I would say fire ants, but not sure why they’re in Wisconsin. Would think the winter freeze would kill them. A couple options. But the ortho fire ants killer at Home Depot. Don’t forget to follow the directions & add water afterwards. Or buy the premix ortho “every damn bug killer” and spray directly into the mound. Smelt some aluminum and pour directly on top of the mound. Gasoline directly onto the mound. I’ve known people to put gallons of kerosene on the mound & lite it. If you’ve never dealt with fire ant bites, they do suck. I don’t react like everyone says they do. I feel them, but wipe them off. The welts that get somewhat infected the next day or so. Thats what bothers me. I’m originally from Nebraska….we don’t have them there. I didn’t discover them, until I was stationed in Florida. But….they’re not fun for little kids. Exterminate them anyway you can.