Waste management by ants: the enhancing role of larvae

A fungus infected environment does not alter the behaviour of foraging ants

“…Whether generalist entomopathogenic fungi such as Metarhizium actually act as a strong selective force on ant societies is another matter, for which the answer needs to be mitigated. As regards to foraging, several ant species have evolved efficient and non-specific behavioural strategies that limit nest contamination such as forgoing the retrieval of sporulating dead insects 48 , 51 or fastly discarding wastes 42 . On the other hand, we found that the contamination of the environment where foraging takes place does not influence the behaviour of ants.…”

“…To counter sanitary risks, insect societies rely on social immunity which encompasses adaptive cooperative defences against pathogens having evolved at the physiological, behavioural and organisational levels 37 . Social immunity is namely achieved through grooming 38 , use of antimicrobial substances on nest materials 39 , discarding of waste 40 – 42 , removal of dead nestmates 43 , 44 or self-exclusion of moribund workers 45 , 46 . A first line of defence against pathogens consists in the prevention of their entry inside the colony, notably by avoiding to retrieve contaminated food items.…”

Spatial distancing by fungus-exposed Myrmica ants is prompted by sickness rather than contagiousness

“…At the most, late distancing may appear to be a prophylactic strategy against a potential future contamination if the sporulating cadavers of infected individuals remain inside the nest. However, the death of infected workers inside the nest is unlikely to be a major threat for the colony since social insects are well-known for their efficiency at discarding wastes and nestmate cadavers within a few hours, so well before the onset of sporulation (Ugelvig et al 2010, Diez et al 2013, Qiu et al 2015, Diez et al 2015, Pereira et al 2020. Therefore, the late distancing of fungus-contaminated ants would have no ultimate effect on the inclusive fitness of the colony and would come at no cost for the diseased individuals.…”

The power of poop: Defecation behaviors and social hygiene in insects

“…In response to increased likelihood of contracting pathogens, a wide range of hygienic behaviors evolved, which are specific to social insects: “social immunity,” a set of behavioral adaptations enabling insects to collectively prevent infection, including waste removal, grooming, cannibalism, undertaking, and maintaining “latrines” outside of nests [ 1 , 8 ]. For instance, Myrmica rubra worker ants, despite an increased risk of exposure to pathogens, remove more waste upon detection of pathogenic fungal conidia on feces when brood are present [ 9 ].…”