Prof Dave Goulson is one of the world’s foremost experts on insects. But there’s a special place in his heart for hoverflies, one of the prettiest flies around. Here he explains why we should nominate hoverflies as invertebrate of the year. They’re in the fly family – flies are insects with one pair of wings. There are lots of different species, some of them quite annoying, such as mosquitoes and houseflies. But the hoverfly is one of the prettier families of flies; they are colourful with yellow and black stripes to imitate bees and wasps. There are about 270 species of hoverfly in the UK of varying sizes, shapes and colours. They’re very easy to see in your garden if you go outside in the spring.
The adults visit flowers, which means that they’re quite important pollinators. Some flowers are better pollinated by hoverflies than they are by bees. Different flowers have evolved to attract different types of insects. Hoverflies really like small flowers laid out in clusters, and crops such as carrots are mainly pollinated by them. If we didn’t have hoverflies, we wouldn’t have as many strawberries, either, so good reason to be grateful to them.
The larvae of hoverflies are maggots. Some are predators and really important in crops, eating aphids in particular. I have them in my vegetable patch in the spring and summer nibbling away at the aphids, which is jolly kind of them!. Others are aquatic and help to break down organic matter that falls into little puddles and ponds. They have a long tail and hence are known as rat-tailed maggots, which doesn’t sound particularly appealing, but they’re quite sweet when you get used to them. They feed on organic matter and help to recycle nutrients back into something other organisms can consume.
Another purpose is that they’re food – a major source for lots of birds and some small mammals and reptiles. We know that hoverflies have declined: hoverfly ranges have contracted on average by 44% since 1980. It means each species has on average disappeared from nearly half of its range in 40-odd years. If this carries on, it means that many are going to disappear, which would be sad and have direct impact because of the roles they perform.
Some are migratory. There’s one called the marmalade hoverfly which migrates from Europe across the Channel at high altitude. Some years you get millions, and they’re very important in pest control because they’re predatory, so we should welcome them from the continent every year.
There are some really rare ones on the edge of extinction, such as the pine hoverfly which lives in Caledonian pine forests in Scotland. There’s only one tiny population left of them because most of their habitats have been lost. Some live in the nests of bees and wasps and hornets. There’s one that mimics bumblebees; it’s a beautiful insect, it’s big and furry, and it lays its eggs in the entrance to bumblebee nests. The maggots don’t do any harm; they’re kind of scavengers that live in the bottom of the nest and eat any detritus that the bees drop.
They are all very beautiful. But more than anything, they’re underappreciated. Bees tend to get all the credit in the insect world, and everyone likes butterflies because they’re pretty and easy to identify. But I think most people pay no attention to hoverflies at all, which is a real shame because when you start looking at them, they’re fascinating creatures and they do important stuff that is largely unrecognised. It’s about time they got some credit.
Invertebrate of the year 2025. The Guardian is asking readers to nominate species for the second annual invertebrate of the year competition. Read more about it and make your suggestions here or via the form below. Sign up to Down to Earth. The planet's most important stories. Get all the week's environment news - the good, the bad and the essential.
