imperceptibly: P. and V. λάθρα.
craftily: Ar. and V. δόλῳ, V. σὺν δόλῳ, ἐν δόλῳ.
enter insidiously (of diseases, etc.): P. and V. ὑπορρεῖν.
treacherously: P. ἐξ ἐπιβουλῆς.
