Planting of fungus onto hibernating workers of the fungus-growing ant Mycetosoritis clorindae (Attini, Formicidae)

Abstract

We describe a peculiar fungus-coating behavior of the attine ant Mycetosoritis clorindae, where workers plant fungal mycelium on hibernating nestmates. Hibernating nestmates become ultimately enveloped in a live mycelial coat, remain motionless in this coated state, and essentially become integrated into the garden matrix. The shallow nest architecture of M. clorindae (depth of main garden is 15-30 cm) in southern Brazil forces the ants to overwinter at relatively low temperatures in the topmost soil layer. Fungal coating may help the ants to survive the prolonged periods of immobility during winter. Fungus-planting on attine adults is so far unknown from other attine species, but the behavior parallels the planting of mycelium on larvae and pupae occurring in many attine species. Planting of mycelium on adult nestmates may have been overlooked so far in attine ants because this behavior may occur only in dormant nests, which are least frequently collected. The possible adaptive functions of fungus coatings of hibernating adults and developing brood are likely similar, including for example physical protection, prevention of desiccation, shielding against parasites and predators (e.g., army ants), or defense against diseases.