The upper epidermis turns white and makes the mines very noticeable at a distance.

Cells display pagetoid growth when they invade the upper epidermis from below.

When the imago emerges the pupa case is thrust through the upper epidermis.

Older larvae start eating parts of the upper epidermis.

The leaf tissue is eaten away up to the upper epidermis.

They eat the folded leaf from the inside, leaving the upper epidermis untouched.

Full-grown larvae split the upper epidermis of the leaf to leave the mine.

They then feed on the upper epidermis within the fold until the leaf falls down.

The upper epidermis of the mine is brownish, with a longitudinal, strong wrinkle at maturity.

The brown frass is glued to the upper epidermis, only leaving the sides transparent.