Species Account for Dioxyna bidentis
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Essex RDB: Listed
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Taxonomic group: flies (other) (Diptera: other groups) - County data
This picture-winged fly is a local species whose larvae feed on the flower heads and unripe seeds of the local Tripartite Bur-marigold Bidens tripartita, although it has been collected in areas where Bidens does not occur. Records are widely dispersed in England as far north as Yorkshire and with an old record from Kinrara, Speyside, Scotland (1936), but there are nine post 1960 sites known to Falk (1991a). Habitat preferences are unclear, but records include marshes and wet areas on commons and dunes. Threats include loss of the host plant through either overgrazing, or cessation of grazing with subsequent scrub invasion. Bidens species appear to require ground which is flooded in the winter, but not in the summer, (Falk, op. cit.) so it is essential that water levels facilitate this. References