The spreading menace
Argentine ants that have migrated abroad coexist peacefully and can form immense colonies, with one extending for 3,700 miles along the Mediterranean coast.
However, in Argentina they are more aggressive and live in colonies just 200 yards wide.
The ants, which are 3mm long and can give a painful bite, began colonising the world through coffee shipments.
By killing native ants, the Argentine invaders can have a widespread effect. In California, horned lizards are in decline because the native harvester ants they eat are being killed off.