I was once asked by a visitor if I could tell her what an insect she had just seen was called. She said that the best description she could give was that it looked like a flying shrew! I thought this was a great description of the very distinctive, fluffy little insect called a bee-fly. Bee-flies are bee mimics, looking a bit like a smaller bumblebee.
Early in spring, as soon as the bright spring flowers begin to appear, bee-flies make their appearance. The Dark-edged Bee-fly Bombylius major is the most common of the species found in the British Isles. It is a member of the Diptera (true flies), and has six long, thin legs, a very long rigid proboscis (long tubular tongue) and a plump, rounded furry body covered with tawny orange/brown hair. The Bee-fly Bombylius major is 10 to 12mm long, excluding the proboscis which adds another 6mm. The proboscis is held out in front of the fly, even when it is resting. Bee-flies have two wings (bees have four) heavily marked with darker colours, although this is difficult to see when they are hovering.
Bee-flies are quite mobile, found in grassy sunny places, including gardens, from March to June. They dart from flower to flower, poking their proboscis into flowers to sip nectar. Although appearing to hover while feeding, they usually cling to flowers with their spindly legs. They fly low, hovering with a high-pitched whine over spring flowers such as speedwell, ground ivy, violets, primroses and cowslips as well as many more. On Magog Down they can also be seen feeding on the blossom of the low hanging branches of hawthorn trees in the hedges and on the sunny edges of North Down. They also sunbathe on bare ground and dead leaves. Approach with care, if you make a sudden movement or your shadow falls on them they will be gone.
Bee-flies have an interesting, parasitic life cycle. Females fly over the nest holes of various species of solitary bees and wasps, laying (i.e. flicking out) their eggs in the hope that they will land in or near a solitary bee’s nest. On hatching, the larva wriggles its way into one of these holes. At first it feeds on the pollen and honey stored by the solitary bee for its own larva. After its first moult the bee-fly grub changes into a carnivore, feeding then on the host larva. Bee-fly pupae have been found in nests of solitary bees, so it seems that the bee-fly grows to maturity within the host’s home, only emerging as an adult in spring. The sudden change in diet by the larva is unusual among insects, especially since the bee-fly returns to a diet of nectar as an adult.
Photos by Nick Beale