THE altruism of ants knows no bounds. Not only do pharaoh ants lay trails of pheromones that lead their nest-mates to food – it now seems the considerate insects also put up chemical “no entry” signs in front of unfruitful foraging routes.
Elva Robinson and her colleagues at the University of Sheffield in the UK observed foraging pharaoh ants – Monomorium pharaonis, a pest in kitchens worldwide – and were struck by a mystery. “They seemed to know in advance of a junction in their foraging route that some routes were not worth bothering with,” she says. The ants tended to…
