[3][4] The species in genus Helophilus are large yellow-black hoverflies ranging in length from 9 to 16.5 mm.

Most of these flies have yellow stripes on their scutum, large yellow-orange markings on their abdomen, and an elongate pterostigma on the wing.

In Europe, flight periods commence as early as March and conclude as late as October.

[9] They make large amplitude dorsoventral movements of their abdomen while they are foraging on flowers.

[12] Migratory species may also be present in very high densities, which may make up for potentially lower pollinator efficiency.

The posterior end of the body is highly elongated into a telescopic siphon, which is extened to the surface and adjusted in length according to the depth of the water or mud.

[10] The larvae are similar to those of genus Eristalis, Eristalinus, Anasimyia, Lejops and Parhelophilus.

[17] When fully grown, the rat-tailed maggots leave the water and make a small oval chamber in damp earth nearby.

[10] Helophilus is mainly distributed in Europe, North America, Asia and New Zealand.

[19] The endemic New Zealand species are under the oldest genus-group name (Pilinascia), as a subgenus of Helophilus.

H. antipodus is a pollinator of the endemic orchid Dendrobium cunninghamii on the main island.