Ants 'Use Math' to Find Fastest Route

Tanya Lewis, LiveScience Staff Writer

Date: 17 April 2013 Time: 01:54 PM ET

Just as light does, ants traveling through different materials follow the fastest path, not the shortest one.

A recent study found that when fire ants (Wasmannia auropunctata) crossed different surfaces, the insects chose the route that would minimize their total walking time, rather than the distance traveled. The ants' behavior offers a window into how groups of social insects self-organize, the scientists say.

In optics, a ray of light traveling between two points takes the path that requires the least amount of time, even if it's not the shortest distance — which is known as "Fermat's principle of least time." For example, imagine a lifeguard rushing to save someone in the ocean some distance down the beach. The quickest way for her to get to the victim would be to run along the beach first, in order to minimize the time she would have to spend swimming, which usually takes longer than running.

In the study, researchers collected colonies of the little fire ant — one of the world's 100 most invasive species — at sites in Israel. Each colony contained a few thousand worker ants and several queens. The ants were placed in a corner of an enclosure, and cockroaches were provided as a food source in the opposite corner. To get to the cockroaches, the ants had to cross a foraging area covered with different materials: smooth felt, rough felt or a glassy surface. The scientists tested the ants on surfaces composed of pairs of these materials next to each other (glass and rough felt, glass and smooth felt, smooth felt and rough felt).

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