Ants leave 'road signs' for others: study
Ants scouting for food place a tiny scent marker on branches that do
not lead to a reward, according to a study published in Nature, the
weekly British science weekly.

The pheromone acts like a "no-entry signal" to other ants, telling
them not to waste their time going down that route, it says.

The discovery was made by animal scientists at Britain's University
of Sheffield.

In a lab, they got a scouting colony of pharaoh ants (Monomorium
pharaonis) to explore branches that led to no reward. Paper covers
were placed at the branch's forks.

The paper covers were then taken off and transferred to another set
of branches. This set had already been explored by another ant
colony, which found a tasty meal of sucrose at the end of the trail.

Even though the food reward was still there, ants performed a U-turn
or chose another direction whenever they came across the covers.

The team concludes that the ants use a repellent pheromone to mark
unrewarding branches at "decision-points" - where branches fork.

"It provides advance warning, like human road signs situated before
junctions," the authors suggest.

In a study published last December, the same team found that pharaoh
ants deposited pheromones wherever the trail forked at 60 degrees.
The markers are like invisible signposts, helping ants to find their
way home.

The latest finding amplifies this, showing that the ants also use
scent as a negative signal to help them in their quest for food.

-AFP