Around here it is the wet that drives them out of the nests on the ground and into anything dry and up....once I had them in the mailbox down at the end of the drive....Now I know there was never any food in there. I think when the climate changes just enough to disrupt their nests they seek new territory and unfortunately that can mean our homes...added bonus is food. I finally had to spray around the base of the house. You will not get rid of the ants by killing the workers...you have to find the queen. Oh dear this sounds like a bad SiFi flick....