Aliens aren't ants, they aren't from earth, they might not even be naturally evolved organisms.
So giving 'ant hives fight' as a reason for aliens doing the same is crap.
There is no in-film evidence to show what aliens from seperate hives will do when they meet.
I think how they'd act really depends on what the aliens' origins are.
If they were actually engineered for use as weapons, they probably wouldn't fight, as it would be counter-productive to the aim of destroying the life they have been seeded amongst.
However, if they evolved, it seems much more possible that they would fight between hives, for hosts, land or whatever else they might want.
