Leaf miners on an oak. It isn't very clear in the photo, but the larva was visible (I saw it wiggle).
larval mine on Hazel
On Hazel, Corylus avellana.
larval mine on Hazel
upper surface blister mine on Hazel
On Hazel, Corylus avellana
larval mine on Hazel
On Corylus avellana.
larval mines on Hazel
larval mines on Hazel
top-surface larval blister mines on Hazel
larval mines on Hazel
larval mines on Hazel
vacated larval mine on Hazel
larval mines on Hazel
larval mines on Hazel
larval mines on Hazel