The caterpillars feed on grasses from the time they emerge in autumn or early winter until spring. They are rarely seen as they feed at night, or occasionally by day, if conditions are cool and damp. These holes are entries into web-lined, vertica burrows that usually contain a fresh blade of grass above the caterpillar and green droppings at the base. Throughout spring and summer the caterpillars do not feed but survive in their burrows on fat reserves. In autumn there is a short pupal stage after which the adults emerge.
Webworm therefore has only one generation per year.