Bee-flies are back! | Citizen Science

Have you seen any bee-flies in your garden? Bee-flies look rather like bees but are actually true flies (Diptera). They have round, furry bodies and a long proboscis (tongue) held out straight. The proboscis can sometimes cause alarm but they do not bite or sting and just use it to drink nectar from spring flowers, often while hovering. Flowers with long nectar tubes such as primroses and lungworts are particular favourites, and bee-flies are likely to be important pollinators of these.

Bee-fly feeding from a primrose flower. Photo by Vlad Proklov, via Flickr, CC BY-NC 2.0

In 2019 bee-flies broke all previous records by first appearing on 17 February, about two weeks before their normal emergence date. This year they were spotted on a more usual 6 March and will continue to fly for the next month or two.

Join in with Bee-fly Watch this year to help track their emergence across the UK. Look out for bee-flies on sunny days, particularly around flowers and submit your records here. You can also share your photographs on social media using #beeflywatch.

The bee-fly life cycle

Adult bee-flies only drink nectar, but their larvae have a rather different lifestyle preying on solitary bee larvae.

An adult female bee-fly collects dust or sand at the tip of their abdomen and use it to coat their eggs, this is thought to provide camouflage and add weight. Next, she flicks her eggs in the direction of solitary bee burrows, the eggs hatch and the bee-fly larva crawls into the burrow and feeds on the pollen stores and bee larvae.

Once fully grown the bee-fly larva pupates and waits till the spring to emerge as an adult and start the cycle again. Although this may sound bad for the solitary bees, bee-flies are a natural part of UK ecosystems and there is no evidence they harm bee populations.

Bee-fly species

There are four species of Bombylius in the UK, and the one you are most likely to see is the Dark-edged Bee-fly (Bombylius major). This fly is around 1 cm in length and its wings have a dark brown edge. It’s an excellent flyer, not only hovering in front of flowers but able to rotate (yaw) its body in flight.

Dark-edged Bee-fly (Bombylius major). Photo by Richard Bartz, via Wikimedia Commons, CC BY-SA 2.5

There are three rarer bee-fly species in the UK. As its name suggests the Dotted Bee-fly (Bombylius discolor) has spots on its wings and also a darker body colour. This species is only found in the south of England but does sometimes occur in gardens. There are also two smaller species which tend to fly later in the year and are rarely seen in gardens: the Western Bee-fly (Bombylius canescens) and the Heath Bee-fly (Bombylius minor).

Unsure which bee-fly you have seen? Check the identification guide here: or email a photograph to the Natural History Museum Identification Service. And don’t forget to let Bee-fly Watch know which you find!

Dotted Bee-fly (Bombylius discolor). Photo by ©entomart, via Wikimedia Commons.





One Reply to “Bee-flies are back! | Citizen Science”

  1. Interesting. I didn’t know bee-flies were parasitical on bee larva. They are certainly distinctive-looking insects. I see them fairly often in Southern California.

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