[reference: Dipterist's Digest (Second Series) 2002 Vol. 9 No. 1]
Chris Raper†
and Matthew Smith*
†[postal address withheld] Email:
chris.raper@tachinidae.org.uk
*[postal address withheld] Email: matt.smith@tachinid.org.uk
Records detailing a new British site for Cistogaster globosa (Fabricius, 1775) and Phasia barbifrons (Girschner, 1887) are given, together with a note of their current British distribution.
In 2001 Thames Water plc commissioned entomological surveys covering several of their sites. Fieldwork was undertaken by Martin Townsend and insects from a range of orders were collected by a variety of methods including sweeping, hand netting and Mercury Vapour light trapping. Initial sorting of the Diptera to family level was undertaken by John Ismay at Oxford University Museum, with the Tachinidae being passed to CR for identification to species.
One of the sites surveyed was Speen Reservoir near Newbury in Berkshire (SU4667, VC 22). This site is adjacent to the River Kennet and comprises a mixture of rank, marshy vegetation which floods in winter, together with areas of drier, ungrazed calcareous/neutral grassland. Tachinid flies identified from a sample taken on 14 August 2001 included specimens of Cistogaster globosa (Fabricius, 1775) (1 female) and Phasia barbifrons (Girschner, 1887) (2 females).
Cistogaster globosa is a parasitoid of shieldbugs of the genus Aelia (Hemiptera, Pentatomidae) and has been reared from Aelia acuminata Linnaeus, A.rostrata Boheman and A. sibirica Reuter. Of these, only A. acuminata is known from Britain. C. globosa (as Gymnosoma) was allocated RDB 1 status in Shirt (1987) and Falk (1991). The most recent review (Falk and Pont, in preparation) has provisionally accorded the species RDB 2 status. In the warmer parts of central Europe it is apparently taken quite commonly (Tschorsnig & Herting 1994), though the species has always been very local in Britain. The few records known to the Tachinid Recording Scheme come from scattered sites in southern England and Wales, with the fly appearing to favour dry grassland habitats where its hosts are predominantly found. Speen Reservoir is a new site for this species.
Phasia barbifrons was added to the British list on the basis of specimens collected in Kent and Surrey (Clemons 2001), with further records coming from Surrey in 2001 (Chandler 2001). The Tachinid Recording Scheme currently has records of this species from eight sites in Kent and Surrey. Speen Reservoir is the first Berkshire record for the species and the most westerly British location known to date. Identification of P. barbifrons may pose a problem as it is not included in the current RES key (Belshaw 1993) and may therefore be overlooked. Clemons (2001) provides a modification to the Phasia key in Belshaw (1993), which will allow identification of the species, and the species is covered in the Central European Tachinidae key by Tschorsnig & Herting (1994).
The authors would like to thank Thames Water plc and Martin Townsend for giving permission to publish these records.
Belshaw, R. 1993. Tachinid flies. Diptera: Tachinidae. Handbooks for the identification of British Insects. 10 4a(i). 169pp. Royal Entomological Society, London .
Chandler, P. 2001. Phasia barbifrons (Girschner, 1887) (Diptera, Tachinidae) at a second Surrey site. Dipterists Digest (Second Series) 8: 131.
Clemons, L. 2001. Phasia (Phasia) barbifrons (Girschner, 1887) (Diptera, Tachinidae), a possibly overlooked species new to Britain. Dipterists Digest (Second Series) 8: 3-5.
Falk, S. 1991. A review of the scarce and threatened flies of Great Britain (Part 1). Research and Survey in Nature Conservation 39. Peterborough, Nature Conservancy Council.
Falk, S.J. & Pont, A.C. (in preparation). A review of the scarce and threatened flies of Great Britain: Calyptratae. UK Nature Conservation Series. Peterborough, Joint Nature Conservation Committee.
Shirt, D.B. [Ed]. 1987. British Red Data Books: 2. Insects. Peterborough, Nature Conservancy Council.
Tschorsnig, H.P. and B. Herting. 1994. Die Raupenfliegen (Diptera: Tachinidae) Mitteleuropas: Bestimmungstabellen und Angaben zur Verbreitung und Ökologie der einzelnen Arten. Stuttgarter Beitrage zur Naturkunde. Serie A (Biologie) 506, 170 pp.