At full development, the caterpillar reaches 6 mm long and 1 mm wide. The pupa measures 4.5 mm long. The head section is prolonged on the dorsal surface by a median lanceolate appendage. The cremaster is forked. In the spring, the larva pupates 28 to 45 days after hatching, but only after several months in the case of the overwintering generation.
Mining progressively spreads.
The caterpillar passes through 2 instars and through a prepupal phase prior to pupation . The pupa, supported on its cremaster, perforates the upper epidermis of the leaf with its head spur and remains partly attached until adult emergence. L ife Cycle 3 generations each year, one overwintering in the larval stage. D amage Mining may occupy most of the lamina of infested leaves but damage only erarely causes economically important losses.