Editor’s note: This is our first guest blogger post for the Insectes Sociaux blog where our blogger chooses an IS article to write about. Previously, bloggers have written about their own research. I hope you enjoy it.

A blog post highlighting the article written by A.A. Yates and P. Nonacs in Insectes Sociaux

Written by Ravindra Palavalli Nettimi

You are hungry. So you order a pizza. *Yummy, yummy, yummy*

But the delivery person is new to the city. What if he or she could use software to find the shortest path with the fewest turns to get you your yummy pizza as fast as possible? Ants could come to your rescue here!

The pizza delivery problem: how to get to the destination in the most efficient way possible? Illustration: R. Palavalli Nettimi

Many ants face similar maze-like challenge when foraging for honeydew secreted by scale insects in trees. In a recent study published in Insectes Sociaux, A. A. Yates and P. Nonacs from the University of California discovered that ants in a maze take straight line paths with the fewest turns.

To test whether ants can collectively find the shortest paths with the fewest turns, they attached a colony of Linepithema humile ants to a maze consisting of plastic cups connected by plastic tubes and kept some food (mmm… cheese!) in one of the cups as shown below.

A representation of the experimental array used in the study. Illustration: R. Palavalli Nettimi

Initially, the ants explored all the routes equally and laid pheromone trails as they went. The shortest paths to the food ended up getting more pheromone trails since more ants were likely to have found food sooner than the ants exploring longer paths. (In this case, there are three possible shortest paths, two of them are shown in colour). Each ant laid pheromones and also followed the pheromones trails laid by other ants, creating a positive feedback system leading to the shortest paths getting the most pheromone trails.

This phenomenon is known as the travelling salesman problem. The simple rules that the ants use to find the paths have been coded in software used by companies to find out the optimal paths (shortest distances) to deliver milk across many cities or suburbs.

But often finding the shortest path is not enough. The shortest path could involve more turns and thus a higher chance of getting lost. Or the shortest path could have a traffic jam and lead to reduced speed.

Can the ants come to our rescue again?

The researchers showed that the ants prefer the shortest paths (with fewest turns) when exploring to find the cheese. In the figure above, the green path has two turns, while the orange path has one turn to reach the food. The ants were more likely to follow the orange path than the green one. A path with fewer turns can decrease the chance of foragers getting lost. More turns in the path can make it difficult to learn the path and increase the chances of getting lost and wasting foraging time.

It is likely that the preference for the fewest turns could be a consequence of the ‘wall-following’ tendencies of the ants.

Perhaps all of the rules used by ants could be incorporated into the software to not just find the shortest path, but the most efficient path with fewest turns, or highest speed.

Has your pizza been delivered yet?

About the author:
Ravindra Palavalli Nettimi is a PhD student at Macquarie University in Sydney. He writes a blog (https://antists.wordpress.com) and hosts a podcast called Just-questions (https://soundcloud.com/user-951555253 ). Learn more from his website: http://rvndrpn.wixsite.com/ravindra