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Blera fallax

 
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stuart
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Joined: 11 May 2005
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Location: Peterborough, UK

PostPosted: Sat May 28, 2005 5:39 pm    Post subject: Blera fallax Reply with quote

Blera fallax (Linnaeus, 1758)

Identification ease/difficulty: 1

StatusHabitat indicator statusSources of information
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stuart
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Joined: 11 May 2005
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Location: Peterborough, UK

PostPosted: Sun May 29, 2005 8:40 am    Post subject: Species account from the Provisional atlas Reply with quote

Species account from Provisional atlas of British hoverflies, Ball & Morris, 2000.

Blera fallax (Linnaeus, 1758) Cynorrhina fallax Linnaeus in Coe (1953)

Biology: Larvae are associated with Pinus sylvestris in Scotland. A puparium has been found in a rot hole in a pine stump (Rotheray & Stuke, 1998). Larvae have subsequently been found in wet, heart-rot cavities in pine stumps. A single cavity may contain larvae of very mixed size, suggesting a larval period spanning several years. The adults are found in Pinus forest, and have been observed sunning themselves on trunks and flying about the base of large, live, native Pinus trees

Distribution: A very rare species of the Caledonian pine forest, with few recent records confined to Speyside. Old records, whilst still confined to the Speyside area of central Scotland, are more widespread, and some accounts around the turn of the century describe the species as “numerous”
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stuart
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PostPosted: Sun May 29, 2005 9:08 am    Post subject: Data sheet from Insect Red Data Book, Shirt, 1987 Reply with quote

Datasheet from the Insect Red Data Book, Shirt (1989).

Blera fallax[i] (L., 1758) ENDANGERED

Identification: Stubbs & Falk (1983), pp. 109 and 218, pl. 10.5.

Distribution: Historically in the main Caledonian pine forests of eastern Scotland, but currently only known at one site in the Spey Valley. The population is believed to be small.

Habitat and ecology: Mature or over-mature native pines[i]Pinus sylvestris
, and possibly deciduous trees, in Caledonian forest. An old observation of unknown source or reliability is of a female laying eggs in sap exuding from beech *and oak Quercus trees. Recent observations have been of adults sitting on live pine trunks and flying about the bases of such trunks where a thick mass of flakes of bark is exposed end-on at soil level. The hoverfly is related to genera which breed in dead wood, so it is possible that the larvae live between such pine-bark flakes and perhaps under similar circumstances about deciduous trees.

Status: It was formerly local but widespread in the pine-wwods of the eastern Highlands, but is now in danger of extincation. Its ecological requirements are unknown so it is difficult to cater for.Conservation: The one remaining known site is an RSPB reserve. Further survey is required to check on its biology and to find further populations.Threats: The loss of ancient trees through forest clearance and modern forestry practice in Scotland.

Author: A.E. Stubbs, using additional information from Coe (1953), G. Else and I. Perry (pers. comms).
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stuart
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Location: Peterborough, UK

PostPosted: Sun May 29, 2005 9:08 am    Post subject: Data sheet from National Review of Diptera, Falk, 1991 Reply with quote

Datasheet from the Review of Scarce and Threatened Diptera, Falk (1991).

BLERA FALLAX (Linnaeus) ENDANGERED

DISTRIBUTION Records are restricted to the major native pine forests of the Eastern Highlands of Scotland, almost exclusively along Speyside between Kingussie and Grantown on Spey, though with old records from Forres and Logie, Elgin (both 1902) and Braemar, Aberdeenshire (1873). The Loch Garten and surrounding areas of Abernethy forest may be its only surviving site today.

HABITAT Ancient coniferous woodland, as found in Caledonian pine forests.

ECOLOGY The larvae appear to develop in the dead wood of large post mature native pines and adults have been observed flying at the bases of such pines especially those with a thick mass of flaky bark exposed edge-on at ground level. A syrphid pupa, probably of this species was found beneath the loose bark of a fallen pine trunk at Loch Garten. Verrall (1901) cites a dubious observation of a female laying eggs in sap runs of oak and beech. Adults recorded from June to August and are said to be attracted to the flowers of wild raspberry and the stumps of cut pines.

STATUS Declining. Abernethy Forest is perhaps its only remaining population. This site is an NNR in part and the Loch Garten area is owned by the RSPB. There is no recent information from the Rothiemurchus or the Glen Feshie area, and the Grantown area where it was last recorded in 1943 is unlikely to support suitable habitat today.

THREAT Clearance of ancient Caledonian pine forest and especially of the old trees and dead wood within and replacement with modern forestry plantations which do not provide the old stumps or trees for larval development.

MANAGEMENT Ensure a future continuity of the dead wood resource required by this species by maximising the number of post mature trees within a site and retaining all stumps. Excessive deer grazing seems to be seriously hindering pine regeneration at some sites so that fencing areas or protection of young trees may be required. The maintainance of open glades may be necessary.
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