St Mark’s Fly

Home|Insects|St Mark’s Fly

St Mark’s Fly

Common name :  St. Mark’s Fly

Latin:   Bibio marci        Family:

  1. Season: Spring StMark,s day 25th April
  2. Size: 10-15mm
  3. Larval Food: Breeds in soil and rotting vegetation
  4. Status : Most of europe
  5. Biomap:


Location :    Wicklow, Carrig Mill ,Greystones  Farrankelly main field on Willow.


Wildlife relationships:Pussy Willow, Gorse

When I first recorded this insect, I couldn’t believe how dark a black could be but nature created this in the body of St Mark’s Fly. It is a true black as you would say in painting like a rich Ivory Black. Here it is recorded on decaying Gorse in Carrig Mills Greystones. I also recorded these flies on mass in the Farrankelly field (Delgany) feeding on the nectar of Pussy Willow. This area is a minor flood plain with 3 large undeveloped fields and a beautiful riparian way on the Three Trout stream.

Bio data

Bibio marci or St. Mark’s fly or Hawthorn Fly is a species of fly from the family Bibionidae. It is found across much of Europe. Their common name comes from the fact that the adults usually emerge around St Mark‘s Day, 25 April.


Like most bibionid larvae, they grow up in grassy areas and are herbivores and scavengers feeding on dead vegetation or living plant roots. Bibio marci larvae are known to be root damage pests of celeryasparagusrosessaxifrageslawn grasslettuce and Polyanthus. They also feed on a very large number of plant species that are commercially unimportant.


Go to Top