I have seen a lot lately about ants (called ‘formigas’ in Portuguese) being a problem as they furiously dig holes and take food back into their nests, eating just about anything. There are more than 10,000 types of ants, and their diet includes sugary nectar, as well as dead insects, seeds, plants, and fungus. Ants also drink water, which they find in sources like dew.

Here in Portugal, we are blessed with a lesser number than that - phew, I hear you exclaim, but there are more than enough different types here thank you very much, and all of them are really ugly close-up, with faces only a mother could love.

Apparently, there are around 34 species roaming underground here and include the dreaded fire ants that will bite you, or rather sting you. Being very aggressive when their nests are disturbed, they will swarm on an intruder, anchor themselves by biting to hold the skin stable, and then sting repeatedly, injecting a toxin alkaloid venom called solenopsin.

Another species here is the Carpenter Ant usually found in forests, and get their name because they excavate wood in order to build their nests. Of all ant species they are one of the most problematic and can cause serious property damage to homes and other buildings.

Common or Pavement Ants are the ones we probably see the most. They have many queens and will nest under rocks or in pavements as they mine the sand and soil from under concrete slabs, patios, pavements and driveways. These ants are all one size and do possess a stinger, but generally a person is not stung easily unless they catch you when you rest an arm or leg over a nest, as in a lawn.

These ants will also forage into your home for food items and will feed anything sweet or greasy. Because these ants nest underground and have multiple queens, there have been problems with management. They like to nest in places that are dry and easy to tunnel through, and loose soil in outdoor containers is a prime target - if soil falls out of a dry pots’ drainage holes, it presents the perfect area for a colony to start building a nest.

The simplest way to prevent ants from nesting in potted plants is to keep the soil moist, and if the pot dries out completely, just soak in water, and let it drain.

While it’s normal to have ants in a garden, sometimes they can be a sign of bigger problems. Ants are attracted to the sweet sap that is expelled from plants when pests like aphids feed on them, so if you see ants in your garden beds or pots, you may want to follow them to see where they’re going.

Garden ants do not eat plant roots but will tunnel or build their nests in and around the roots because the soil is generally looser there. Most of the time, the ones crawling on the leaves are feeding on the sweet sap produced by other pest damage.

Here’s something interesting about ants too - the largest ant colony in the world has been discovered in southern Europe. From the Atlantic coast of Spain to Mediterranean Italy, invading Argentine Ants recognize and treat each other as if they were from the same nest, despite being unrelated. The European invaders formed an unusual supercolony, with workers moving freely between nests and gathering food for unrelated queens.

To test the size and theories, experts captured ants from 33 places across coastal southern Europe and performed behavioral and genetic tests. First, they put pairs of ants from different locations together and checked for signs of aggression, and ants from 30 locations across Europe showed no aggression towards each other (although they fought with ants from a splinter supercolony in eastern Spain).

Genetic studies of Argentine Ants suggest that cooperation arose by accident, when the introduced population passed through a genetic bottleneck, making them unable to recognise friend or foe. My mind boggles at the thought of being taken over by ants, or southern Europe collapsing into one huge nest!


Marilyn writes regularly for The Portugal News, and has lived in the Algarve for some years. A dog-lover, she has lived in Ireland, UK, Bermuda and the Isle of Man. 

Marilyn Sheridan