Is it a Hoverfly?

Hoverflies are probably most often thought of as those black and yellow mimics of bees and wasps in the subfamily Syrphinae but there’s really a lot of diversity in the family on top of these so a few extra pointers may be of use.
 
1) Hoverflies are flies!
That means they have two wings, not four like bees and wasps. Also, most hoverflies lack the narrow ‘wasp-waist’ characteristic of most bees and wasps (although there are a few that mimic the waist a bit). The wing venation is also quite simple compared to bees and wasps. The next pictures illustrate this and also some of the other points that will be raised below.

A hoverfly	A bee (Megachile)

 
2) Hoverflies are Brachyceran (‘Short-horned’) flies.
That means that they have short antennae with only three segments, unlike ‘Nematoceran flies’ and bees/ wasps, which have long antennae with many segments. (See above - and don't be confused by the long bristle attached to the antennae) A few hoverflies, like the one below do mimic the long antennae of bees/wasps, but if you look closely they still only have three segments - just three elongated segments!

 
3) Hoverflies are Aschizan flies.
That means their face doesn’t look like the Sarcophaga below - with white tracks next to the eyes and a big cavern in the middle of the face below the antennae. Most other Aschizan families are rather small creatures.

A hoverfly	Not a hoverfly (Sarcophaga)

 
4) Hoverflies are not bristly.
A few species (notably Volucella sp) have some discreet bristles - but if your fly looks like a punk rocker, it’s not a hover!

Not a hoverfly! (Tachinidae)

 
5) Hoverflies have big eyes!
They cover most of the sides of the head - and in males they usually meet in the middle of the top part of the head. They are not as comically big as in the family Pupunculidae however! (That’s another Aschizan family - probably the most similar to hoverflies)

6) Wing venation.
Hoverfly wings have:
 a) a ‘vena spuria’ (spurious vein). This is not a true vein - it is not connected at either end (so it is also sometimes called the ‘floating vein’). It is actually a toughened fold in the wing. Only hoverflies have this, and only one British hoverfly does not have it (Psilota anthracina)
 b) a ‘false margin’. Cells ‘dm’ and ‘r4+5’ are well separated from the back edge of the wing by a vein.
 c) a long pointed anal cell that doesn’t quite reach the back edge of the wing.

HOVERFLIES
Eupeodes	Eristalis
Eumerus	Microdon
NOT HOVERFLIES!
Pipunculus (Pipunculidae)	Eriothrix (Tachinidae)

Posted on June 28, 2023 01:52 PM by matthewvosper