The systematics of New Guinean Colymbetini is revised. All of the species a
re montane and/or subalpine, and include: Carabdytes upin Balke, Hendrich &
Wewalka, 1992; Rhantus suturalis (MacLeay, 1825) s.l.; R. papuanus Balfour
-Browne, 1939; and R. ekari Balke & Hendrich, 1992a. The following new spec
ies are described: R. anggi, sp. nov.; R. bacchusi, sp. nov.; R. dani, sp.
nov.; R. kakapupu, sp. nov.; R. riedeli, sp. nov.; and R. supranubicus, sp.
nov. Rhantus neoguinensis Gueorguiev & Rocchi, 1993 is a junior subjective
synonym of R. suturalis s.l. All New Guinean Rhantus Dejean, 1833 belong t
o the monophyletic R. suturalis-group. Within that group, Rhantus simulans
Regimbart, 1908 (southwest Australia), R. dani, R. suturalis, R. ekari and
R. kakapupu form a monophyletic subgroup; the latter two are sister-species
. The R. suturalis-group is suggested to be of Holarctic origin. Possible s
cenarios that may explain the biogeographical history of this tribe in the
Indo-Australian region are discussed. No evidence was found for monophyly o
f New Guinean Rhantus. The biogeographical history of Carabdytes upin remai
ns enigmatic. New Guinean Rhantus inhabit swamps at lakeshores, ponds and d
itches, while C. upin Balke et al., 1992 is a rheobiont. A checklist of wor
ld species of the R. suturalis-group is provided.