SUFFOLK DIPTERA CHECKLIST
67
As we all know, the summer of 2022 was hot and perhaps more significantly for flies, dry. A series of hot and dry summers in the last decade has meant a substantial deterioration in habitat quality. Wetlands are drying out, and whether this be streams and rivers, pools, ponds, ditches, seepages or springs, there are less wet places than there used to be or that there should be. Unfortunately, Suffolk’s fly fauna is not adapted to these conditions and they are in trouble. Many species of fly have aquatic or sub-aquatic larvae, or at least larvae that depend on wet or moist soils and rotting vegetation. Well known groups such as hoverflies and craneflies that are not normally associated with wetland habitats, but have larvae whose development depends on moisture, are showing drastic declines in numbers across the country (Stubbs, 2022). As I noted in the 2021 diptera report, although hoverflies are the most studied and recorded family of flies in Suffolk - with about 180 of the 280 British species known from the county - new species continue to be added to the Suffolk checklist. This again was shown to be the case when Alan Thornhill photographed a conspicuous red and black hoverfly at West Stow Country Park on the 3 July 2021. Alan was unsure of its identity but following investigation he suspected it to be Chalcosyrphus piger (Fabricius, 1794), a species yet to be recorded in Britain. He posted photographs of the fly on the UK Hoverflies Facebook group that were seen by Gerrard Pennards, a prominent Dutch expert on Syrphids, who confirmed the fly to indeed be of C. piger, a distinctive European species (Thornhill, Pennards & Morris, 2022). Coniferous woodlands seem to be the preferred habitat of C. piger with larval biology associated with larch Larix sp and pines Pinus sp. Further investigation would be needed to confirm if this was a one-off sighting or if a population of C. piger has become established in the area. The proximity of West Stow Country Park Chalcosyrphus piger West Stow Country Park, to the 2000ha of coniferous 3 July 2021. woodland in the Kings Forest does mean that there is plenty of potential breeding habitat close by. It is always a matter of conjecture of when and how new species arrive in Britain, but Suffolk laying just across the North Sea from continental Europe is well placed to receive any new migrants. With the well documented northern range expansion of
Trans. Suffolk Nat. Soc. 58 (2022)
Alan Thornhill
DIPTERA REPORT 2022 PETER VINCENT