Researchers have discovered that terminally ill ant pupae release a distinctive scent to alert their colony, prompting workers to disinfect them and prevent infection spread. This altruistic behavior sacrifices the individual but safeguards the superorganism-like colony. The findings highlight parallels between ant societies and multicellular organisms.
Ant colonies function as superorganisms, with individuals cooperating like cells in a body. A study from the Institute of Science and Technology Austria (ISTA) reveals how fatally infected pupae contribute to this unity by emitting a chemical alarm when their infections are incurable.
When worker pupae face deadly pathogens, they produce a non-volatile scent on their body surface, altering their natural odor profile. Two specific components intensify, signaling danger without diffusing broadly through the nest. This cue draws worker ants, who swiftly open the pupa's cocoon, make incisions, and apply formic acid—a natural antimicrobial—to eliminate the threat. The process kills the pupa but halts the infection's progression, protecting the colony's long-term survival.
"What appears to be self-sacrifice at first glance is, in fact, also beneficial to the signaler: it safeguards its nestmates, with whom it shares many genes," said Erika Dawson, the study's first author and former postdoc in Sylvia Cremer's Social Immunity group at ISTA. By alerting the colony early, the pupa indirectly aids the propagation of its genes through healthy relatives.
Experiments confirmed the scent's role: researchers transferred the altered odor to healthy pupae, triggering the same disinfection response from workers. Notably, queen pupae, with stronger immune defenses, do not emit this signal, ensuring responses target only genuine threats. Adult ants, by contrast, self-isolate or leave the nest when ill, but immobile pupae rely on this external aid.
"The signal must be both sensitive and specific," Cremer noted, emphasizing its precision in avoiding unnecessary interventions. Conducted with chemical ecologist Thomas Schmitt from the University of Würzburg, the research documents this altruistic disease signaling for the first time in social insects. Published in Nature Communications on December 3, 2025, the study underscores the evolutionary sophistication of ant immunity.