Andricus chrysolepidicola (bisexual generation)

This gall is a single celled, thin walled, light brown bud-shaped gall (fig. 1) which develops on a number of different bud elements: the base of the bud scale, on the stem of the male inflorescence as part of the male flowers, at the base of a developing leaf stem or new twig.

Photo caption:
Fig. 1. Three photographs of the spring gall of Andricus chrysolepidicola (Ashmead). The size of each gall is about 2.0 mm. The first two (left and middle) arise from the stem on which the male flowers (here shriveled by being dried out) develop. The last (right) shows the gall as a swelling at the base of a bud scale.

- DJ Burdick : (1967) Oviposition behavior and galls of Andricus chrysolepidicola (Ashmead)^©

Reference: https://www.biodiversitylibrary.org/page/53644798#page/263/mode/1up