Fossil beetles from two last interglacial lake deposits from southern Wairarapa, central New Zealand are provisionally ascribed to marine oxygen isotope stages (MIS) 5a–e. Both assemblages represent ecological successions from lake margins to forest. The lower sample (MIS 5e) is characterized by species found today in northern New Zealand. These species, including Lorelus crassicornis, ‘Dasytes’ laticeps, Cryptobius nitidius, ‘Stenomalium’ sulcithorax, Psilocnaeia nana, and Microbrontes lineatus, represent a southward displacement from modern distributions by up to 700 km. Climate reconstruction indicates that temperatures at the time of deposition were 1.6–2.5°C warmer in the summer (January) and 2.3–3.2°C warmer in the winter (July) than at present. These results match local and regional pollen and phytolith findings of warmer, wetter conditions at the thermal maximum of the last interglaciation. In contrast, the upper sample is characterized by species that have widespread modern-day distributions. This indicates that modern conditions were attained later in MIS5, after the MIS 5e thermal maximum.

A series of 18 fossil beetle assemblages are used to reconstruct the paleoenvironment of the northwest West Coast, New Zealand, over the period of the last interstadial–stadial transition (ca. 37,000–21,300 cal yr BP). The samples were recovered from an in-filled hollow within a dune field ca. 9 km south west of Westport (41°47′S, 171°30′E). This fossil beetle reconstruction is compared to an existing palynological reconstruction from the same site. The beetle assemblages indicate an environment of marshy shrubland interspersed with closed canopy coastal vegetation prior to glacial onset, and a mosaic of closed canopy patches and open tussock grassland during full glacial conditions. These interpretations, contrast with the palynologically based interpretation which indicates subalpine shrubland prior to glacial onset and widespread grassland with little woody vegetation during the period of maximum glacial cooling. This study is consistent with other non-pollen studies in New Zealand and indicates that the palynological interpretation of the paleoenvironment of the Westport region downplays the importance of closed canopy vegetation in the area during the transition from interstadial to full glacial (stadial) conditions. It challenges the interpretation of open vegetation at low elevations during glacial periods from pollen studies.