Biology and behaviour

The complete lifecycle of cockchafers from egg to adult is usually 3-4 years.


The grubs (commonly called white grubs) hatch from the eggs in about 5-6 weeks and can grow to 40mm in length when fully mature.

They can be eaten by rooks, crows and gulls if exposed by ploughing.

The grubs live for 3 years and usually turn into pupae at the end of their third summer. They then change into adults and stay underground during the winter and emerge in the following year.


The adults emerge from the soil and fly towards trees to gather together and mate. Fertilised females fly back to the open treeless areas from where they emerged and burrow underground in order to lay their eggs on roots.

Adults are active fliers at dusk onwards. They feed on leaves after dark and rest on trees during the day.

They only live for about a month in all and can be eaten by owls and bats.