Last modified: April 23, 2019, 12:44 p.m.
The egg is deposited on the underside of the leaf.
The mine starts as a very contorted gallery allmost completely filled with redbrown coiled frass. Suddenly the pattern of the frass changes from coiled to scattered also the colour changes from redbrown to black. Further on the mine widens into a large irregular blotch.
See also bladmineerders.be
The cocoon is black and is spun amongst leaf litter.
The adults only have one generation a year and are on the wing from the end of May until July.