Cockchafers spend most of their lives (3 or 4 years) underground as larvae, or grubs. The grubs are white and C-shaped with 6 legs and reddish-brown heads. They can be larger than the adults, growing to up to 40mm and are a food source for owls and bats. The larvae eat the roots of a wide variety of plants and in large numbers can become pests damaging pastures and crops.