Scaeva pyrastri (Linnaeus, 1758)
Biology & ecology:
The larva feeds on a wide range of ground layer and (less frequently) arboreal aphids. Adults are often seen visiting flowers such as white umbels, and thistles Cirsium and Carduus spp. This is a migrant which reaches Britain around June from southern and central Europe, breeding here to give a generation in late summer. Although it is known to overwinter in central Europe, there is little evidence of this from western Europe suggesting that its annual occurrence is totally dependent on immigration (Speight, 2010). In Ireland and western Scotland, the earliest records are in July, suggesting that it is does not usually manage to breed in these areas.
Widespread in the lowlands of the southern half of Britain. In northern England and southern Scotland records are noticeably clustered along the east coast, as one might expect for a migrant species. It seems to be scarce in north and west Scotland, although it is recorded in Shetland. The numbers of records received vary greatly between years.
Status & conservation:
This is a migratory species which does not maintain a permanent population in Britain and therefore its frequency of occurrence varies greatly from year to year.