SUFFOLK DIPTERA CHECKLIST
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DIPTERA REPORT 2018 PETER VINCENT The hot dry summer has done no favours for our flies and in my experience 2018 has been in general a poor one for insects. Our fly fauna suffers badly in major drought years; as when plants come under drought stress they produce less nectar for adult flies to feed upon and phytophagous species do not thrive when host plants wither and die. The many flies whose larvae require wet substrates struggle to complete their life cycle as wetland habitats dry out. As always there are winners and losers, some species have done well and appeared in reasonable numbers, but these are fewer than they should be. Although, not considered a positive thing in some peoples opinion, the house flies, Musca domestica Linnaeus, 1758 and M. autumnalis De Geer, 1776 seem to be in greater abundance this year. But some sage words on the state of British diptera, and perhaps by association the whole natural environment, at the current time was given by the prominent ecologist and dipterist Alan Stubbs commenting in British Wildlife magazine (Stubbs, 2018) ‘It is not all doom and gloom but the widespread feeling is that things are not what they used to be, even in good habitat’. Nevertheless, this year I am pleased to have received an increased number of queries and records from a larger number of Suffolk naturalists. Although physical voucher specimens are the gold standard in diptera identification, with modern digital cameras and technology it has never been easier to photograph living flies and I am pleased to accept records from photographs if they can be identified with certainty. Unfortunately many flies cannot be identified from images unless the critical features can be seen. David Fairhurst and Jamie Smith both sent me photographs of the spectacular Conopid Conops vesicularis Linnaeus, 1761 from Snape and Leiston respectively (Plate 5). This is the largest British Conops (body length 12-14mm) with a brown and yellow hornet-like appearance. It is a scarce species in Suffolk, although perhaps it will become more frequent as one of its host species the Hornet Vespa crabro Linnaeus, 1758 is becoming more frequent. Another, good Suffolk record was of the horsefly Atylotus latistriatus (Braeur, 1880) from Butley by Gary Lowe. All Atylotus species are restricted to narrow habitat types; A. latistriatus is a specialist saltmarsh species, recorded only in Suffolk from the Stour and Alde estuaries. In addition, I received specimens of the Drosophalid Cacoxenus indagator, from David Basham, that he had collected from the nest cells of the bee Osmia bicornis (Linnaeus, 1758) taken from his ‘bee hotel’. This fly is known to be a well known cleptoparasite of O. bicornis, but this is the first record from Suffolk, with apparently few records nationally. Another case of hymenopterists’ helping dipterists is Hawk Honey’s record of the Conopid Thecophora atra (Fabricius, 1775). Although, quite a common species, especially in the South of England, there are few records of T. atra from Suffolk. As I tend to collect material in the field during spring, summer and autumn and then spend time during the winter with my microscope identifying the flies I have collected, most of the records of flies I mention further into this report relate to 2017. Of most significance during this period was the discovery of Muscina pascuorum
Trans. Suffolk Nat. Soc. 54 (2018)