Wing disks are very small until the last larval instar, when they increase dramatically in size, are invaded by branching tracheae from the wing base that precede the formation of the wing veins, and begin to express molecular markers in patterns associated with several landmarks of the wing. Near pupation the wings are forced outside the epidermis under pressure from the hemolymph, and although they are initially quite flexible and fragile, by the time the pupa breaks free of the larval cuticle they have adhered tightly to the outer cuticle of the pupa (in obtect pupae). Within hours the wings form a cuticle so hard and well-joined to the body that pupae can be picked up and handled without damage to the wings.
The larvae mainly feed on leaves of flowering plants. They are very specific in their feeding habits and will usually only feed on a few closely related plant species. Larvae recognize their host plants by certain aromatic vegetable oils, which they contain. It is generally believed that selection may depend upon the detection of chemical attractants in the food species and of repellents in others.