New galls of the California Gall Wasp. These are under 1-inch in diameter, which at maturity can be over 3-inches and persist on the tree for several years. The largest gall in the western states and one of the largest flies at about 5mm, of which only parthenogenetic females are known. All of the western white oaks serve as host.
2011-12-03 Lower Austria, district Bruck/Leitha - Braunsberg northern flank (180 msm Quadrant 7867/2).Gall on Quercus (most likely Quercus pubescens).According to a monograph written in German by Gustav L. Mayr, Die mitteleuropischen Eichengallen in Wort und Bild (Jahresb[uch] d[er] Rossauer Communal-Oberrealschule, Wien - Vienna 1870-71) this oak apple = gall should be one from Cynips caput-medusae; the species obviously has been renamed (see remark of treegrow below) to Andricus caputmedusae.(Compare also photo of same species here.)