St Marks Fly: Bibio marci

St Marks day is the 25th April and it is about then that this fly emerges as an adult and can be seen in woodland across Dorset. That is where it gets its name from, St Marks Fly or Bibio marci.

It is quite a common insect of the spring and quite often will be seen in large numbers. They are quite distinctive when in flight as their legs hang down and when the weather is cooler or shady they rest on leaves as they await for the warmth of the sun to get them going again.They are jet black with big brown eyes and, overall, have a glossy appearance.

They are only active for about three weeks and then they are gone. They lay their eggs in leaf litter and rotting vegeatation and this is where the larva spends its life, helping to break down the leaves on the woodland floor.

Find out more about the nature of Dorset at Marks Fly

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