Until April 2009 broodlings were created by swarm guardian attacks; every time the swarm guardian attacked, it spawned a pair of broodlings which lasted only a few seconds. The broodlings are very weak. They spawned when buildings were attacked as well. The ability was moved to the brood lord. In May 2008 builds, broodlings were created from infested terran and protoss structures, which were created when an infestor infested the buildings. In these cases, the broodlings have been replaced by infested marines and before their cancellation, infested protoss respectively.