Bee-flies: fluffy, cute – and clever!
The first bee-fly of the year has been reported, so we asked Martin Harvey of the Bee-fly Watch project to reveal the extraordinary secrets of this tiny herald of spring
On a sunny day, any time from late February to early June, find your nearest patch of flowers and look for a small ball of fluff hovering above them. Does it have an implausibly long and straight proboscis (feeding tube) extending forwards from the head? Does it have long spindly legs? If so you have probably seen a bee-fly. Get a photo if you can, and you can then take part in the annual Bee-fly Watch to help us find out more about these brilliant beasties.
Bombylius major, the Dark-edged Bee-fly: that long proboscis is for drinking nectar, not stinging!
Bee-flies are true flies, but they look a bit like small bumblebees. There are four species of bee-fly in the genus called Bombylius, of which two fly in early spring and two in summer. The one that you are most likely to see is the Dark-edged Bee-fly (Bombylius major, above) which is found pretty much everywhere in Britain except on high moors and mountains, and has a dark marking running along the leading edge of its wings. If you are in southern parts of England or Wales you can also look out for the Dotted Bee-fly (Bombylius discolor), which gets its name from the blackish spots on its wings.
Fluffy and cute they may be, but why deadly? This is down to the life-cycle of the bee-fly. Females have the amazing ability to ‘flick’ eggs out of their abdomens, and their targets are holes in the ground. But not just any hole: what they are trying to find is the entrance to a solitary bee burrow. If they can get their eggs to land in or near a bee burrow, the larvae that hatch out of the eggs will find their way into the burrow, where they will feed on the bee’s larva. The following spring a lovely fresh bee-fly will emerge into the open, rather than a lovely fresh bee.
But before producing and flicking her eggs the female bee-fly will land on some sandy soil and wriggle her back end through the sand, picking up grains into a special chamber at the tip of her abdomen. Each egg she produces is slightly sticky, and picks up a fine coating of the sand grains. This helps prevent the egg drying out before the larva has had a chance to hatch.
No long-term harm is caused to the bee populations – bee-flies and bees have evolved alongside each other for millennia, and if you are seeing bee-flies that is a good sign that there is a healthy abundance of bees in your area. And while bee-flies may not be best friends with bees, they do act as pollinators themselves!
The organisation for people with an interest in flies is called the Dipterists Forum (‘Diptera’ being the name for the order of insects that are the true flies). Each year, Dipterists Forum runs a Bee-fly Watch project to track what is happening with these fascinating flies. If you see a bee-fly, try to get a photo and then you can add your record and contribute to Bee-fly Watch. Full details, including a downloadable identification guide and an online recording form, can be found here.
Your records of bee-flies will be gratefully received, but recording them is not compulsory, and if you’d rather just go out in the spring sunshine to enjoy watching bee-flies as they go about their business that’s fine, too!
Further information:
• Take a photo and report your bee-fly sightings here: dipterists.org.uk/bee-fly-watch
• Read this bee-fly blog post by Erica McAlister of the Natural History Museum: www.nhm.ac.uk/discover/bee-flies-cute-bee-mimic-with-a-dark-side.html
• Listen to Erica on the UK Wildlife podcast: www.uk-wildlife.co.uk/ep44-bee-flies-with-dr-erica-mcalister/
• Find other bee-fly enthusiasts by searching for #BeeFlyWatch on social media
