St Mark's Fly - Bibio marci

Alternative names
Hawthorn Fly

The male is about 12 mm and the female 14 mm. This is quite a hairy black insect. The males have large bulbous eyes and a rather tubular segmented body and black legs. The females have smoky wings and much a smaller head and eyes. The front legs have a stout spine at the tip of the tibia.

Similar Species

Other Bibio species are broadly similar, though B. marci is larger than most.

Identification difficulty

Hedgerows and woodland edge, often in moist areas.

When to see it

Named after St. Marks day, 25th April, when they appear with amazing regularity. April - June.

Life History

When airborne, they fly in a sluggish manner above hedgerows and grass, with their long legs dangling down. The larvae feed on grass roots, leaf mould and decaying matter.

UK Status

Common and widespread in Britain.

VC55 Status

Common in Leicestershire and Rutland

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Leicestershire & Rutland Map


Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map