ἔγνω δὲ φώρ τε φῶρα καὶ λύκος λύκον → the thief knows the thief and the wolf knows the wolf, and thief knows thief and wolf his fellow wolf, set a thief to catch a thief
P. and V. σπάνιος (Euripides, Fragment), V. σπαρνός, σπανιστός.
