War on ants
This is what I've done with succes over the years a couple of times with very persistent nests and when all other measures didn't work
1. Locate the nest and as many exits as you can find, by backtrailing any ants you see.
2. Buy flammable liquid that burns long and well (a gallon of BBQ ignition fluid should do it)
3. Wearing long sleeves and gloves; close off as many exits as you can find with plain packed earth, except the largest one you can find
4. Poke the remaining exit and open it up wide with a stick until ants start to congregate in numbers
5. Pour liquid down the exit, all of it in a steady pour, now wait 20 seconds so it soaks the nest and reaches the main chamber
6. Stand clear and light the liquid, then move away as you'll find the earth gets hot around the nest area.
The ants will either all burn, cook or move away.. so far it hasn't failed me..
Of course this only works on ants nests that are not inside a building