A small family of tiny moths. Systematically they are close to the root of Lepidoptera evolution, because of the possession of rudiments of the mandible; these are still fully developed in the pupal stage. The British species are treated by Heath (1976a).
Most species live on Birch. The mines of most species occur in early spring. The females have an ovipositor, enabling them the insert the egg in the plant tissue. The larvae make blotch mines that are conspicuous because the frass is in very long, almost continuous, threads. Mature larvae leave the mine and pupate in the ground. They remain as a pupa untill the next very early spring. (For that reason they are notoriously difficult the breed.)
De larvae are colourless, and lack thoracic and abdominal feet. There is but one stemma in the eyepatch.
Common (1975a), Davis (1987a), Heath (1976a).