Plocamostethus planiusculus

Carabidae  : Harpalinae  : Pterostichini

This large predatory ground beetle is certainly common in the forests of the lower half of the North Island and especially so in the forests of north-west Nelson and Marlborough Sounds. However it rarely enters urban habitats. In Nelson-Marlborough its southeastern boundary follows closely the Great Alpine Fault and although there may be forest on either side of the faultline this beetle rarely crosses it and occupy a seemingly identical habitat. Its southern boundary in northern Westland is also an environmental enigma as there is no vegetational or distinct climatic change associated with that boundary.

A close relative P. scribae is found on the other side of the Great Alpine Fault some 420 km to the south, on Secretary Island, Fiordland National Park perhaps indicating that the two species arose as as the two sides of the fault separated. This is complicated by the glaciation in Fiordland with ice obliterating all habitats there during the Pleistocene.

Text updated: 26/08/2012