First of all, sorry for what is a post about getting rid of ants in a forum dedicated to keeping ants, but I figure this is where the knowledge resides. I am actually quite fond of ants, and have kept Lasius niger in the past - yet this time their presence is unwanted and I would very much appreciate advice on how to best make them leave my apartment for good.
Long story short, I moved into a new apartment in the middle of Berlin (Germany) last September. In spring I first noticed an ant-trail in my living room, running from under the wooden floorboards near my balcony door (2nd floor, so quite high off the ground in a 6-storey, 100 year old apartment building) to some uneaten pizza that was lying around (I have since stopped doing that). At the time it was enough to clean the room and lay out some ant traps - the ants mostly disappeared for the next few months. Early summer they came back though, but this time a borax-sugar combination I read about online was enough for them to again mostly disappear, with just a few wandering around now and then). Then a few days ago: nuptial flight. I had noticed an uptick in the amount of ants leading up to this, but the flight itself is ongoing (day 4) and pretty wild in the evening and night, the number of virgin queens flying around must be in the hundreds, not to mention a large number of males both flying and walking.
I had pest-control come by the apartment yesterday daytime, when activity was very low. She squirted some gel (wish I could say which kind, not sure) near to where the ants are appearing from the floorboards, and told me to call again in 2-3 days to repeat the process if the ants were still there. It has only been 24 hours, but the ants are very much there - and I don't think the person I had over knew much about nuptial flight, its scale, or whether this had any impact on how she should be dealing with the situation.
My questions I guess are how to best deal with this situation, during flight, but also how to get rid of this colony over the long term. Having a huge nest underneath my floorboards is not really viable.
I've attached some photos of the species in question. Many thanks for any help and guidance.