Paris. Young sick ants emit a smell that urges adult specimens to kill them to protect the colony from any epidemic, according to a study published yesterday, which also explains that the queens seem to avoid this act of sacrifice.

Anthills are “perfect terrain for an epidemic to spread with thousands of ants crawling over each other,” Erika Dawson, behavioral ecologist at the Austrian Institute of Science and Technology and lead author of this study published in Nature Communications.

When adults contract a disease that could spread, they leave the nest to die alone. But the young ants, in the state known as pupae, are still in their cocoon and cannot distance themselves.

Scientists already knew that when these chrysalises are in the terminal stage of a disease, a chemical change occurs that generates an odor.

The adults gather around them, remove the cocoon and “make holes in the chrysalises to spread a poison,” says Dawson, which acts as a disinfectant, killing both the pathogen and the chrysalis.

With this study we wanted to determine if young ants had an active role in this process, emitting a message like “hey! come and kill me,” adds the researcher.

First, they isolated the odor emitted by a diseased chrysalis of the black garden ant family (Lasius neglectus) and introduced it into a healthy laboratory offspring: the worker ants came to destroy it.

The scientists later demonstrated that the sick chrysalises only produced that smell in the presence of adult ants, as if it were an “altruistic” sacrifice, according to the study.

The investigations also showed that this self-destructive initiative did not apply to queens in the chrysalis state. If they are sick, they do not tell the community.

“We discovered that queens in the chrysalis state have a much better immune system than workers. Therefore, they are capable of fighting infection and we believe that is the reason why they are not identified,” explains the researcher.