Is it even April until you’ve seen your first dark-edged bee-fly? For me: no, it is not. I’m obsessed with them.
I stalk primroses, ground ivy, lesser celandine and cowslips in the hope of seeing one. I stand beneath cherry blossom and try to make out their high-pitched buzz among other pollinators with deeper drones.
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Bee-flies creep up on you somehow – a shadow, a hint, a darting movement in the corner of your eye. Then, suddenly, there it is, hovering between flowers with its huge, outstretched proboscis. The ribbon on April is cut.
Bee-flies are so-named because they are, literally, flies that look like bees. There are four species in the genus Bombylius, of which the dark-edged bee-fly (Bombylius major) is the most common.
It’s found in gardens and allotments as well as wilder habitats, and is distributed across the British Isles.
It has a ginger abdomen up to 1.8mm long, dangly legs and a proboscis that measures up to 7.5mm – nearly three times its body length.
In the south of England up to the Midlands, and in south Wales, you may also see the dotted bee-fly (Bombylius discolor), which has beautiful dotted wings and a darker abdomen, on which the female has a line of white dots.
It also frequents gardens, along with wilder habitats. The other two species, the western bee-fly and heath bee-fly, are smaller and have more specialist habitat requirements, so are less common.
All four species have a long proboscis (tongue), which extends forward from the head and enables them to drink nectar from flowers with long nectaries, such as primroses. But this tongue also makes them look like flying, fluffy narwhals – there’s nothing else quite like them.
Last year seemed to be a good year for the dark-edged bee-fly, and I was lucky to see two mating in mid-April. They rested for ages on the ground, bum to bum, then flew upwards, still connected and with much buzzing, before separating.
One of them (I assume the female) then sat on a post and indulged in a post-coital wash, before presumably heading off to lay her eggs.
Many years ago I also watched a bee-fly laying eggs, without knowing what I was looking at, sadly.
All four of our Bombylius species are parasitoids of ground-nesting solitary bees, and the females hover over the bees’ nest tunnels, flicking their eggs in with varying levels of precision.
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Before laying eggs the female rests on sandy ground and absorbs grains of soil, sand or grit into her cloaca, which she uses to coat the eggs.
This camouflages them somewhat and perhaps makes them less detectable in the nests of their host bees, but also makes the eggs heavier and therefore easier to aim. Aren’t bee-flies clever?
Once hatched, the larvae eat the bee grubs, then overwinter in the nest and emerge a year later as adult flies, along with the bees that weren’t eaten.
The dark-edged bee-fly parasitises the nests of solitary bees in the Andrena genus, including Clark’s mining bee and the tawny mining bee. Both are common and nest in large aggregations, so are easy to spot.
Other species that nest in smaller, scattered aggregations, such as the chocolate mining bee, are also used.
If you want to spot a dark-edged bee-fly this month, keep your eyes peeled for gentle hovering over low-growing spring flowers. You might also stalk large aggregations of solitary mining bees in the hope of seeing the great egg-flick.
But be quick, April really is the only month to see them – that’s why it doesn’t start until you have.
Top image: bee fly on a salvia flower. Credit: Ozgur Kerem Bulur/Science Photo Library/Getty Images
