This aliens are battle oriented only. They are small as a fist, have little brain, some toxin glands and superconductor magnetic field organs inside them(to levitate).
They live for battlefield. Usually they are swarmed to be more intelligent (XVI), swarming also makes it easier to levitate for them. It's hard to kill them with bullet/laser/etc weapons, so you'll need flamethrower or grenades to kill them all. If shot by point-target weapons swarm just becomes weaker