I have a problem with ants in my garden. I am usually of a 'live and let live' approach to outdoor creatures, but a nest of large black ants has taken up residence under one of my slab steps in the garden. I had seen them going around the garden and I was not bothered since I had read online that black ants don't bite.

Well, yesterday I sat on the step while I was watering the plants, and the ants swarmed. I didn't notice, since I was facing the other way to them, until I felt something on my hand. Half a dozen of the little so and so's were on me, and one of them was most definitely biting me. It was holding on firmly enough that a blast from the hose on the jet setting at close range did not move it, I had to physically scrape it off. I don't know what these ants are, but they look bigger than typical garden black ants in England. The bite hasn't left a mark on me.

I thought originally that maybe the ants were reacting to the water possibly flooding their nest, but it seems they will swarm at any disturbance to the slab they're nesting under. Since I use that step most days, they must be newly nesting under there.

I can't have the ants swarming at me whenever I use my garden steps or sit outside, and I also don't want them biting my cats, who also live to sit on that step. I'm not keen on trying to kill them, since they are outside and it also seems a bit pointless given that other ants would no doubt move in pretty quickly. I plan to lift the slab later to force them to leave the area, but what can I do to stop them (or others) from coming back to that area?

Thanks for any help.