St. Mark's Fly

St. Mark's fly Bibio marci gets its common name from the belief that it always emerges on St. Mark's Day April 25th., which isn't too wide of the mark because swarms of these flies have emerged over the last few days.

They usually hover up and down just above the grass but in this morning's overcast weather literally thousands were resting on the sycamore leaves on the edge of a woodland just south of Durham city.

These flies have remarkable eyes - four in males, which you can read about here and you can find an interesting post by Nyctalus on these common insects, showing one in flight, here.