Hover flies are an extremely variable family of flies that range from the large, bulky and hairy to the small, slender, and shiny. There are more than 40 species in New Zealand. Common features of the family are large eyes (often wider than the front of the thorax) and a distinctive wing venation in which veins run parallel to the hind edge of the wing giving the appearance of a false margin. Although this venation is recognisable in pinned specimens, it will be very difficult or impossible to pick up while doing flower observations, so it is better to familiarise yourself with the appearance of some of the common hover flies beforehand. There are two basic forms of hover flies: the small-bodied types from which the common name is derived, and the large-bodied varieties that rarely hover.
The small bodied ones tend to be quite recognisable. These are the ones that have a distinctive hovering flight, in which they appear to hang still in the air (like a tiny hummingbird), and then dart off rapidly to a new location or settle on a flower. They often have banded abdomens and may have a black or metallic thorax.
The large-bodied varieties include some of the bee mimics like the drone fly (which are discussed separately above), and the narcissus bulb fly, which is a bumble bee mimic. Other large-bodied hover flies include the native Helophilus varieties which have a series of pale yellow and black stripes running lengthwise down the thorax and a variable number of yellow or orange patches on the sides of the abdomen. There is also a metallic blue variety that is likely to be confused with a blue-bottle blow fly. Don’t be too concerned if you can’t figure out the various large-bodied hover flies, as they will still be picked up in the basic “big flies” category and will hopefully be represented in your voucher collection.