Cheilosia semifasciata Becker, 1894Nomenclature
Cheilosia fasciata Schiner and Egger in Coe (1953).Biology
The larva mines the leaves of Orpine Sedum telephium in southern England and Navelwort Umbilicus rupestris in North Wales and Shropshire. The resulting blotch-mines are quite obvious. During its development the larva may occupy and vacate five of six leaves before it reaches maturity. Adults fly rather early in the season, peaking in early May.Distribution
C. semifasciata appears to be genuinely confined to North Wales and Shropshire with a few southern outliers even though the foodplats, especially Navelwort, are very widely distributed. The numerous recent records from Shropshire arise from greatly increased recording effort. We cannot tell whether this represents a range extension or the recent discovery of a long-standing population. Searches of the food plant, even in areas where the species is known to occur, reveal that many apparently suitable patches are unoccupied. It seems likely that there are some very specific requirements that need to be met concerning the location and situation of the plant.Status
Lower Risk (Near Threatened) - Ball & Morris, 2010. Rare (RDB3) - Falk, 1991.