Species of the Month - May 2017

Dark-edged Bee-fly

Bombylius major

This is the only Bee-fly species hardy enough to live in our part of the country, so we simply call it the Bee-fly, but it is actually one of nine British species.  It can be told from the others by the wing pattern, with a sharp division between the dark leading half and the clear trailing half, hence its full name is the Dark-edged Bee-fly.

This wing pattern is hard to see, as an active Bee-fly keeps its wings whirring all the time, whether hovering beside a flower to extract nectar or standing on the petals for a better grip.  But it can be safely identified from its size (8-10 mm long), behaviour, extremely long proboscis, and bumblebee-like appearance.

It takes great patience to get a photo as good as that by Caroline Anderson above, showing the wing markings clearly while the insect is at rest.

This is a more typical view, with whirring wings, and proboscis like an extra leg.  The photo was taken on 25 March, our earliest Bee-fly on record.  Most of our records are in May with a few in April.
 

This photo by Jan Hamilton shows the Bee-fly on one of its favourite nectar sources, the Cuckoo Flower.  It is also fond of Daisies, Dandelions, Primroses and many other spring flowers.  In gardens it enjoys visiting Drumstick Primulas.
 

According to Stubbs and Drake (British Soldierflies and their Allies, 2001), the Dark-edged Bee-fly "cannot fly when the temperature is less than about 17°C"  Here in Argyll they fly at much lower temperatures than that, provided the sun is shining.
 

Bee-flies scatter their eggs on the ground in places where solitary bees or wasps are likely to make their burrows.  This strategy seems just as effective as that of other Bee-fly species that deliberately target existing burrows, which presumably brings a higher success rate per egg but costs time and energy to do.  When the Bee-fly larva emerges it looks around for a burrow and if it is very lucky it finds one within range, whereupon it crawls inside and feeds on the solitary bee or wasp's larva.

Solitary bees and wasps are not particularly common in our area, compared to places further south or east with drier soils, and the Bee-fly's random method of egg-laying may seem hopelessly optimistic, but it obviously works as the Bee-fly population here is thriving.
 

There is still a lot to be discovered about the lifestyle of the Bee-fly, particularly in our area where it may be different from elsewhere, as evidenced by its tolerance of lower temperatures here.  Any observations of Bee-flies will be of great interest, including flowers visited, weather conditions, courtship and mating behaviour and particularly the places where eggs are laid, if you are lucky enough to see this happen, and notes on any solitary bees or wasps that nest in the place where the Bee-fly eggs were laid.

Please send in your Bee-fly sightings using the form below, or email sightings@lnhg.org.uk with the details if you prefer.  If you are not sure of the identity of your insect, please send a photo to sightings@lnhg.org.uk, or put one on the LNHG Facebook page.