Official text extracted from Panzer Dragoon Orta.
Bio-engineered creatures called Baldors have been domesticated by a rather primitive tribe of people. The appearance of these Baldors has earned their riders the nicknames Wormriders or Bug Herders. Scientists still do not understand how it is that these bio-engineered creatures, originally designed to instinctively view humans as targets, were domesticated.
One theory states that it is not the humans that control these creatures, but rather that the creatures control their riders by emitting some sort of pheromone to influence their actions.