Swarms are small flying critters with a habit of attacking Transformers. They build their hives anywhere, including the debris field around Trypticon station and even deep within the fortresses of Iacon and Kaon. Though they're more pest than anything, they can be deadly if there are enough of them, and they grow to the size of a small Transformer.
Swarms were common during the Great War. As Megatron, Dirge and a third Decepticon made their way through Iacon, the red shirt ran ahead and was picked off by a hungry swarm. The creatures would continue to plague the Decepticons as they carried out their evil plans. The Autobots also had problems with the pests—Optimus Prime and Jetfire lost a fellow Autobot to a swarm under conditions similar to the Decepticons' earlier encounter.