It might seem strange to you, but for me, finding and photographing hoverflies in my garden was a fascinating little hobby, and it led me to develop a deep interest in flies. I already had a general interest in nature, and a particular interest in insects, but once I started really looking at hoverflies and trying to identify them so that I could label my photos correctly, I was hooked.
If you take the trouble to look, you’ll see quite a few flies visiting flowers. If you look more closely, you’ll find that many of the ‘bees’ that you are seeing are not bees at all, but merely flies which look like bees. These flies are usually hoverflies and totally harmless. How do you tell the difference? Well, the easiest way to tell a bee from a fly is the shape of their heads and eyes and the fact that flies (usually) have little short stubby antennae instead of the long, waving antennae of the bees.
I’m sure you’ve all seen the the striped hoverflies which sit and look pretty on the more open garden flowers, or hover like little mini helicopters above and around their food source. But hoverflies are not all stripey – some are black, some are brown, some are patterned and some are not – and their size ranges from a few millimetres to twenty or more. They are common flower visitors, but that’s not the only place you’ll find them. For instance, members of the Helophilus genus of the family Syrphidae2 do visit flowers, but they also hang around water margins, so you’ll often see them around garden ponds, especially if there is some nice wet mud around the edge. These fairly large flies are banded and patterned with various shades of orange, yellow, and brown so dark that it’s almost black, and they look as if they’re wearing little football jerseys! I spent quite a while this summer sitting by my newly dug turf-edged pond, watching three female Helophilus pendulus stake out their territory, indulging in what looked like aerial battles to mark out their air-space and chasing other females away from a particularly well-sited pond plant.
They were joined one day by an Eristalis pertinax female (one of the bee-mimic hoverflies) also looking for some very wet mud, because both Helophilus and Eristalis species lay their eggs in or near water. The larvae eat their way through the organic debris they find there, staying completely submerged and getting their air by means of a long telescopic breathing tube which extends from their rear. The breathing tubes end in an arrangement of fine hooks which cling onto the surface tension of the mud or water to keep the airway open while the larvae – known as rat-tailed maggots – munch away below the surface. Some genera of hoverfly have larvae (without rat-tails) that live in ants’ nests, wasps’ nests or bees’ nests. Others live on stems and leaves, under bark, in rotting compost, in drifts of dead, wet leaves, in sap runs, in hollow thistle stems, in rotting wood or in water-filled rot-holes. This is one very good reason why you should try not to be too tidy a gardener – you could be ‘tidying away’ next summer’s crop of hoverflies!
Many hoverflies are so small that you probably don’t notice them at all. The tribe Bacchini, for instance, includes many species which – to the naked eye – all look small and black as they fly silently around your lobelia, forget-me-nots and dandelions. Known to the dipterist as LBJs3, they are the curse of the amateur because they are so difficult to identify without microscopic examination. In the case of one Platycheirus species, it comes down to the shape and length of one bristle on the foreleg of the male, and in another, whether a small depression on a front leg has a ‘lightning’ shaped mark in it or not. For other Bacchines you might have to examine the genitalia – and no, I have not so far done this.
There are wasp mimic hoverflies and bee mimic hoverflies and some which look like other types of fly. Some are shiney and some are dull, some are metallic while others are furry. Hoverflies are interesting and very, very varied, and there are hundreds of different species of them in the UK and I can’t possible mention them all. You see, though I do love them (and I’m learning) I am no kind of an expert.
However, I can’t leave you without mentioning the big hornet mimics. Volucella inanis and Volucella zonaria really are often mistaken for hornets but they are just flies, have no sting and cannot bite. They are beautiful velvety yellow, brown/black/red beauties which are incredibly photogenic. Originally considered a migrant species, there are now areas in the south of the UK where they do breed, though they sometimes don’t survive our winters. These Volucella species have now been found as far north as Cumbria, and are among those hoverflies which mimic bees or wasps for self-protection, because they use their camouflage to enter wasps’ nests to lay their eggs.
To sum up, hoverflies are very beneficial insects and we need to encourage them.
Why? Because although there are some which will damage our plants (the Narcissus Fly, Meredon equestris, for example), most are pretty good at helping farmers and gardeners. They deal with rotting material for us, they eat a huge amount of insect pests, and what’s more, they are seriously good at pollinating crops and flowers.
Some pollinate various wild flowers which bees simply don’t visit, and there are some plants which have evolved to attract hoverflies for pollination – the orchid species Epipactis veratrifolia, produces a pheromone which is indistinguishable from the alarm pheromone of aphids, which attracts hoverflies, and the plant gets itself pollinated!
If you want to help hoverflies, you can do one or more of the following: make a garden pond and a compost heap, leave some long grass and other undisturbed areas, leave some dead leaves lying on the ground over winter, allow some rot-holes and a bit of dead wood to remain on your trees, and plant plenty of pollen- and nectar-rich flowers, trees and/or shrubs. If you feel particularly enthusiastic, you could join the Buzz Club’s Hoverfly Lagoon Project.
Oh yes. And whatever else you do, DON’T use insecticides in your garden!
1 – A dipterist is someone who studies flies, because the order of insects we study is called Diptera.
2 – Syrphidae is the diptera family which covers hoverflies.
3 – LBJ = Little Black Job
Interesting information. Thanks for the education.