New Zealand’s insects are usually active year-round. The surrounding oceans temper the climate and contribute to regular rainfall. Winters are relatively mild, and many forest trees are evergreen. Only a few insects in New Zealand need a dormant phase (diapause) to withstand winter.
Some subterranean larvae are most active in winter. These include grubs of the chafer beetle (Costelytra zealandica, or grass grub) and caterpillars of the Wiseana moth (porina caterpillars). Both are native insects which have become pests, because the larvae feed on introduced pasture and clovers.
Surviving an unpredictable climate
Some of New Zealand’s insects have adapted to survive the unpredictable climate. Copper butterflies (genus Lycaena) produce broods made up of normally developing and diapausing larvae (which stop growing for many months). If the normal larvae die off in bad weather, the diapausing larvae will replace them. Alpine wētā can freeze solid over winter and thaw out when the weather improves.