Abstract

Social insects fight disease together. They are protected against disease not only by their individual immunity, but also their collective and cooperative hygiene and sanitary care, providing social immunity to the colony. These colony-level disease defences show an amazingly similar organisation to the immune system of individual organisms. This is because insect colonies form “superorganisms”, where the individual insects – just like cells within a body – specialise on either reproduction (the queen resp. germline) or maintenance (the sterile workers resp. soma). The fitness of each individual is therefore strictly connected to the overall fitness of the colony, promoting unconditional cooperation between colony members. This resulted in the evolution of highly sophisticated colony disease defences, including hygienic suicide by social apoptosis and altruistic ‘find me and eat me’ signalling of infected individuals.