This widespread and common hoverfly is a bumblebee mimic, taking on different colour forms to match various bumble bees. It is characterised by the strong projection on the hind femur, which gives it a thickened appearance.
In spring, the males are seen flying low and hovering over short grass looking for a female. She lays eggs near bulbs, especially wild bluebells and daffodils, and larvae then enter and feed on the bulb. The adults may be seen in a greenhouse from February and outdoors from April to August.
The adults feed on pollen and nectar of spring flowers, especially dandelion. The larvae burrow into bulbs of bluebells and other plants.
I found the pupae emerging right beneath a stand of bluebells. This does not make me happy as at least half the plants in my front yard are some form of bulb or other.