For the good of the colony, young ants emit a chemical signal that warns other ants that they are sick and should be killed.
Begging for death when you are sick is not just a human thing. Young ants infected with deadly pathogens release a chemical signal characteristic that leads the workers to destroy them for the greater good of the colony.
The discovery, reported in a new publication in Nature Communications, sheds new light on how ant societies operate as “superorganisms” highly integrated, where individual survival is secondary to the health of the collective.
Ant colonies are especially vulnerable to disease because of their dense, constantly interacting populations. “Anthills are the perfect place for occurrence of a disease outbreakbecause there are thousands of ants crawling over each other,” said Erika Dawson, a behavioral ecologist at the Austrian Institute of Science and Technology and lead author of the new study.
Adult worker ants mitigate this risk by leaving the nest alone. die alone when infected. But young ants — called pupae — are sealed inside protective cocoons and are unable to isolate themselves. Previous research has shown that fatally ill pupae undergo a chemical change that changes their odor, causing the workers to tear the cocoon, puncture the pupa’s body and release a toxic fluid. This poison disinfects the breeding chamber and kills both the pathogen and the infected pupa.
The new study sought to determine whether this chemical signal is an intentional cry of destruction or just a byproduct of infection. To test this hypothesis, scientists extracted odorous compounds from infected pupae of the black garden ant (Lasius neglectus) and applied them to healthy pupae. The workers attacked and destroyed the healthy pupae, confirming that the odor alone triggers the lethal responsesays .
The researchers then observed that the infected pupae released the odor only when the worker ants were nearby, providing strong evidence that the signal is produced deliberately. “Although it is a sacrifice, it is also in their interests, as it means that your genes will survive and will be passed on to the next generation,” Dawson explained.
However, not all members of the colony follow this self-destructive protocol. The queen’s pupae, when infected, do not emit the chemical signal. Initially, Dawson’s team questioned whether the queens were “cheating the system”. Instead, their experiments showed that queen pupae have significantly stronger immune defenses and they often manage to overcome infections without putting the colony at risk.
Still, some questions remain. Dawson hopes future research will explore whether queen pupae can signal doom only when death becomes inevitable.
