Rediscovery of the New Zealand diving beetle Rhantus plantaris Sharp, and notes on the south west Australian R. simulans Regimbart, with an identification key (Coleoptera : Dytiscidae)

The New Zealand diving beetle Rhantus plantaris Sharp, 1882 (Coleoptera: Dy tiscidae), although comparatively large (10.0-10.5 mm), has not been report ed since its description. Until this publication, only the male holotype wa s known. It has been questioned whether this species was a part of the New Zealand fauna. The rediscovery of the species is reported, based on a small series collected from near Christchurch. The specimens were taken from a r oadside pond at about sea level. Collection details and distributional note s are given for the rare south western Australian species Rhantus simulans Regimbart, 1908 which appears to be a peatland swamp specialist. An illustr ated key to the New Zealand and Australian Rhantus species is included.