Head mixed greyish and brown hairs; forewing ground colour brown, four white costal and three white dorsal striae.

First instars greenish white. Later instars greenish yellow with a dark brown or black spot on the dorsal side of each segment. A large blackish spot on the prothoracic segment. Head almost black.

Whitish or silvery tentiform mine on the upperside of a leaf, often with a papery appearance. Later instars cause the leaf to contract strongly, especially when more mines are present on the same leaf. When the mine is situated at the margin of a leaf, the margin can be folded over the mine, thus resembling the mine of Parornix devoniella which lives on the same host plant. The difference is that the caterpillar of Parornix devoniella attaches the folded leaf with external spin, while the contraction of the leaf in Phyllonorycter coryli is caused by spinning inside the mine. The dark frass is contained in a corner of the mine.
See also gracillariidae.net and bladmineerders.be.

A whitish cocoon inside the mine.

Sometimes several eggs are deposited on one leaf, but always on the upperside. The last instar pupates inside the cocoon within the mine. The pupa of the second generation hibernates in the mine, in fallen leaves among leaf litter on the ground. The adults rest during the daytime and come to light.

The monophagous larva lives on Corylus avellana.

Forests, parks and open spaces wherever Corylus avellana is present.