Altruistic disease signalling in ant colonies

Sick individuals often conceal their disease status to group members, thereby preventing social exclusion or aggression. Here, we show that infected ant pupae, on the contrary, actively emit a chemical signal that triggers their own destruction by colony members. In our experiments, this altruistic disease-signalling was performed only by worker but not queen pupae, reflecting differences in their immune capabilities, as worker pupae suffered from extensive pathogen replication whereas queen pupae were able to restrain infection. Inducing others to sacrifice oneself, only if one’s own immunity fails, suggests a fine-tuned interplay between individual and social immunity, efficiently achieving whole-colony health.