The microsporidium acts sort of like a fungus, releasing tiny spores that the ants then breathe in. “The spore actually fires out a harpoon like structure,” Lebrun said.

Symptoms of a microsporidium infection vary by parasite and host species. Sometimes it’s fatal. Other times the effects are so subtle that you’d really have to be looking to notice them.

The microsporidium Thelohania solenopsae Knell, Allen & Hazard was the most common microorganism; it was present at 25% of the sites and 8% of the colonies. In some sites within the surveyed region, ...