Most of the animal species have developed specific feeding habits, and this applies especially to the larvae of leaf-mining Lepidoptera. The genus Nepticula comprises about 60 species of minute moths. In general, the forewing is purple to black with a transverse, golden or silvery band. Because of this similarity of pattern, it is often impossible to identify many of the species in the adult stage. The larvae mine within the tissues of leaves, usually just beneath the upper epidermis, consuming the palisade layer of cells. Each of the species feeds in a characteristic manner. For example, N. rosaefoliella Clem. forms a serpentine mine usually along the edge of a rose leaf, and N. juglandifoliella Clem. forms a linear mine along a vein. The mine of an undescribed species on elm starts as a semi-serpentine track and abruptly enlarges into a viscera-like blotch; that of another undescribed species on willow terminates in an irregular blotch; and so on. Each species engraves its own symbolic characters, and whoever has learned to read the symbols can readily determine the species that made them.