cockchafer, (Melolontha melolontha), a large European beetle that is destructive to foliage, flowers, and fruit as an adult and to plant roots as a larva. In the British Isles, the name “cockchafer” refers more broadly to any of the beetles in the subfamily Melolonthinae (family Scarabaeidae), which are known in North America as June beetles, June bugs, or May beetles. See also chafer; June beetle.