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

Abstract

The New Zealand diving beetle Rhantus plantaris Sharp, 1882 (Coleoptera: Dytiscidae), although comparatively large (10.0–10.5 mm), has not been reported since its description. Until this publication, only the male holotype was 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 roadside pond at about sea level. Collection details and distributional notes are given for the rare south western Australian species Rhantus simulans Régimbart, 1908 which appears to be a peatland swamp specialist. An illustrated key to the New Zealand and Australian Rhantus species is included.