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DIPTERA REPORT 2019 PETER VINCENT I am starting this Diptera report with some disturbing observations on the catastrophic fall in global insect populations as well as on some more specific research concerning the decline of pollinating insects in Britain. A report was published earlier this year which gained headlines across the media. It was a comprehensive review of 73 historical research papers on insect declines from across the globe; the conclusion of which was that 40% of insects may become extinct over the next few decades. The main drivers of species declines appear to be in order of importance: i) habitat loss and conversion to intensive agriculture and urbanisation; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change (Sånchez-Bayo & Wyckhuys, 2019). Despite this paper being one of the most comprehensive analyses of the state of the world's insect populations it still contains substantial gaps. This is because not all insect groups have been studied equally; one order that is frequently overlooked is Diptera. Diptera have often been ignored, primarily because they are difficult to study. It is often hard to identify the species both from the larval and adult stages, especially compared to other groups such as moths and butterflies. The enormous biomass of flies supports a whole range of other animal groups, particularly the more traditionally charismatic birds and bats. This makes the fact that so little is officially known about the number and population trends of flies all the more concerning. The Diptera, which include everything from houseflies and hoverflies to midges and mosquitoes, are hugely important due to their sheer numbers, but they are also significant contributors to most ecological functions such as pollination. Some work is now being done, especially into the decline of economically pollinating flies. A recent paper that comments on declines in pollinating insects in Britain, uses occupancy models for 353 wild bee and hoverfly species between 1980 and 2013 (Powney et al., 2019). They found that in both hoverflies and bees a third of species assessed declined in range, while just a tenth increased their geographic distribution. Furthermore, they estimated a staggering net loss of over 2.7 million occupied 1 km2 grid cells across all species. Rates of distribution declines were similar for bees and hoverflies (25% and 24% respectively), although declines in pollinator evenness suggest that losses were concentrated in rare species. Finally, on pollinating hoverflies, some fascinating research into mass migration by hoverflies using insect monitoring radars revealed that up to 4 billion hoverflies (80 tonnes of biomass) travel high above southern and eastern Britain each year on seasonal migrations. These hoverflies transport billions of grains of pollen between Europe and Britain and locally produced populations consume some 6 trillion aphids and make billions of flower visits (Wooton, et al. 2019). Undoubtedly, a highlight was the discovery of the Conopid fly Leopoldius calceatus (Rondani, 1857) by David Basham at Purdis Heath near Ipswich. Although, the fly was found in 2018, details have only recently been published (Clements & Basham, 2019). This record of L. calceatus is considered new to the British Isles. Of the six species of
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P. Kitchener
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Leopoldius calceatus mating pair at Shottisham, 5 October 2019. Leopoldius found on the near continent L. calceatus is considered rather a rare species, confined mainly to central, eastern and southern Europe. Nevertheless, on the 5 October 2018 this species was caught at a moth-trap; the specimen, thought to be a female, was photographed but not retained and the photographs posted on the Facebook ‘Conopids’ page. The photographs were sufficient to allow a positive identification, initially by John Smit of EIS Kenniscentrum, Leiden and later by David Clements (Dipterists Forum Conopid Recording Scheme Organiser), through comparison with reference photographs. Subsequent surveys in the days following the identification of the specimen did not yield any further examples, although a male of L. signatus (Wiedemann, 1824) was also obtained at a moth trap at the same location on the 12 October 2018. There is always conjecture about the origin of such rare but conspicuous species as L. calceatus. It seems unlikely that such an eye-catching insect would remain undetected in Britain until now, although perhaps not impossible, as it does fly very late in the season and is evidently a rare species which tends to occur at very low densities in the rest of Europe. On the other hand, the specimen could have easily arrived as a stowaway on some passing vehicle. Colonisation by natural means is also likely, as mentioned earlier in this article billions of similar sized hoverflies regularly cross into Britain from mainland Europe and the nearest parts of Belgium and the Netherlands lie only about 150km across the North Sea. However, speculation around the origins of L. calceatus in Suffolk deepened, when amazingly Paul Kitchener managed to photograph a mating pair at Shottisham on the 5 October 2019. So we
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now know that there is most likely to be a small population of L. calceatus in Suffolk, but questions still remain about how long it has been here. Is it a recent arrival perhaps driven by climate change, or has there always been a dispersed but hitherto undetected population? Perhaps time will tell. In August 2019 David Basham collected another rare Conopid fly, Myopa fasciata Meigen, 1804, from Purdis Heath. This possibly constitutes a new county record. M. fasciata is a scarce and possibly declining species of southern lowland heathland, with records concentrated within Dorset, the New Forest, West Sussex and Surrey plus a few outliers extending as far north as Norfolk. The mining bee Andrena Myopa fasciata fuscipes (Kirby, 1802) is the main host. Another surprising record was of Oestrus ovis Linnaeus, 1758 - the Sheep Nostril Fly by Hawk Honey from the Suffolk Wildlife Trust reserve at Lackford Lakes. O. ovis used to be widespread in the southern half of Britain but is rarely recorded today and is graded Near Threatened in Falk & Pont (2017) - Natural England Calypterate status review. Finally, Rachispoda breviceps (Stenhammar, 1885) has been reinstated as a British species following the confirmation of 11 specimens from three sites across East Anglia, including Cavenham Heath (Brice & Perry, 2018). In addition to species mentioned above, some interesting and uncommon Suffolk species I have recently recorded include, the Agromyzid, Cerodontha luctuosa (Meigen, 1830), the Anthomyiids, Botanophila brunneilinea (Zetterstedt, 1845), Chirosia albitarsis (Zetterstedt, 1845), Delia criniventris (Zetterstedt, 1860), D. lamelliseta (Stein, 1900), Egle subarctica Huckett, 1965, Fucellia maritima (Haliday in Curtis, 1837), Leucophora personata (Collin, 1921), Paradelia intersecta (Meigen, 1826), and Pegoplata annulata (Pandell, 1899), the Camillid, Camilla flavicauda Duda, 1922, the Chloropids, Elachiptera tuberculifera (Corti, 1909), Meromyza femorata Macquart, 1835, Oscinisoma cognatum (Meigen, 1830), and Tricimba cincta (Meigen, 1830), the Dolichopodids, Chrysotus blepharosceles Kowarz, 1874, C. laesus (Wiedemann, 1817), Diaphorus oculatus (Fallén, 1823), and Hydrophorus bipunctatus (Lehmann, 1822), the Drosophilids, Acletoxenus formosus (Loew, 1864) and Drosophila hydei Sturtevant, 1921, the Empidids, Dolichocephala guttata (Haliday, 1833) and Hilara thoracica Macquart, 1827, the Ephydrid, Discomyza incurva (Fallén, 1823), the Fanniids, Fannia genualis (Stein, 1895), F. lucidula (Zetterstedt, 1860), F. manicata (Meigen, 1826), and F. monilis (Haliday in Curtis, 1837), the Heleomyzid, Tephrochlamys flavipes (Zetterstedt, [1838]), the Hybotids, Crossopalpus nigritellus (Zetterstedt, 1842), Drapetis ephippiata (Fallén, 1815) and Platypalpus cursitans (Fabricius, 1775), the Muscids, Haematobia irritans (Linnaeus, 1758), Haematobosca stimulans (Meigen, 1824), Hydrotaea armipes (Fallén, 1825), and Polietes lardarius (Fabricius, 1781), the Pallopterids, Palloptera trimacula (Meigen, 1826) and P. umbellatarum (Fabricius, 1775), the Sarcophagids, Sarcophaga melanura Meigen, 1826 and S. nigriventris Meigen, 1826, the Scatopsids, Reichertella geniculata (Zetterstedt, 1850) and
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Swammerdamella brevicornis (Meigen, 1830), the Tachinids, Catharosia pygmaea (Fallén, 1815) and Linnaemya picta (Meigen, 1824), the Tephritids, Acanthiophilus helianthi (Rossi, 1794), Acidia cognata (Wiedemann, 1817), Chaetorellia jaceae (Robineau-Desvoidy, 1830), and Merzomyia westermanni (Meigen, 1826) and the Tipulid, Tipula submarmorata Schummel, 1833. References Brice, D. & Perry, I. (2018). Rachispoda breviceps (Stenhammar, 1885) (Diptera, Sphaeroceridae) reinstated as a British species. Dipterists Digest (second series) 25: 171–172. Clements, D.K. & Basham, D. (2019). Leopoldius calceatus (Rondani) (Diptera, Conopidae) new to Britain. Dipterists Digest (second series) 25: 193–196. Falk, S.J & Pont, A.C. (2017). A Provisional Assessment of the Status of Calypterate flies in the UK. Natural England. Commissioned Reports 234. Powney, G.D., Carvell, C., Edwards, M., Morris, R.K.A., Roy, H.E., Woodcock, B.A. & Issac, N.J.B. (2019). Widespread losses of pollinating insects in Britain. Nature Communications 10: 1018. Sánchez-Bayo, F. & Wyckhuys, K.A.G. (2019) Worldwide decline of the entomofauna: A review of its drivers. Biological Conservation 232: 8–37. Wotton, K.R., Gao, B., Menz, M.H.M., Morris, R.K.A., Ball, S.G., Lim, K.S., Reynolds, D.R., Hu, G. & Chapman, J.W. (2019) Mass seasonal migrations of hoverflies provide extensive pollination and crop protection services. Current Biology 29 (13): 2167–2173. Peter Vincent Pennyfields Rectory Road Middleton Suffolk IP17 3NW
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