Helophilus pendulus is a European hoverfly. Its scientific name means "dangling marsh-lover" (from Greek helo-, "marsh", -phil, "love", Latin pend-, "hang"). It is a very common species in Britain, where it is the commonest Helophilus species. It is found throughout Europe from the Mediterranean to Scandinavia, westward to the Faroe Islands and Iceland, and through eastward through Russia from the Kola Peninsula south to Crimea and across Siberia to the Pacific Ocean.
It also has the common name sun fly, although this is probably based on a mis-reading of helo- as helio-.
It is associated with a wide variety of waterbodies, from large lakes and rivers down to areas as small as ditches, small ponds and muddy puddles. Larvae have been found in cow-dung, very wet manure or very wet old sawdust.
This species visits flowers; it also commonly rests on leaves. It often emits a buzzing sound when resting. It is a notable wanderer and can be found well away from water. The larvae feed on detritus.