Larvae produce a "blotch mine" on leaf and the leaf is often folded, then tied on with silk and then they feed. They usually pupate in their mines.
Some (all?) are hypermetamorphic
. The first stages are a flattened larva without properly developed legs, and with highly modified mandibles, generally "scissor-like" shaped. They serve to saw the plant tissue, separating the cuticle from the epidermis. These early stages are sap feeding. The second developmental stages have the typical caterpillar shape of Lepidoptera, with legs and prolegs, with a spinneret and well-developed chewing mmouth parts to feed on tissues. This larval stage has been called a "tissue feeding form" Trägardh, I. 1913. Contributions towards the comparative morphology of the trophi of the lepidopterous leaf-miners. Arkiv för Zoologi 8: 148