Charlotte Owen of the Sussex Wildlife Trust decribes an unusual Spring visitor.
As spring gets under way and flowers begin to bloom, we'll start to see more insects on the wing. Alongside the familiar buzzing of the bumblebees, busily foraging for nectar and pollen, keep an eye out for something a little bit different. It certainly looks like a bee, and it even buzzes like a bee, but its legs are a bit too gangly and there is a long, pointy bit at the front. Is it a bee? Is it a fly? Well, it's a bee-fly.
This fascinating insect is somewhat unimaginatively named for its half-bee, half-fly appearance. It is in fact wholly fly but it has evolved a cunning disguise so that it can masquerade as a fluffy bumblebee. There are four species of bee-fly in Britain but the one most commonly seen is the dark-edged bee-fly, which has a dark-coloured band along the front edge of each wing - but this can be hard to see unless the bee-fly settles. They often visit gardens and parks, especially in spring. The long 'nose' is actually a tongue, or proboscis, used to sip nectar from its favourite flowers: primrose, ground ivy, blackthorn and wild cherry.
Bee-flies don't sting or bite and are completely harmless to humans but they do have a dark side. They are parasites and lay their eggs in the nests of solitary mining bees, the ones that dig tiny burrows in the ground. Thanks to their cunning camouflage, female bee-flies can accomplish this dastardly deed without drawing unwanted attention. Their larvae will then hatch out and lurk in the shadows of the burrow until the unsuspecting mining bee larvae are big and juicy enough to make a decent meal.
If you spot a bee-fly on the ground it's likely to be a female getting ready to lay an egg, and it's a fascinating process. She will first dip the tip of her abdomen into the soil to coat the tiny egg with soil particles, which provides effective camouflage but also adds some strategic weight. This is key to delivery: she will hover over a mining bee's burrow and flick the egg towards the entrance, like throwing a dart,and the added weight makes it a lot easier for her to score a bullseye.
