The females of these wasps insert their ovipositor between the abdominal plates of the ladybird and lay one egg inside the host's body cavity. When the wasp larva hatches it proceeds to eat any other parasite eggs it finds within the host and then starts eating the host's internal organs. When the larva is ready to pupate it immobilizes the still living host by biting through the nerves that control its legs. The larva then makes a hole in the underside of the host, emerges, and spins a protective cocoon which remains attached to the underside of the ladybird, presumably to protect the developing wasp from predators and parasites that might attack it.
Photo taken the Wilderness, Whiteknights Park, Reading, UK, on 2012-05-24.