Many wasps make galls in oak trees, and a single oak may have over seventy kinds of gall, each made by a different species. But the hard shell of the gall doesn't always succeed in defending the wasp larvae, because some gall wasps don't make their own galls. Instead the jewel wasp parasitises the galls made by other species. She drills into the gall with a special organ that has a zinc tip. Then she injects an egg directly into the larva inside. Her own larva will eat the resident and take over its home.