You learn to hitch a ride on other creatures, mostly fish. Grabbing on, and eating their dead skin is a convenient food source.

Some of you burrow further into the skin, eating your host slowly, others try to hang on near the mouth where there is often the opportunity to grab bits of food.

Eventually, one enterprising individual finds a way to combine these two behaviours, and climbs right inside its host’s mouth where it can’t be scraped off, and there is plenty of food. This becomes the normal behaviour for the entire species.

But as you grow, there isn’t that much room in a fish’s mouth. I wonder what you can do to make room?

You eat the host’s tongue.

Yes, that’s right, you eat the entire tongue, and then sit in the bottom of the host’s mouth, doing the tongue’s job, helping to swallow prey - and helping yourself to anything that takes your fancy first.

You are - deep breath - one of the strangest creatures around: a tongue-eating louse.