St Mark's Flies

St Mark's Fly Bibio marci , also known as Hawthorn flies, are true flies about 12 mm in length. They are named after St Marks day, 25th April, when they they first appear with amazing regularity, and hang around from April - June. When airborne, often in large clouds, 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. These two, a male (top) and a female (bottom) are busy making additional St Marks's flies.