Chromatomyia aprilina on Lonicera periclymenum, Voltherbroek
Chromatomyia larvae always pupate inside the mine. Often this happens in a separate part of the mine, a sort of pupal chamber. There the front spiracula penetrate the plant epidermis. Like in all higher Diptera the adult fly leaves the puparium by pumping up a bladder on top of the head. This creates an irregular hole in the puparium wall.
Neither pupation within the mine nor penetrating spiracula are exclusive characters for Chromatomyia: both can be found in some Phytomyza species as well.