This may be the first time someone actually has wanted to have a low number of systems, which I am fine with. The issue is your population, I understand you a bug hivemind and having a large population makes sense, but you still have to but all those bugs somewhere and 12 systemes doesn't seem like enough to support 1 trillion of anything for a very long time. But if you want to RP that, I suppose its accepted.
The number of systems doesn't matter because a star system is a big place. And one trillion things can easily be put in twelve of them among planets, desolate moons, and massive fleets of ships. And in a setting like space, territory doesn't mean much. It's just a concept. Because you can't really secure a region of space like you can secure a region of planet.
You'd have to keep in mind. That's just where people would mark their territory, somewhere you'd walk into with a 100% expectation of seeing them. They would go outside that area in search of food. That's what makes them a fun antagonist, because they're actively finding colonies and ships of others and grabbing them and capturing the people there to eat them and they don't do it out of malice or for power, but just so they can survive as a species. They're basically neutral-evil, because they're always there, but they just want to eat.
The thing is, if a sizable enough civilization knows the rough schedule of when the Vresh would swing by to round up food, and they know about how many people the Vresh usually take, they could get out of it by just sending out a shipload of criminals, malcontents, sick, and wounded every time and be fine. And think, if that civilization is ever attacked and subjugated, they could just not tell the oppressors about that, then they have a fun distraction weapon as the Vresh set upon the planet like locust.




