1a epidermal, silvery, lower- or upper-surface corridor, eventually widened to a blotch; the older larva lives free in a leaf roll: Caloptilia roscipennella

1b full depth blotch, finally with an oval excision => 2

2a mines all over the leaf; frass dispersed in the mine; larva pale rust-coloured: Coptodisca lucifluella

2b mines in the angle between midrib and side veins; frass in a clump (invisible from above), larva off-white, partly yellow: Coptodisca juglandiella