A new species and lectotype designations for New Zealand Hydora (Elmidae: Larainae) with a world checklist

The family Elmidae is represented by a single genus Hydora Broun in New Zealand; they are the most abundant Coleoptera encountered in streams there. There are nine previously described species of Hydora, six from New Zealand, to which we add Hydora musci sp. nov. based on larvae and adults. Hydora musci can be distinguished from all remaining New Zealand species by the following characters: adult with pronotum with weak lateral transverse depression, pronotal lateral carina incomplete extending from posterior margin approximately two-thirds anteriorly, sublateral longitudinal carina less than one-third of the average carina length; elytral punctate striae poorly developed, elytral setae no longer than one-third width of eye, outer surface of mesotibia polished, surface of metatibia not polished; larva with thoracic and abdominal segments bearing single dorsal and lateral protrusions (often reduced), tooth absent on anterior margin of head, laterotergites complete on abdominal segments I and II, complete to incomplete on segments III to IV. Most specimens of H. musci were found in stable tributary streams containing bryophytes in the Arnold River Catchment 31 km inland from Greymouth on the West Coast of the South Island. Larvae are grazers that co-exist with adults at the stream margins and in splash zones associated with bryophytes attached to large boulders. A catalogue of the world Hydora species is included, and lectotypy is established for the following New Zealand species: Hydora subaenea Broun, Hydora picea (Broun), Hydora obsoleta Broun, Hydora nitida Broun, Hydora lanigera Broun and Hydora angusticollis (Pascoe).