The bright green caterpillars (the larvae) are leaf-miners. They create a channel between the upper and lower surfaces of a leaf, and are found in August and early September.
This species mines leaves of the sessile oak - Quercus petraea. Empty mines were also found on the pedunculate oak - Quercus robor.
Most of the specimens came from saplings, seedlings and low growth.
The caterpillar is extremely flattened.
The mine consists of a short, highly contorted gallery filled with black frass - the droppings produced by burrowing insects.
The mine suddenly enlarges into an elongate blotch, with frass concentrated in two lines along the edges.
Adults are on wing from April to May.
There is one generation per year.