A ferocious little European invader has established a beach-head in eastern Canada and shows signs of spreading across the country. The European fire ant is only five millimetres long, but is aggressive and can deliver a painful sting that leaves welts that last for days.

The ants will swarm invaders in their areas, even humans and pets. In rural Nova Scotia, colonies appear to have exploded in recent years, expanding their range and worrying entomologists.

Learn about ants at our pests page or read the full story.