Social Bees Use Alarm Pheromones To Mark Danger Zones

Social bees were found to use chemical signals to warn other bees of their own species about the presence of a nearby predator by a study published this week in the journal Animal Behaviour.

Researchers at the University of Tours in France and the Experimental Station of Arid Zones of Almeria (EEZA-CSIC) proved that social bees use pheromone signals to mark the flowers where they have been previously attacked.

"Evasive alarm pheromones provoke an escape response in insects that visit a particular flower and until now, we were not sure of the role that these pheromones played in social bees," lead author of the study Ana L. Llandres, from the University of Tours, explained to Scientific Information and News Service (SINC).

"Our results indicate that, unlike solitary bees, social bees use this type of alert system on flowers to warn their conspecifics of the presence of a nearby predator," she said.

The research team carried out an experiment with both solitary and social bees from different countries - Australia, China, Spain and Singapore - for their study. A predator attack was simulated by trapping the bees with pincers in some plants. They also used control plants where no predator attack took place.

While the solitary bees were observed to respond in the same manner both in the case of flowers attacked by predators and with control flowers where no attack happened, the social bees behaved differently when approaching the flowers. Researchers noticed that the probability of social bees landing on control flowers was higher as compared to a flower where a conspecific (bees of same species) has been recently attacked and they have left a warning, leading to the result that the probability of social bees rejecting the flowers is much higher if the flowers had been the crime scene of a predator attack in the past.

The scientists note that the new study supports the existing idea that sociability of bees is linked to the evolution of warning signals.