Sociality is entwined as a life-history variable.
Social living poses challenges for individual fitness because of the increased risk of disease transmission among conspecifics. Despite this challenge, sociality is an evolutionarily successful lifestyle, occurring in the most abundant and diverse group of organisms on Earth – the social insects. ~ Columbian entomologist Margarita López-Uribe et al
Given the greater risk of disease among gregarious animals, one might think that sociality and a more robust immune system go hand in hand. Instead, the opposite is true, at least in insects.
The more social insects are, the weaker their immune responses tend to be. Eusocial insects that live in large colonies have the most languid immune systems. This puts a premium on hygiene. Being truly colonial makes clean living easier for individuals as the benefits of shared labor are enjoyed by the whole group.
The behaviors we see in eusocial species – like grooming each other or bringing antifungal materials into nests or hives – play an important role in colony health. ~ Margarita López-Uribe