Cheilosia semifasciata (Becker, 1894)
Cheilosia fasciata Schiner and Egger in Coe (1953).
Biology & ecology:
The larva mines the leaves of Orpine Sedum telephium in southern England and Navelwort Umbilicus rupestris in North Wales. The resulting blotches are quite obvious. During its development the larva may occupy and vacate five of six leaves before it reaches maturity.
Although the food plants, especially Navelwort in North Wales, are widespread, C. semifasciata appears to be genuinely confined to North Wales and Shropshire with a few southern outliers. Numerous records from Shropshire arise from greatly increased recorder 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 most 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 & conservation:
The frequency of occurrence has varied considerably, probably due to bursts of activity by particular recorders. Recorded from 24 hectads since 1985.