A very strict habitat affinity, unusual phenology and/or effects of collecting methods seem responsible for its previous Red list status as ‘extinct in Flanders’. Key words: Palaearctic Realm; Europe; Dolichopodidae; Red List; nature conservation; ecology; phenology Introduction The dolichopodid fly Orthoceratium lacustre (Scopoli, 1763) (Fig. 1) has always been an iconic species: it is rather large (5–6.5 mm) compared to other dolichopo- did species, conspicuous with a brilliantly metallic olive green body, and it had been known from only one lo- cality in Belgium where it had been collected for the last time in 1978. As a result, the species was con- sidered “extinct in Flanders” by Pollet (2000). Great was MP (M. Pollet)’s astonishment when FvdM (F. Van de Meutter) recently handed over a sample he collected north of Dudzele (prov. West Vlaanderen) in 2012 which comprised three specimens of this species. Not only did their presence surprise MP, but also the late date of the sample (19 October) and the fact that this site was well beyond the historic capture locality of the species! From the literature O. lacustre is described as a littoral species of coastal salt marshes (Parent 1938; Beschovski 1971; Meuffels 1981; Clemons 2003), and al- though this habitat type had been occasionally inves- tigated in the past forty years in Belgium, this species had not even been collected once since 1978. In order to learn more about both the distribu- Fig. 1. Orthoceratium lacustre, male (photo Rui Andrade). tion and the habitat requirements of this species and the reasons why it has been overlooked for nearly forty years, a small scale survey in Belgium was conducted together with a literature study and an analysis of pri- vate databases. This paper presents the results. c 2017 Institute of Zoology, Slovak Academy of Sciences Brought to you by | University of Sussex Library Authenticated Download Date | 2/25/17 11:56 AM