wtf would colonise a rock 'devoid of life' - they really needed a fat replicator if they tried thatIs there any evidence that the xenomorphs were native to the planet? The humans were colonists and I assume they expected LV-426 to be devoid of life (they didn't realize they were sent there with ulterior motives).
The xenomorphs don't appear to have a society per se (is there ever any evidence of one?), so it's hard for me to believe that they would intentionally colonize so much as infest.