Introduction of the Exocelinacasuarina-group, with a key to its representatives and descriptions of 19 new species from New Guinea (Coleoptera, Dytiscidae, Copelatinae)

Abstract. Nineteen new species of Exocelina Broun, 1886 from New Guinea are described herein: E.adelbertensissp. n., E.ambuasp. n., E.bewanisp. n., E.cyclopssp. n., E.ibalimisp. n., E.kekisp. n., E.kumulensissp. n., E.mendiensissp. n., E.menyamyasp. n., E.okapasp. n., E.piusisp. n., E.pseudofumesp. n., E.pseudopusillasp. n., E.pusillasp. n., E.simasp. n., E.simbaiensissp. n., E.simbaijimisp. n., E.sumokedisp. n., and E.yoginofisp. n. All of them, together with five already described species, have been united into the newly defined casuarina-group, a polyphyletic complex of related species with similar shape of the median lobe and paramere setation. An identification key to all known species of the group is provided, and important diagnostic characters (habitus, color, male protarsomeres 4–5, median lobes, and parameres) are illustrated. Data on the distribution of the species are given, showing that most of the species occur in the central, mountain part of Papua New Guinea.