Found on a garden site:


Whilst ants are not a pest and do some benefit in the garden. Most
people do not like a ant setting up house under their patio or in
their lawn.
A sure fire way to get rid of them is mix a small bottle of clove oil
(from the chemist) in a large watering can with a rose sprinkler.
Quickly water this over the area the ants have set up home ........
and stand back! First you will see the flying ants leaving the nest in
droves, the soldier ants will follow them on foot. Tried tested and
never failed.
Ian, Newcastle