Capsus quercus Kirschbaum, 1856: 253, 323. LT (Rieger, 1981b: 95): male, Germany, Wiesbaden; MWNH.
Capsus simillimus Kirschbaum, 1856: 253, 325 (syn. Wagner, 1943c: 34). HT: male, Germany, Wiesbaden; MWNH.
Psallus quercus var. montandoni Reuter, 1894: 144. LT (Kerzhner, 1997d: 118): male [not female], Romania, Comana; MZHF.
Psallus simillimus f. basipallens Stichel, 1933: 265. For simillimus var. β in Reuter, 1878a: 119.
Psallus quercus f. fuscata Stichel, 1933: 266 (junior primary homonym of Psallus parshleyi var. fuscatus Knight, 1923). For quercus var. β in Reuter, 1878a: 121.
Psallus quercus f. grisescens Stichel, 1933: 266. For quercus var. γ in Reuter, 1878a: 121.
Psallus quercus f. maculata Stichel, 1933: 266. For quercus var. δ in Reuter, 1878a: 121.