Zosmenus quadratus Fieber, 1844: 31. NT (Heiss & Péricart, 1975: 535): male (macr.), Italy, Triest; NHMW.
?Acanthia clavicornis (non Linnaeus, 1758): Fabricius, 1775: 694. Misidentification (see Reuter, 1888a: 218; Heiss & Péricart, 1975: 523).
Zosmenus dilatatus Jakovlev, 1873: 28 (syn. Horváth, 1906a: 6). LT (Heiss & Péricart, 1975: 523): female (brach.), Russia (ST), Astrachan [= Astrakhan]; ZMAS.
Zosmenus convexicollis Jakovlev, 1873: 29 (syn. Heiss & Péricart, 1975: 537). HT: female (brach.), Russia (ST), Sarepta [= Krasnoarmeysk, nr Volgograd]; ZMAS (Heiss & Péricart, 1975: 524).
Piesma quadratum var. rotundicollis Rey, 1888a: 189 (upgraded to species by Wagner, 1953m: 68; syn. Heiss & Péricart, 1975: 525, 537). LT (Heiss & Péricart, 1975: 523): male (macr.), France (Var or Alpes-Maritimes); NHML.
Piesma quadratum var. nigroscutellata Péneau, 1921: 57. ST(S): France (Île de Ré); lost (see Heiss & Péricart, 1975: 523).
Piesma quadratum f. ruda Jordan, 1953: 8. ST(S): Germany (Saxonia); lost? (see Heiss & Péricart, 1975: 523).
Piesma chinianum Drake & Maa, 1953: 87 (syn. Heiss & Péricart, 1983: 111). HT: female (submacr.), China (SE), Canton [= Guangzhou] (see Heiss & Péricart, 1983: 119); USNM.
Piesma suaedae Wagner, 1954ab: 5 (syn. Heiss & Péricart, 1975: 525, 537). HT: male, Croatia, Dalmatia, Kaštel Lukšić; ZMUH.
Piesma spergulariae Woodroffe, 1966b: 107 (downgraded to subspecies by Heiss & Péricart, 1975: 537; syn. Heiss & Péricart, 1983: 111). HT: male, Great Britain (Scilly Is); BMNH.