[.915] Living "dead" unit

Used Pillar of Fire to destroy a band of mites wandering through my territory.  They list as 0/21 hit points, still showing a single animated unit from their group.  Even hitting them again with that spell on the next turn, when they have 2 hit points, only reduces them back to 0--and they still exist.  Plus, they're able to move and destroy outposts (which, supposedly, marauding monsters can't do, per Brad's comment a few days back).  Quitting and reloading a saved game where this is happening removes the 0 HP unit.