Last modified: Feb. 18, 2020, 10:42 a.m.
Used to be a rare and fragmented species in Belgium but nowadays fairly common throughout the country.
The larva starts mining the petiole and forms a elongated blotch in the base of the leaf usually between leaf margin and the first big lateral vein. The black frass is deposited on either side of the mine in two black lines.
See also bladmineerders.be
Pupates outside the mine in a reddish brown to dark brown cocoon on the ground.
The adults fly in one generations a year during May and June.