The drone fly (Eristalis tenax) is one of our most common insects and yet one of our most unrecognised. As its nick-name, drone, suggests it is an exceptionally effective mimic of the male hive bee or drone but it is, in fact, a hoverfly. This insect is one of the first to be seen in early spring and one of the last to disappear in the late Autumn. Adults hibernate in any suitable outdoor crevice and they can emerge on any reasonable day that might occur, even in winter. They are intensely inquisitive and will approach you in the garden and hover in front of you taking a good look before darting off in another direction. They are completely harmless of course.
The larva, the red-tailed maggot, lives in water courses (rivers, drains, etc) that are polluted by organically rich run-off from dung, silage and other farm substances. The numbers of these flies will be greater near farms but they quickly spread out and can be seen almost anywhere. They are most plentiful in spring and autumn and they have a particular passion for the flowers of cow parsley, hogweed, hemlock water-dropwort, wild angelica and other similar umbels. They are common on many garden flowers too. Surprisingly, they are less common in high summer.
Their markings can be quite variable with differing amounts of black and orange, the one in the photo veering more towards mostly black.