Amazing Ants

Ants find food using an amazing system.

They have no map. They can’t see or smell beyond a few centimeters. So, how do ants find your picnic basket every time? And so quickly? And, after one ant finds your picnic basket, how does the entire colony soon show up too?

This activity uses scented ropes to mimic the pheromone trail of ants. For the scented ropes activity you will need 2-3 pieces of 1-1.5 m long hemp or cotton rope, saturated with a strong-smelling essential oil (e.g. peppermint). Place the ropes in a plastic box, add a few drops of essential oil, replace and lid and leave for the oil to impregnate the rope.

Ask 2-3 pupils (according to the number of ropes) to be 'ants'. Blindfold their eyes. Put the ropes on the ground in a non-straight pattern, but not too 'curvy'. Then, guide the students to their knees and 'show' their noses to one end of a rope. Their task is to move along the rope using the scent, without seeing or touching the rope.

You may want to put a bunched-up cloth or T-shirt in the students’ hands, so they can’t accidentally feel the rope. You can also cross the ropes to make the task more challenging.

Simple explanation

If you lose your friends in the woods, sometimes you can still find them by paying attention to the clues they leave behind. To find your friends when there are two paths in the grass, for example, you choose the path that is more trampled. It’s similar with ants, they just use another sense. Scientists have found that ants emit a scent (called pheromone), which helps the others know where different ants have travelled.

More detailed explanation

When ants leave the nest to find food, they walk around randomly, but always leaving a pheromone scent behind them. If an ant bumps into food, it takes a piece, and follows its own pheromone trail back to the nest. So now this pheromone trail is twice as strong as any of the other pheromone trails on the ground. The ants have a simple rule, which is, if you bump into a pheromone trail that is stronger than yours, follow it. This is how the entire ant colony eventually discovers the way to your picnic basket, without a map, and without a leader. 

The story from above can be translated to ant language of simple rules like this:

Look at the four images above. Four scout ants start to find food and leave pheromone on their way.

• Image 1: Ant A finds food and goes back on the same track, doubling the strength of the pheromone trail.
• Image 2: Ant D finds the double strong trail and follows it.
• Image 3: Ant C also finds the main track.
• Image 4: Ant B finds the food from the other direction and starts a new track to it.

As we saw, ants find food by following the strongest pheromone trail. The strongest trail is the one that an ant just used twice (once from the nest to food, second from the food back to the nest). The other trails evaporate slowly.

In the world of the internet we can find similar methods. The number of hyperlinks is like the strength of the pheromone trails. As the number of hyperlinks goes up, the chance that people will go to that webpage goes up. Similarly, as the strength of a pheromone trail goes up, the likelihood that an ant will follow it goes up.

Think about the number of 'likes' a page has – you will choose a gadget, item of clothing or a holiday destination if you find more likes.

Some companies today (e.g. Air Liquide) use computer programs inspired by ants to find shorter routes for making deliveries.

Some STEAM opportunities include:

• Observing and raising questions about how different animals adapt.
• Analyse advantage and disadvantage of different adaptations/behaviours.
• Understand the use of sequence , selection and repetition in programs.
• Use logical reasoning to explain how simple algorithms work.

Learn more about how ant forage for food (find out more).