From Microleps.org found here
: "Tischeria quercitella (Fig. 1) makes a distinctive upperside blotch mine on oaks of the black oak group. According to Braun (1972), it is the only species of the oak-feeding group that constructs a nidus (the circular, central part of the mine seen in Fig. 1) as a pupal chamber within the mine. In the adult, the patch of blackish scales at the tornus of the forewing is diagnostic for T. quercitella, among Fagaceae-feeding tischeriid species that occur in Illinois."