The tongue-eating louse is a charming little isopod that likes to burrow into a fish's gills, settle in its mouth, then suck the blood out of its tongue until it falls off so that it can replace the organ and dine on the mucus.
The non-native species doesn't wait for stationary hosts. It actively pursues them, scuttling over the ground to secure a blood meal.
Even when two-thirds of their bodies are composed of fungal spores, the host cicadas continue to attempt mating in a drugged-out stupor.
A mosquito-borne disease might be responsible for the Louisiana Purchase.
They're not uncommon in lakes and rivers.