This would most likely take more effort than it is worth to put into the game, but I have an idea for level 1.2. It would be a nice detail if the formica sanguinea raids would arrive with some formica fusca soldiers mixed in.
As far as I know the fusca slaves don't take parts in the raids. They stay in the nest and take care of the slavekeepers' brood (and occasionally they start a rebellion where they cut apart parts of the sanguinea brood).
According to the Wikipedia article about Formica sanguinea, slaves have been observed carrying back brood from other colonies, even their own original colony. Again, it’s just a thought, and not something I recommend the team does until they’ve got the leaf cutters ready.