Definition of St Mark's fly in English:

St Mark's fly

noun

  • A dark European fly which first appears around St Mark's Day (April 25th). It drifts slowly over low vegetation with the legs hanging down.

    • ‘Look in an orchard around St Mark's Day, 25th April, and you are likely to see many insects including St Mark's Flies, largish black insects drifting lazily about with long legs dangling.’
    • ‘Despite their name St. Mark's Flies (also known as Fever Flies) are mosquitoes and not flies. The females usually have small eyes, but the males have very big eyes indeed and that's why they're called flies.’