The rolling foi has replaced it's ancestor the rusty-red foi. It has evolved a new form of locomotion and feeding. The rolling foi now turns itself inside out in the form of a ball, with its stomach on the outside and only one sensory organ showing. It will then, with the aid of the mucus it's stomach produces, roll along on the sand under the water. As it rolls it picks up food particles and it digests them. It has also grown larger in order to pick up more food. Along with the color that helps camoflage it from predators the nasty burning from it's stomach acids will burn the predator's mouths.