Bold claim: sick ant pupae sacrifice themselves to protect the colony, revealing a striking form of collective defense. But here’s where it gets controversial: is this truly an intentional, coordinated signal, or could it be a byproduct of infection that’s been misread as purposeful altruism?
A new study in Nature Communications examines this question using the ant species Lasius neglectus and the fungal pathogen Metarhizium brunneum. Researchers infected sick worker pupae — the developmental stage between larvae and adults encased in cocoons — and observed their interactions both when alone and within groups. The key discovery is that these ill pupae emit a distinct chemical cue, a modified body odor, which prompts adult nestmates to destroy them. Crucially, this signal only appeared when sick pupae were in the presence of adult workers, suggesting the cue is not merely a passive byproduct of infection or immune activity, but an active trigger produced in social context.
To test the signal’s role, the team applied the chemical cue to healthy pupae. The result was clear: adult workers attacked and destroyed the treated pupae, confirming that the chemical functions as a signal that induces self-sacrificial removal for the colony’s sake.
This behavior is framed as altruism at the colony level, where sick individuals contribute to the health of the group by limiting disease spread. In effect, the ants appear to operate as a superorganism, coordinating individual actions to protect the collective, much like an immune response on a communal scale.
Publication details:
- Dawson, E.H.; Hoenigsberger, M.; Kampleitner, N.; et al. Altruistic disease signalling in ant colonies. Nature Communications, 16:10511 (2025).
- Open access available. Publication date: 02 December 2025.
For further reading, see the article: https://doi.org/10.1038/s41467-025-66175-z
Discussion prompts: Do you find this interpretation of a deliberate social signal more convincing than the idea of a byproduct being repurposed by the colony? What implications might this have for our understanding of social immunity in other species? How might environmental factors influence the reliability or evolution of such signals in ant colonies?
