The conservation requirements of an endangered hoverfly, Hammerschmidtia ferruginea (Diptera, Syrphidae) in the British Isles
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The saprophagous larva of the endangered hoverfly, Hammerschmidtia ferruginea (Fallén, 1817) (Diptera, Syrphidae) develops in wet, decaying sap under the bark of dead trees and branches of aspen, Populus tremula L. (Saliaceae). However this breeding site is transient: wet decay builds up patchily over 1.5–2 years of the tree or branch dying and lasts for a further 1–3 years before the bark falls off. Between 1990 and 2006, H. ferruginea swung through a cycle of abundance when the number of localities where it was detected dropped from 13 to 5 and back to 8. Fluctuations in amounts of dead wood caused by winds and storms probably explain this population swing. When there are few dead trees and branches, H. ferruginea breeds in sap flows on live P. tremula trees and populations are maintained but at low levels. To prevent local extinctions during periods when fallen wood is scarce, breeding habitat can be supplemented by felling trees and branches. Fallen wood with wet decaying sap is also important as an assembly site for mate selection. Adult food plants include flowers of bird cherry Prunus padus, rowan Sorbus aucuparia and hawthorn Crategus monogyna. Adults were recorded dispersing up to 1 km but are probably able to move further than this.
KeywordsSaproxylic Populus tremula Distribution Breeding Mate seeking Food plants
We are very grateful to Peter Moore and Carl Mitchell of the RSPB for their continuous help and encouragement. We also thank RSPB and SNH for their financial support. We also acknowledge the considerable contributions over many years that members of the Malloch Society have made to this project, in particular, Geoff Hancock, Steve Hewitt, Dave Horsfield, David Robertson and Kenn Watt. We also thank Tom Prescott for his co-operation and active participation in H. ferruginea conservation while he was Warden at Insh Marshes NNR. Work on adult H. ferruginea ecology and behaviour was chiefly the responsibility of the senior author and she thanks her MSc supervisor, Dr. Graham Holloway at Reading University for his help and encouragement. In Finland GER and IM thank Dr. Gergo Varkonyi and in Russia to him and Dr. Boris Kashevarov for their help in arranging visits to boreal forest in their respective countries.
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