Hoverflies

by Dave Emley 

You've all seen them; your remaining Autumn flowers may be covered in them, but would you recognise them for what they are?

The Gardener's Friend

Hoverflies are a group of about 250 species of fly, that mimic or resemble various species of bee and wasp. They are quite harmless, but, by copying something that is harmful, they gain protection – it is called Batesian Mimicry.

Hoverflies are often mistaken for wasps, but while wasps have two pairs of wings, all flies have only one pair. Wasps also have long antennae of 12/13 segments, while hoverflies have small antennae of 3 segments. There are other characteristics, hovering for one, but after a while they take on a distinctive "jizz". Also, in males the eyes touch while they are separated in females.

There are several thousand types of bee and wasp and so there are many different sizes, shapes and colours of hoverfly. As their name suggest, many are superb hoverers.

Hoverflies are not too difficult to identify, there are readily available guides to them and you can always upload a photo to the Aston Lodge Residents Facebook Group for me to identify! The number of species you could find in your garden might surprise you. For instance, in Leacroft, we have recorded over 50 species.

While quite a few hoverflies are dark and small, some are very colourful and quite large, and these are the ones which I just want to introduce you to below.

Hoverflies can be divided into a number of groups, depending on how the larvae live. The largest group are the aphid feeders, followed by those that live in a liquid environment, like sewage, cow dung and water. These have a long breathing tube at the end of their abdomen, that reaches the liquid surface, while they feed on various organic matter below. They are quite often called rat-tailed maggots. We then have a small group that feed as scavengers, in the nests of bees and wasps, another group lives in rot-holes in tree trunks and another group feeds on sap runs from tree trunks.

For gardeners it is the aphid-feeders that are of most interest, but they are also great pollinators too. It's not all good news though and it has to be said that there are a few that attack bulbs and thistle stems, for instance.

Hoverfly Species

Below is a selection of the more distinctive species, showing the range of colours, shapes and sizes. I’m sorry but most do not have English names!

Eristalis

These are large flies with the two below being very common, and on the wing right through to early winter. They look very similar, but E. tenax has black front feet while E. pertinax has yellow ones, it also has a more pointed abdomen. There are other species in the genus. The larvae are of the rat-tailed type.

Syrphus

There are several similar species in this genus, all having yellow bands on the abdomen. The one below is the commonest. The larvae are aphid feeders.

Episyrphus

There is only one species in this genus Episyrphus balteatus aka Marmalade Fly. It may surprise you to know that it is a migrant, with large numbers some years entering the country. It is another aphid feeder.

Helophilus

A distinctive genus of 3 similar species, of which this is the commonest. The larvae are of the rat-tailed type, found in decaying vegetation at the edge of ditches and ponds.

Myathropa

Only one species in the genus. It is often called the Batman fly, because of the pattern on its thorax resembling the Batman logo! It is another rat-tailed maggot type.

Sericomyia

Just three species in the genus, two are wasp imitators the other, S. superbiens, a bumblebee mimic. S. silentis is one of our largest hoverflies and a rapid flyer. The larvae are rat-tailed maggot types, living in peaty pools and ditches.

Leucozona

Species in this genus differ markedly from other hoverflies. There are just three species, two of them shown below. The larvae are aphid feeders, while the adults are often seen on umbel flowers like Hogweed and Angelica.

Volucella

Large and distinctive hoverflies whose larvae scavenge in the nests of bees and wasps. There are 5 species of which this is the most distinctive.

Xylota

A distinctive group of rather elongate hoverflies that generally mimic sawflies rather than bees and wasps. Often seen running over vegetation, feeding on honeydew and pollen, rather than visiting flowers. There are 7 species usually associated with decaying timber.

Rhingia

There are two very similar and distinctive species. The long snout is unique and allows the insect to reach deeper flowers, hence its common name of Heinekin Fly, because it reaches the parts other hoverflies cannot reach! The larvae live in cow dung.

Merodon

Just the one species of this variable bee mimic. Its larvae feed on the bulbs of Daffodil, hence its common name of Narcissus Bulb Fly

Xanthogramma

A distinctive group of 3 species. The one below being the commonest. The larvae live in the nests of ants where they have a scavenging role.

Syritta

A species whose larvae feeds in rotting vegetation like compost heaps, while the adults visit flowers. It is one of our commonest species and is also a migrant.

Baccha

A very small and slender hoverfly with a wasp-like waist. Found in dappled shade where it hovers amongst leaves. The larvae feed on aphids.

Eupeodes

A group of 9 species, of which this is the commonest. They all have a pattern of crescent-shaped or lunulate spots. The larvae are aphid feeders.

Chrysotoxum

Large and very smart wasp mimics, with long antennae compared with other hoverflies - but still only 3 segments. The larvae feed on root aphids in the nests of ants. The one illustrated is the commonest of 7 similar species in UK.