Adult male St. Mark's (Bibio marci) fly resting on a leaf. This fly is found across much of Europe. St. Mark's flies are so called because they emerge around St Mark?™s Day, 25th April, every year. They are black and shiny; the male has large eyes divided by a groove, while the female has a small head with tiny eyes. Large numbers of adult St. Mark's flies can be found in woodland edges, hedgerows, fields and wetlands. They feed on nectar and are important pollinators for fruit trees and other plants. Photographed in April, in Dorset, UK.