Holcaspis bessatica, Holcaspis bidentella, Holcaspis abdita, Holcaspis falcis, Holcaspis ohauensis and Holcaspis new species are six rare species that are confined to the Mackenzie basin and its surrounding mountains. Holcaspis bathanae has only two known populations, of which one is in the basin (see its notes). Two other widespread species, Holcaspis angustula and Holcaspis sternalis and possibly a third, have local populations.