Tongue-eating Louse (Cymothoa exigua) is not an insect, but rather a parasitic isopod (Family: Cymothoidae ) that lives inside the mouths of fish. Juveniles gets into a fishes mouth by way of its gills. They will stay on the gill until the mature. Mature females will then attach themselves the host tongue, while males attach to the gill arches beneath and behind the female. The females will then bites onto the host tongue, draining blood away from the fishes tongue until the tongue atrophies away from lack of oxygen. The female Tongue-eating Louse then attaches itself to the remaining tongue stub, replacing the fishes tongue with its own body. The fish uses the “parasitic tongue” the same way it would used its real tongue. The Tongue-eating louse will feed on the host’s blood and mucus. Tongue-eating Louse do exhibits sexual reproduction and will under go protandy, when males are presents without a female
The Colbert Report report on this.