Abstract: Previous studies have focused on how ants deal with workers infected by pathogens but how pupae are protected from infection by fungi is not well understood. The behavioral mechanisms adopted by Solenopsis invicta (red imported fire ants, RIFA) adult workers to protect pupae against Metarhizium anisopliae infection were studied. We observed the behavioral changes of M. anisopliae infected adult workers in the brood chamber as well as the behavioral changes of healthy workers to fungus exposed pupae. The time of fungus infected workers spent in the pupal chamber reduced significantly from 103.4 s on the first day to 38.5 s on the third day. Moreover, the percentage of time spending on brood care in the pupal chamber reduced significantly from 13.6% on the first day to 3.5% on the third day. When pupae were infected by M. anisopliae, workers performed 5.3 times more grooming to fungus exposed pupae than controls, and the duration of each grooming bout to fungus exposed pupae was 5.2 times longer than controls. Grooming did remove many conidia on the surface of fungus exposed pupae. The mean numbers of conidia on the surface of pupae were 103.1, 51.6 and 31.3 when no workers, two workers and ten workers accompanied a pupa, respectively. The presence of workers resulted in a lower germination rate of conidia on the surface of pupae. The mean germination rates of conidia after 20 h of inoculation on the surface of pupae were 95.1%, 80.4% and 59.9%, in the treatments with no worker, two workers and ten workers respectively. There was a positive correlation between the emergence rate of pupae and the number of accompanying workers. RIFA protect their pupae from infection by M. anisopliae through social behaviors which enable the sustainable development of their population.