Austria – Researchers at the Institute of Science and Technology Austria (ISTA) have uncovered a striking form of altruistic self-sacrifice in ant colonies, revealing that terminally ill ant brood emit a chemical warning signal that alerts workers to their deadly infection.

Ant colonies function as tightly coordinated “superorganisms,” with each individual acting like a cell in a larger body. In this system, dying brood take the opposite approach of many social animals: instead of hiding illness, they actively release an odor announcing their incurable condition and the risk they pose.

Upon detecting this signal, worker ants immediately unpack the sick pupae from their cocoons, create small openings in their body surface, and apply formic acid—their antimicrobial poison—to disinfect them. This treatment kills both the multiplying pathogens and the pupa itself.

“What appears to be self-sacrifice at first glance is, in fact, also beneficial to the signaler,” explains Erika Dawson, first author of the study. By warning the colony, these ants protect closely related nestmates and help ensure the colony’s survival and future reproduction.

In collaboration with chemical ecologist Thomas Schmitt of the University of Würzburg, the team showed that infected pupae signal through changes in their scent profile. Two odor components on the body surface intensify when a pupa is fatally ill. When researchers transferred this scent to healthy brood, workers immediately began unpacking them, proving the odor change alone triggers the response.

The signal is used only when infection becomes uncontrollable. Queen pupae, with stronger immune defenses, do not emit it; worker brood unable to stop infection do. This precision prevents unnecessary sacrifice and allows the colony to react only to genuine threats.

Ants and body cells share this strategy: immobile brood and infected cells both rely on “find-me and eat-me” signals to attract helpers who remove them before they endanger the whole system.

The study, published in Nature Communications, highlights how cooperation and self-sacrifice maintain the health of complex biological systems, from organisms to superorganisms.

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