Episode 19's title is "Sortie in the System"... what system? Solar System or what?
EDIT: About episode 18... I think the Iron Tribe should have destroyed Taro. Bronze Tribe didn't have so much problem in wiping out the humans from the Earth, countless lifes were lost because of the Bronze Tribe. I don't share that crappy "politically correct" principle Deianeira is boosting: who cares if that planet was only the place where the bugs were born. In the future those bugs would have become enemies and so destroying them is only obvious: without a place where they're born the Bronze Tribe would become history sooner or later. The same thing stands for the Silver Tribe, of course: guys who are willingly in committing a genocide deserve only death and by the way this is a war to enstabilish who will rule the galaxy and two rulers aren't possible.