Ants’ Chemical Stop Sign
Foraging ants have evolved a clever ‘stop sign’ to inform their nestmates of unrewarding paths according to a Brief Communication in the 11 24 05 Nature. Researchers have long known that ants communicate by way of attractive trail pheromones, leading their fellow ants to food or water. But this research shows that they use opposing signals to warn of barren trails.
Elva J. H. Robinson and colleagues show that Pharaoh’s ants (Monomorium pharaonis) use a system that includes negative, repellent pheromones with signals concentrated at decision points —where trails fork. Exactly how this encourages foraging efficiency is not known. The authors argue that negative pheromones may complement positive ones or could help ants to escape from an unnecessarily long route to food that is being reinforced by attractive signals.
