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There is no clear pattern to the losses. Those in East Anglia and the Welsh Marches were largely before 1930, and those since are throughout the range. A study in 2004 covering Dorset, Hampshire and Sussex confirmed only small losses at a hectad level, but dramatic declines at tetrad, and even more at 1km level. A definitive map showing the number of tetrads per hectads would be a great help.
There is also no clear reason for the losses, though denser woodland, more overgrown woodland edges as well as losses to coniferisation and changes in management of quarries and verges are all reported as causes of loss. Some sites have been lost from drainage of fens. It is interesting that most of the other widespread woodland orchids, including Cephalanthera damasonium, Neottia nidus-avis and Platanthera chlorantha, are also listed on the Red List for the first time. Notes and possible resons for decline are in Edwards & Pearman (2004) and Sanford (1991). Furthermore other woodland edge plants, such as Campanula patula, Fallopia dumetorum and Melittis melissophylum have also dramatically declined, demonstrating that, in the writer’s view, this is one of the most threatened habitats in Britain.
There is anecdotal but no hard evidence for some decline in mainland Europe.
Ecology
A shade-tolerant tuberous herb usually found on chalk and limestone soils, and, like many orchids, sporadic in its appearance. In the south of England it is usually found in open deciduous woodland and scrub, but also recorded from denser shade, especially in beech woods. In woodlands it may grow with other orchids, such as Cephalanthera damasonium, Neottia nidus-avis, Orchis mascula and Platanthera chlorantha, and is included in the NVC community W12. On wood edges it grows in CG communites.
More rarely, but increasingly further north it is found in calcareous grassland, chalk-pits, limestone pavement, disused railways, spoil heaps and, rarely, unstable coastal cliffs, reaching its northerly limit on limestone slopes scree? in Cumbria (Foley & Clarke 2005). Interestingly Irish and populations are confined to open calcareous flushes and fens (M13, M13b) very unlike its habitats in England. It still survives at least one similar site on Anglesey (Cors Bodeilio) where it grows on Schoenus tussocks within species-rich fen (I. Bonner, pers. comm.). See Roberts (1958) for details of this remarkable habitat.
The Fly Orchid is not very slowgrowing, but it does not easily colonise new sites. This may be partly due to low seed production. (Sanford 1991). The flowers are visited by wasps, but pollination is often haphazard, with as few as 20% of flowers with mature seed (Foley & Clarke 2005). Flowering often starts in May in the south, though this can continue till July, especially further north.
The limitations of such a finely tuned pollination mechanism may become increased, as solitary wasps are also becoming scarce, due to habitat loss (Sanford 1991).
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