The adult porina moth is the fat brown moth that flies around you lights at night. It lays 100+ eggs on grass in spring and summer. On hatching the caterpillars move to leaf bases where they feed. As they grow they burrow into the soil and emerge at night to feed on leaves. They do most damage in autumn and early winter. Compared to Grass Grub, Porina caterpillar is the more easily controlled pest.
Porina are present throughout most of the country. When porina caterpillars hatch from the eggs, they live in the pasture and pasture litter for about five or six weeks, then burrow vertically into the soil, where they live during the day. At night they come to the surface and eat the grass around the burrow. They reach their full size of about 60–70 millimetres length in about August, when they pupate.