DIPTERA REPORT 2022 PETER VINCENT
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 (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 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 to the 2000ha of coniferous 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
many insects as a result of climate change, C. piger maybe one of several mainland European dipterans heading this way. Additionally, we are witnessing many species increasing their range within Britain (e.g., Ball & Morris, 2021). The following species, Bombylius discolor Mikan, 1796 and Rhamphomyia marginata (Fabricius, 1787) were recorded in 2022, either for the first time in Suffolk or for the first time for a long while.
In last year’s Transactions (Part Four of Suffolk Diptera checklist), I stated that as far as I am aware there has been no recent records of the bee-fly B. discolor in Suffolk. The last appears to have been in 1941 in Monk Soham by Claude Morley. Stubbs & Drake (2001) suggested it had disappeared entirely from East Anglia, and the latest (Spring 2021) Newsletter of the Soldierflies and Allies Recording Scheme Bee-fly watch (Harvey, 2021) used iRecord data to show no sightings of B. discolor closer to Suffolk than Bedfordshire or Kent. Therefore, I was surprised to be contacted by Matthew Garnham who had recorded at least eleven of these flies at Elmsett, not least because their numbers suggest they have been there for at least a year or two.
B. discolor resembles B. major but has spotted wings rather than the dark B. major and the body is darker, a mix of chestnut and black. Females are very distinctive with a series of white spots down line of the abdomen. This is nantly a species of open habitats. As an early season fly (March to June, but most common in April) they feed on many spring flowers, especially ground-ivy Glechoma hederacea but also primrose Primula vulgaris, violets Viola sp and green alkanet Pentaglottis sempervirens. The larvae are parasitoids of spring-flying mining bee grubs and seem most strongly associated with Andrena flavipes Panzer, 1799 and A. cineraria (Linnaeus, 1758).
The first British record of the Empid Rhamphomyia marginata was in East Kent in 1973, where it became firmly established before recently extending its range through most of South East England and as far north as Norfolk (Jones, 2022). It was first recorded in Suffolk by Tim Hodge at Barton Mills on May 6th 2022. The females of R. marginata are one of the most distinctive of all British flies. They have extraordinary broadened wings, with a distinct dark brown band across the wing tips, giving a distinctly non-fly looking appearance. It is a spring flying species (late-April to early
June, peaking throughout May) and inhabiting rides in broadleaf, conifer and mixed woodland. This species is unusual, though not unique, as it is the females, and not the males, that swarm. Separate male and female swarms have been found but the ‘role reversal’ is the norm with marginata where females form swarms and males fly into them to select a mate. Swarming occurs particularly in the time before dusk (it has been found from late-afternoon to about 20.30).
In addition to species mentioned above, some interesting and uncommon species that have recently been recorded from Suffolk include, the Agromyzids, Cerodontha iridis (Hendel, 1927) and Phytomyza crassiseta Zetterstedt, 1860, the Anthomyiid, Pegomya cunicularia (see overleaf) (Rondani, 1866), the Chironomid, Synendotendipes impar (Meigen, 1818) [1st Suffolk record], the Drosophilid, Drosophila kuntzei Duda, 1924, the Fanniid, Piezura graminicola (see overleaf) (Zetterstedt, 1846), the Hybotid, Platypalpus leucocephalus (von Roser, 1840), the Milichiid, Phyllomyza securicornis Fallén, 1823, the Muscid, Aphaniosoma propinquans (Collin, 1949) [1st Suffolk record], the Mycetophilids, Grzegorzekia collaris (Meigen, 1818) and Sciophila pomacea Chandler, 2006, the Odiniid, Odinia trinotata Robineau-Desvoidy, 1830 [1st Suffolk record], the Periscelidid, Periscelis annulata (Fallén, 1813), the Piophilid, Stearibia nigriceps (Meigen, 1826), the Scatopsids, Anapausis nigripes (Zetterstedt, 1860) and Coboldia fuscipes (Meigen, 1830), the Tachinid, Tachina lurida (see overleaf) (Fabricius, 1781), the Tephritid, Oxyna flavipennis (Loew, 1844), and the Trixoscelidid, Trixoscelis canescens (Loew, 1865) [1st Suffolk record].
References
Ball, S.G. & Morris, R.K.A. (2021). Recent range expansion in British hoverflies (Diptera, Syrphidae). Dipterists Digest (second series) 28 (1): 59-87.
Harvey, M. (2021). Bee-fly watch 2020. Soldierflies and Allies Recording Scheme Newsletter 8: 7.
Jones, N. (2022). Rhamphomyia marginata (Empididae) on the move. Empid and Dolichopodid Newsletter 27: 2-3.
Stubbs, A. & Drake, C.M. (2001). British Soldierflies and their Allies. Reading, British Entomological and Natural History Society.
Stubbs, A. (2022). Flies. British Wildlife 33: 600-602.
Thornhill, A., Pennards, G.W.A. & Morris, R.K.A. (2022). Chalcosyrphus piger (Fabricius, 1794) (Diptera, Syrphidae) new to Britain. Dipterists Digest (second series) 29 (1): 84-86.
Peter Vincent
Pennyfields, Rectory Road, Middleton, Suffolk. IP17 3NW
