A dotted bee-fly (Bombylius discolor) © Anna Seropiani/ Shutterstock.com
Bee-flies look adorable. Seeing the dark-edged bee-fly hover in mid-air, some people describe it as a tiny, fluffy, flying narwhale. It has a hairy little body and face, and a very long, straw-like tongue.
At a glance, it's easy to mistake one for a bee. But these small fluffy creatures buzzing around looking for nectar are actually flies. And they have a fascinating lifestyle.
The long, tongue-like mouthpart of Bombylius bee-flies is sometimes mistaken for a stinger or causes concern due to its mosquito-like appearance. But bee-flies neither bite nor sting. © Stefan Rotter/ Shutterstock.com
Despite their appearance, bee-flies do not bite or sting. They are mostly interested in finding nectar, mating and laying their eggs.
If you see something that looks a little like a bee, check out its wings. A bee has two pairs of wings and rests with them close to its body, while a bee-fly has one pair and rests them away from the body.
Bee-flies have short antennae. Their hovering style of flight is also quite distinctive, although hairy-footed flower bees (Anthophora plumipes) hover well too - but these have much longer antennae and thicker, hairier legs.
If you head outside on a warm spring day, you might be lucky enough to spot a dark-edged bee-fly (Bombylius major). Its high-pitched hum may catch your attention before you see it.
This is the most common bee-fly species in the UK. It is widespread across England, Wales and Scotland, occurring in urban gardens and city parks as well as in woodland and coastal areas.
It is one of the earliest bee-flies to emerge. Having pupated over winter, dark-edged bee-flies usually start to appear in March, but people sometimes report sightings as early as mid-February after unseasonally warm and sunny days - they don't usually fly in temperatures less than 17oC.
When they aren't whizzing from flower to flower, these sunseekers will often sunbathe on bare ground or dead leaves.
The dark-edged bee-fly (Bombylius major) is the UK's most common bee-fly species © Russia piton/ Shutterstock.com
Resting with its wings pointing upwards, the dark-edged bee-fly looks like a little stealth bomber. It has a dark, uneven band along the front of the wings.
Depending on where you live, you might also see a dotted bee-fly (Bombylius discolor) in spring. Currently found mainly along the south Wales coast and in southern England as far as the Midlands, this species is spreading north. You will have to wait until this bee-fly is resting to see the lovely little dots on its wings.
Two more UK species (also in the genus Bombylius) share the same fat and fluffy resemblance to bumblebees, and the long mouthpart. But these are much rarer.
In total, 10 bee-fly species live in the UK. Find out more about them at the end of this article.
Two dotted bee-flies (Bombylius discolor) covered in dew, resting on a flower bud © Marek R Swadzba/ Shutterstock.com
While adult bee-flies are adorable, a young bee-fly isn't quite as endearing. The larva is a parasitoid, meaning it is a parasite that will end up killing its host.
Many bee-fly species are parasites of bees and wasps, but there are some that target beetles, grasshoppers, ants, moths or caterpillars.
Dr Erica McAlister, Senior Curator of Diptera at the Museum, explains how a dark-edged bee-fly lays her eggs in a solitary bee's nest and the unfortunate fate of the bee larvae when her eggs hatch:
'First the female moves her abdomen in a twerking motion to scoop up sand and gravel to coat the eggs. The sand protects and camouflages the eggs while also giving them extra weight.
'She then flies over to the solitary bee's nest and flicks out the eggs, hoping they will hatch near or in the nest.'
The dark-edged bee-fly's ovipositor (egg-laying tube) has a spine that allows her to flick her eggs, adds Erica.
'This helps her do something called bombing, where she fires off a row of eggs. She is essentially carpet-bombing her eggs, which she has to do while the bee is away from its nest.'
A female dotted bee-fly flicks her eggs while hovering near the nest entrance of a host mining bee. All Bombylius species are able to flick their eggs like this. © Nick Upton/ Alamy Stock Photo
The bee-fly needs to lay her eggs quickly as she is competing with other flies and wasps that are also trying to parasite the solitary bees. 'It's carnage and mayhem in your garden,' says Erica.
When the eggs hatch, the bee-fly larvae are very active. They have false legs that they use to enter the burrow of the bees and they have been known to stuff their faces with all the pollen left for the bee babies. Then they go through a second metamorphosis, called hyper-metamorphosis, which is very rare in the insect world. 'It's like going from an active toddler to an enormous, sedentary teenage larva that eats the bee grubs,' says Erica.
Parasitism is very common in the animal world. Scientists estimate that around 40% of all described insect species are parasites, and this is probably a low estimate as we haven't counted them all.
Bee-flies do not have a negative impact on solitary bee populations or their other hosts and parasitism is all part of a healthy ecosystem. Erica adds, 'You can have a wasp that is a parasite of a spider and then a bee-fly that is a parasite of the wasp, so it's a parasite of a parasite, which is quite fun and interesting.'
Like bees, adult bee-flies are great pollinators.
The dark-edged bee-fly's long, straw-like tongue (called a proboscis) is the perfect length to reach the base of certain flowers, such as primroses. It can also extend its mouthparts to reach into flowers.
A dark-edged bee-fly about to drink from a primrose. Its tongue will reach deep into the throat of the flower to access the nectar. © Bill Coster/ Alamy Stock Photo
Erica says the bee-fly holds itself to the flower with its front legs and then feeds while buzzing mid-air.
'Bee-flies can hover mid-air very efficiently,' she adds.
While feeding, the bee-fly's tongue gets covered in pollen, which it takes to the next flower in its search for nectar.
Not all bee-flies insert their proboscis into the flower, some stab the bottom of the flower as a quick and dirty shortcut to get the nectar. This sometimes earns them the name 'flower thieves' because they don't pollinate the flower when they do this. Some bees show the same nectar-robbing behaviour.
Like us, bee-flies have favourite colours. They like to feed from flowers that are purple, violet, blue or white and aren't attracted to bright yellow or pink flowers quite as much.
A dark-edged bee-fly searches for nectar. White flowers are a bee-fly favourite. © Keith Hider/ Shutterstock.com
The dark-edged bee-fly is also called the greater bee-fly and large bee-fly although its body is only just over a centimetre long © Richard Bartz (CC BY-SA 2.5) via Wikimedia Commons
When to see it: March (occasionally mid-February) to late June
Where to see it: England, Wales and Scotland (distribution map) in a wide variety of habitats including parks and gardens
This species has gorgeous, dotted wings. The female also sports a line of white dots on its rear. © tasnenad/ Shutterstock.com
When to see it: Late March to mid-June
Where to see it: Southern England and along the southern coast of Wales (distribution map) in a variety of habitats including parks, gardens and allotments
The western bee-fly has unmarked wings © cilko1/ Shutterstock.com
When to see it: Early May to mid-August
Where to see it: Southwest England and southern Wales (distribution map) in flowery grassland habitats, including hillsides and riverbanks
The heath bee-fly has been recorded in a variety of distant locations including the Isle of Man, west Wales and the Isle of Wight. But it now appears to be mostly restricted to Dorset, where it lives on heathland vulnerable to urbanisation. © Stephan Czuratis/ Shutterstock.com
When to see it: Early July to late August
Where to see it: Heathland and sandy banks in east Dorset and the Isle of Man
Villa bee-flies are less rotund than Bombylius species, with blunter ends to their abdomens and short mouthparts. Of the three UK species, the dune villa (Villa modesta, pictured) is the one seen most often, while the heath villa (Villa venusta) hasn't been recorded here since 1958. © S Rae CC BY 2.0) via Flickr
When to see them: June to September
Where to see them: V. cingulata: southern England, generally in areas with short turf or little vegetation cover. V. modesta: coastal dunes. V. venusta: heathland in Surrey, Dorset and Devon.
The mottled bee-fly has a short tongue, distinctive mottled wings and a patterned body. It can often be spotted hovering over sandy patches between heather or basking on sandy footpaths. © Dom Greves/ Alamy Stock Photo
Where to see it: Heathland in Dorset, New Forest, Surrey, West Sussex and Berkshire (distribution map)
When to see it: Late May to mid-August
Where to see it: Coastal dunes around the UK and sandy heaths in East Anglia
Anthrax is Latin for coal and this bee-fly is very black, very distinctive and doesn't mimic a bee in looks. It's a recent arrival into the UK and was spotted by an amateur entomologist in a garden in Cambridge. © Frank Vassen (CC BY 2.0)
Where to see it: So far the black-winged bee-fly has been recorded in Cambridge and Canterbury
If you see a bee-fly, you can record your sighting on the Bee-fly Watch website.
Your record will help scientists learn how the distributions and flight seasons of bee-flies in the UK are changing.
To help determine emergence times for the sexes you can also record whether you have seen a male or female bee-fly. The males have large eyes that touch on top of the head. The eyes of a female bee-fly are smaller and not joined together.
Follow Dr Erica McAlister on Twitter @flygirlNHM
Find out about the plants and animals that make the UK home.
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