Essentially an upper- or (more commonly) lower-surface blotch mine, usually made by a Gracillariidae larva. The larva lines the interior of the mine wit silk; the silk gradually shrinks, causing the mine to bulge. Because the mine is not full depth both sides of the leaf behave differently then. The non-eaten leaf tissue because of its stiffness bulges up relatively little; the epidermis of the other side of the mine contracts much more strongly. Depending on the species one longitudinal fold may develop, or several lesser folds, or even a multitude of very fine folds.