Unusual Italian records witnessing the active flight of two predaceous diving beetles, Rhantus suturalis (W. S. Macleay, 1825) and Acilius (Acilius) sulcatus (Linnaeus, 1758), are provided. The second species is recorded from the Aosta Valley region (N Italy) and from three northern Italian provinces (Asti, Padua, Sondrio) for the first time. The conservation status in Italy of both species is updated. Deronectes silphoides (Ponza, 1805), from the environs of Saluzzo in the Piedmont region (N Italy), was in the past treated as a nomen dubium. Later it was placed, as a nomen oblitum, in synonymy with D. opatrinus (Germar, 1824) (nomen protectum). However, it is herein newly declared a nomen dubium and removed from the above synonymy, since its type specimen is lost and its type locality is outside the area of distribution of the D. opatrinus species-group. At the same time, the identity of Hydroporus silphoides Villa & Villa, 1833 (nomen nudum), previously referred to H. obscurus Sturm, 1835, is declared as uncertain.