Meet the bee-fly: the cute bee mimic with a dark side

Do bee-flies sting?

Despite their appearance, bee-flies do not bite or sting. They are mostly interested in finding nectar, mating and laying their eggs. 

How to see a bee-fly

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 17^oC. 

When they aren't whizzing from flower to flower, these sunseekers will often sunbathe on bare ground or dead leaves.

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.

The gruesome parasitic nature of a young bee-fly 

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.'

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.'

Power pollinators 

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.

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. 

Bee-flies to look out for in the UK

Dark-edged bee-fly (Bombylius major)

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

Dotted bee-fly (Bombylius discolor)

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

Western bee-fly (Bombylius canescens)

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

Heath bee-fly (Bombylius minor)

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-fly (Villa cingulata, V. modesta and V. venusta)

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.

Mottled bee-fly (Thyridanthrax fenestratus)

Where to see it: Heathland in Dorset, New Forest, Surrey, West Sussex and Berkshire (distribution map)

Flea bee-fly (Phthiria pulicaria)

When to see it: Late May to mid-August

Where to see it: Coastal dunes around the UK and sandy heaths in East Anglia

Black-winged bee-fly (Anthrax anthrax)

Where to see it: So far the black-winged bee-fly has been recorded in Cambridge and Canterbury

Take part in Bee-fly Watch

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.