A glance through social media in March and early April 2021 has revealed people’s sightings and photographs of some very charismatic and eye-catching insects, whose lifestyles are as fascinating as their appearance.
A winged wonder
You might see and hear the bee-fly in March/April or even as early as February in Cornwall, hovering by flowers on a sunny day – gingery-brown and furry (see https://www.cornwallwildlifetrust.org.uk/wildlife-explorer/invertebrates/flies/dark-edged-bee-fly).
They are probably most abundant in April/May, with some such as the scarce Western Bee-fly (Bombulius canescens) still around through the summer, so keep a look-out from now onwards, in the garden and on your wildlife walks.
Bee-flies seem adorable – quite like a bumblebee, with big, rounded eyes, a long proboscis for sipping nectar, and attractive pointed wings (just the two, as they’re a fly, not a bee). They won’t bite or sting, either. Wing patterns are a good way to tell the species apart, although they are a blur in flight, like the wings of hummingbird/bee hawkmoths). For ID, see: https://www.brc.ac.uk/soldierflies-and-allies/sites/www.brc.ac.uk.soldierflies-and-allies/files/Bombylius%20ID%20guide.pdf
Although they hover and skim like a helicopter and are as furry as a teddy bear’s paw, the incredible reproductive behaviour of the bee-fly is not endearing if you happen to be a solitary bee parent or larva. But please don’t hold this against the bee-fly, because nature is interdependent – part of a whole complex system – and the presence of bee-flies goes with the good news that we have a healthy solitary bee population.
Apparently, its bee-like appearance allows the female bee-fly to approach ground-nesting bee burrows. She hovers there before bobbing down to camouflage her eggs with dust and grit, then flicks the eggs into (or near) the open entrance holes! Having crawled deep inside the nest, a larva will gradually eat a host bee larva alive.
On the ground, underground and hitching an airlift
The other common sighting in early spring is the oil beetle, also dependent on solitary bees for its life cycle. In my area of East Cornwall, sightings usually seem to be of the Violet Oil Beetle, and I have found them in a range of habitats, usually somewhere where they are easily trodden on by people and dogs.
This wonderful animal, which appears black with a lovely violet sheen, and a hammered metallic appearance to the short wing cases if you look closely, trundles around country pathways, woodland and moorland (and my friend’s rural village garden). I have noticed them munching on blades of grass and celandines in particular, near the nests of mining bees. The mobile little head and unthreatening manner somehow gives them a rather comical appearance as they chomp and bumble obliviously on their way. They are slow enough to photograph with ease.
The corpulent female lays her eggs in a burrow she has dug in the earth. When the black, stick-insect-like larvae hatch out from the eggs, they become little hitch-hikers waiting around on shiny, star-like celandine flowers, and grabbing on to passing bees for a lift through the air. Yes, really.
If they pick the correct host, they end up inside the burrow, where they are able to eat its egg and pollen store. They shelter safely underground inside the bee nest over summer, autumn and winter, becoming a grub-like pupa that moults three times before emerging the following spring as the extraordinary-looking plant-eating adult, already on the lookout for a partner to begin the extraordinary life-cycle again.