Epitrimerus longitarsus (Nalepa, 1897)
over considerable, vaguely delimited parts the leaf is somewhat bulging upwards, somewhat pale or brownish; at the underside gallmites are visible.
These symptoms can be caused by several species of gall midges that, possibly only facultatively, and maybe only in combination with others induce gall formation. See also Acaricalus trinotus, Tegonotus heptacanthus and T. trouessarti.
Buhr (1964b), Ripka (2014a) , Roivaianen (1950a).