Cheilosia albipila Meigen, 1838
Biology & ecology:
The larva tunnels the stems of Marsh Thistle Cirsium palustre and some other thistles. It does not cause the plant to develop multiple stems but may cause stems to thicken. The larvae leave the stem and pupate in the soil nearby, usually in mid-summer. Adults visit early spring-flowering shrubs such as Sallows Salix and females can occasionally be found sitting on Marsh Thistle rosettes.
This is a very widely distributed species that will probably prove to be more widespread than current records suggest. Our experience suggests that most upland sites in Scotland that support Marsh Thistle will yield this hoverfly if sought as larvae.
Status & conservation:
There has been a sharp decline in occurrence over the past 35 years across much of Britain, especially south-east England; however numbers of records have been stable in upland areas where more dedicated recorder effort has been concentrated. This may mean that any lowland decline reflects changing levels of recorder competency.