The red imported fire ant is an invasive species that lives in the Southern US, among other places. Here in Louisiana we face a constant battle with the damned little ants, striving mightily to keep them out of our yards, pastures and woodlands. You can't completely eradicate them, but you can make them pay the price for setting up their house on your land.
As a bullet caster, I'd sometimes have an alloy that wouldn't act right, had too much trash in it, or for some reason was unsuitable for bullet casting. When I'd get an alloy I couldn't use, I'd sometimes pour it down a convenient ant hill. We'd let it cool, then dig it up, wash the dirt out of it, and the kids could see the intricate little tunnels that the ants dug. The kids learned from the exercise and I eradicated one ant hill. Win, win.
It seems some guy is doing this with aluminum, which is still cool.
All the usual disclaimers apply. Don't try this at home, molten metal is hot, your mileage might vary. Don't pour molten metal into your boots, keep away from children, etc.