In France there are around 530 different species of Hoverfly that are known to be present, albeit many are regional or localised and of course, unlikely as it may seem, there may be more yet to be discovered and classified. 

Hoverflies belong to the family Syrphidae, a family within the order Diptera (true flies). They are then divided into subfamilies and tribes but these divisions, although generally still used, are now considered to be artificial and subject to revision.

Most people will recognise some of the common ones from their gardens even though they may not know what they are. There will also be many people that may never have seen or noticed them, even more so for those that have lived in cities and spent their working life inside buildings. Often known as Flower flies in the USA and some other countries they have come to prominence as being important pollinators.

In some species, the larvae are saprotrophs, eating decaying plant and animal matter in the soil or in ponds and streams. In other species, the larvae are insectivores and prey on aphids, thrips, and other plant-sucking insects. Understanding these requirements will help us provide and conserve the conditions in which they can maintain healthy populations.   Some members of the Eristalini tribe are quite common and breed in decaying organic materials such as run-offs from dung heaps (Eristalis) or in ponds and ditches (e.g. Anasimyia). Some others, such as Myathropa and Mallota breed in wet rotting tree stumps and rot holes.   A characteristic feature of this tribe is the larvae known as "rat-tailed maggots" with a rear positioned telescopic breathing tube, allowing the larvae to breathe while living submerged in water or mud. Although many people are disgusted if they see these it’s important to conserve them and not think they are something horrible.

A few examples are provided here of common species that people are likely to see with a little information regarding their life cycle and behaviour.

So called rat-tailed maggots, (above), have a tube-like, telescoping breathing siphon located at their posterior end. This allows the larva to breathe air while submerged by making contact with the surface of the water. The siphon is usually about as long as the maggot's body but can be extended to several times the body length. This organ gives the larva its common name.

The most commonly encountered rat-tailed maggot is the larva of the drone fly, Eristalis tenax.. They live in stagnant, oxygen-deprived water, with a high organic content and  can live in sewage lagoons and cesspools. There are several of hoverfly species that share this manner of larval development. They do not live in clean water.  

Adults overwinter in sheltered places, sometimes in groups.

Above Syrphus ribesii which is a multiple brooded species that can usually be seen much of the year. It's a very common species throughout France with larvae that eat aphids. The photo shows a larva with aphid remains. 

The two varieties of the same hoverfly taken in our fields a few metres from each other at the same time, Volucella bombylans.   

Variety plumata with the pale tail and variety bombylans with the orange tail. These apparently mimic the Red tailed bumblebee and the Buff tailed bumblebee and lay their eggs in their nests as well as those of social wasps where the larvae eat the colony debris. The mimicry seems to be designed to fool predators and not the bees or wasps as both varieties use any nests.