The Wirrn were led by a Swarm Leader. (TV: The Ark in Space)
During the first invasion of Earth by the Nestene Consciousness, an energy unit was designated "Swarm Leader", which was vital to creating a Nestene creature: once all units were collected, their contained intelligences were deposited into an environment tank to allow them to manufacture a body out of plastic which would serve as the central brain of the Autons. (TV: Spearhead from Space)