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Dotted Bee-fly

Fast Facts

Latin name: Bombylius discolor

Notable feature: In Britain there are four species of bee-fly in the genus Bombylius, with the Dotted Bee-fly being most easily identified by the spots on its wings. These will only be visible when it stops flying. When in flight, their darting movements mean they are difficult to tell from a bee, however, their buzz is far more high pitch, akin to that of a mosquito.

Conservation Status: Not Evaluated

Where in the UK: Dotted Bee-fly is a widespread but localised species in southern England and southeast Wales and can be found in a variety of open habitats. It is considered Least Concern and Nationally Scarce but is rather rare in Devon and much of the South West. Within Devon, scattered records exist along the south coast, but it is most commonly seen between Prawle Point and Start Point.

Dotted Bee-fly (Bombylius discolor) ©️ Smudge 9000 (Flickr, CC BY-SA 2.0)

The Dotted Bee-fly (Bombylius discolor) has a long, almost sword-like, proboscis extending forward from the head, which it uses to feed on nectar, often doing so while hovering over the flowers. Their furry thoraxes and abdomens are a mix of chestnut and black. Female Dotted Bee-flies also have a line of white spots on their abdomens. Lastly, their spotted wings make them easily identified if you are lucky enough to catch one taking a rest.

    • Size: Typically, a length of 8–12mm without inclusion of the proboscis.
    • Life span: Unknown.
    • Diet: The Dotted Bee-fly’s long sword-like proboscis allows it to feed on nectar from a wide variety of flowering plants, particularly early flowering plants. However, it’s ‘sword’ has another use, as sometimes bee-flies stab through the bottom of a flower as a quick and dirty shortcut to get the nectar. They are sometimes referred to as ‘flower thieves’ because when they do this, they take the flower’s nectar without pollinating the flower, how rude!
    • Reproduction: Female Dotted Bee-flies lay their eggs into the nests of solitary mining bees in the family Andrena, especially the Yellow-legged Mining-bee (Andrena flavipes) and The Ashy Mining Bee (Andrena cineraria). The female does this by scooping up sand and gravel with her abdomen, to coat, protect, and camouflage the eggs. She then flies over a solitary bee’s nest hole and flicks her eggs, much like dropping a bomb, hoping they will hatch near or in the nest. When the eggs hatch, the bee-fly larvae use tiny false legs to wriggle into the bee’s burrow where they gorge upon all the pollen provisioned for the bee’s larvae. The bee-fly larvae then undergo a second metamorphosis, called hyper-metamorphosis, which is very rare in the insect world. In this second, much larger, stronger, and hungrier larval state, the bee-fly larva then sets about devouring all of the helpless solitary bee larvae until it is the only grub remaining in the nest.
    • When to see: March-June, most frequent in April.
    • Population Trend: Unknown.
    • Threats: Habitat loss, and declining populations of their host solitary bee species due to habitat loss.
    • Fun Fact: Bee-flies do not have a negative impact on solitary bee populations or their other hosts, and parasitism is all part of a healthy ecosystem. In fact, the Dotted Bee-fly is one of the many parasitic insects that make up an estimated 40% of all described insect species.

    How you can help:

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    Join a recording scheme and log your finds – submit any recordings/sightings through the iRecord or iNaturalist apps to help us further understand the distribution of this species.

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