  Can insects transmit information about a threat through a physical barrier
they cannot cross? While the emission and detection of alarm pheromones is the
universally accepted mechanism of panic communication, there are still open
questions about the specific pheromones and type of ant-to-ant contacts
involved in specific scenarios, and how relevant is the role of non-chemical
communication. Here we report experiments suggesting that panicked ants can
transmit danger information through a physical barrier to nestmates located in
a safe arena when danger is simulated by using insect repellent. As ants in the
safe arena get danger information from nestmates trapped in an area
contaminated with a chemical, they retreat from the barrier in average. Visual
clues and pure mutual antennation seem to play a minor role as mechanisms of
danger information transmission through the obstacle. A detailed quantification
of the ant behavior reveals that examination of the legs of ants in the danger
arena by nestmates in the safe one may be relevant for danger information
transmission.
