An introduction to: hoverflies

What do you know about hoverflies? You only get one point for saying that they're flies and they hover!

They are one of those groups of insects that are found in almost every garden, they're often boldly coloured and day-flying, and many spend plenty of time in and around flowers. They are some of the friendly* faces you can get to know and understand and take notice of. (*'Friendly' as in they don't bite, they don't have any interest in coming into your house, and those whose larvae feed on aphids are the gardeners' friends.)

There are plenty of hoverflies still around in September, so I thought it was time to do a blog that will hopefully help you delve a little deeper into their world. All the photos below I took in my garden this week to give you a sense of what variety there is to be found.

So, let's start with the basics. Hoverflies are indeed a group of true flies, the Diptera, of which there are about 7000 species recorded in the UK. However, there are only about 280 species of hoverflies, very similar to the number of bee species here.

Of those 280, about 165 or so can be identified to species level by eye or with a handlens, according to Stuart Ball and Roger Morris whose WildGuides book, Britain's Hoverflies, I would heartily recommend.

Here's a typical hoverfly (below). It has the typical insect body structure of head, thorax and abdomen. The head has two very large compound eyes, and two knobby antennae sticking from between the eyes, which is an area called the frons and is yellow in this hoverfly.

The pattern on the back of the thorax and on the abdomen can be very useful for identifying many hoverflies, but be aware that in some species this pattern can be variable, and it can also vary between males and females.

I've also highlighted the scutellum, the fleshy section at the rear edge of the thorax - the colour and pattern of this can be useful, too.

But what makes this a hoverfly and not another type of fly? If we zoom in on the image above and look at the wing, we see all the veins that hold the wing rigid, and in hoverflies there is one line that cuts through the middle of the wing but then peters out. It is actually a fold rather than a true vein, and so is called the vena spuria - the spurious vein. Only hoverflies have this.

Also in hoverflies the veins don't extend out to the outer edge of the wing, creating what is called the false margin.

And I've also highlighted that this hoverfly has a prominent loop in the longest vein, which is a feature of the group of hoverflies whose larvae live in water and are called 'rat-tailed maggots'.

All this might seem a little technical, but because hoverflies often sit quite still in flowers, these are things you can see either in the field with the naked eye or if you take photos of them.

As well as looking on flowers, other key places to find hoverflies include basking on sunny tree trunks, on tree leaves where they might be supping honeydew exuded by aphids, and around ponds.

And when I say flowers, female hoverflies also need to suck up pollen to give them the nutrients they need to lay eggs, so you can find hoverflies on pollen-rich flowers such as plantains and even grasses. For them, lunchtime isn't all about drinking nectar!

So let's have a look at some hoverflies using some of the body parts we focused on above.

Here's a hoverfly (below) with a plain brown thorax and scutellum, two big orange triangles on the base of the abdomen, and you can see the loops in the wing vein. This is a very typical pattern for one of the drone-flies. There are a handful of species, and you can see drone-flies on the wing from March right through to the end of autumn.

Here is another hoverfly with orange triangles at the base of the abdomen, but an amber scutellum and a fluffy black tank-top! It also has a loop in the long wing vein, so it is another drone-fly, but one that mimics bumblebees. This is a hoverfly called Eristalis intricarius and this is a male; the female has a white 'tail'.

Sadly, not many hoverflies have English names in widespread use. I don't know about you, but I really struggle to lodge scientific names in my head. So I often have my own way of remembering hoverflies. Such as this one (below), which I call the 'Shoulder-stripe Hoverfly' but which is actually Xanthogramma pedissequum (can you see why I struggle with the names - that's way too many doulbe-letters!). But what a perfectly marked ickle beast.

One 'fact' many people quote about hoverflies is how their larvae feed on aphids, but we've already seen drone-flies whose larvae feed underwater on rotting plant material, and  Shoulder-stripe Hoverfly larvae are thought to live in ants' nests.

Here's another great pattern to spot (below), one of another group of hoverflies that are common in gardens and have earned themselves the nickname of the 'footballer hoverflies' - I think you can see why from the stripy shirt.

Talking of giving nicknames to hoverflies, let's return to the one at the very beginning. This, to me, is the 'Batman Hoverfly' - look at the rear black marking on the back of the thorax. No other hoverfly has this pattern. Its scientific name is Myathropa florea, and you can make out the loop in the wing vein so here is yet another hoverfly whose larvae live in wet places with decaying vegetation.

And let's finish with a really dramatic hoverfly:

This is a BIG hoverfly that mimics Hornets, which can make them look a little scary, but again they are harmless. This one, with its orange thorax and scutellum, is Volucella zonaria, and its larvae live in the nests of social wasps.

The Hornet Hoverfly is a bit of a southern speciality, but is expanding its way north. Just as with birds and butterflies and other wildlife, different species have different geographical ranges, but there are plenty of northern and upland specialities, so wherever you live there are interesting hoverflies to look for

So, when the sun next shines, get out and have a closer look. You too might find Batman, or the Footballer, or fluffy-jumper-wearing hoverflies to brighten up your day.