We recognise dead people by the absence of signals that indicate life - movement, responsiveness, pulses, brain activity, and so on. The Argentine ant does the same, but its signal is a chemical one. Throughout its life, an ant uses chemicals in its skin to automatically send out a message to its nest-mates, saying "I'm alive. Don't throw me out." When it dies, these "chemicals of life" fade away, and their bodies are evicted.
Social insects like ants and honeybees are fastidious about their colony's tidiness. If any individuals die, they're quickly removed and thrown away in one of the nest's refuse tips. This behaviour is known as necrophoresis (literally "moving the dead") and it protects the remaining colony from any parasites or diseases that may have killed their former colleague.
Scientists have long believed that ants and bees recognise dead individuals by smelling chemicals like fatty acids that are ...
