Workers of the red imported fire ant, Solenopsis invicta, and the Florida harvester ant, Pogonomyrmex badius, are naturally infected in Florida with a yeast-like fungus visible through the cuticle. Ants show no behavior change when infected by the fungus, and no signs of the disease other then the fungal cells observed under high magnification. When inoculated on S. invicta larvae and pupae, the pathogen causes premature mortality of the ants either in the immature or adult stages. Inoculation with lower doses allows infected ants to survive and emerge as infected adults. This fungus has been cultured in vitro yielding a filamentous fungus that produces thin, delicate, light beige synnemata on which conidia are formed in chains. Similar growth can be observed on infected ant cadavers placed under moist conditions. The fungus has been tentatively classified as Akanthomyces sp., and may be related to a fungus described as Insecticola clavata.