Would someone please id this one for me please -
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Name reflects the fact that its emergence normally occurs on or around the feast day of St Mark which is April 25th.
It's always useful to know the size of Bibio flies, as there are some smaller species that look similar to B. marci, but the wing venation and very hairy eyes are a good match so I think the ID is correct. The key to this group of flies uses the length of the wings as its size measurement.
Entomologist and biological recorder
Lat/Lng: 52.1307, -1.8597
OS grid ref: SP096480