The fungus Myrmicinosporidium durum has been known as an ant pathogen for several decades but it has been seldom reported in the literature. Recently, eight new hosts, seven collected in the eastern United States, and one from the Dominican Republic, were identified. New hosts in the US include the red imported fire ant, Solenopsis invicta, the thief ant, Solenopsis carolinensis, the Florida harvester ant, Pogonomyrmex badius, Paratrechina vividula, Pheidole tysoni, Pheidole bicarinata, and Pyramica membranifera. A Camponotus sp. infected with M. durum was collected in the Dominican Republic. M. durum-infected ants appear darker than normal due to the mature dark brown fungal spores found in most ant body parts. Immature spores are clear to light brown. The prevalence of the fungal disease varies among different host populations (2 and 83% of collected ant ants), however the fungus was most common in S. carolinensis (12 and 83%) and on ants collected in late summer and fall. Together, the wide host range and geographic distribution of this fungal disease suggest that M. durum is probably more widely distributed in ant populations than previously reported. Ant researchers examining large samples may be able to identify diseased individuals from other locations and ant species.