This graceful little moth belongs to a family with an appropiate name: Gracillariidae. The larvae of many species live inside leaves all their lives, or at least during the first stages. Caloptilia alchimiella below for instance mines the leaves of oak. Half-grown it gets to the outside of the leaves. It will fold a leaf up into a cone, in which it will spend the rest of its life. Caloptilia alchimiella is on the wing from May to August and is very common in woods containing oak. There is a look-a-like species: Caloptilia robustella and it is very hard to tell the two apart. Both will reach a wingspan of 10 to 13 mm.