Crabion

In Pikmin: The Return of the Puffmin
The Crabion is a crab-like enemy that has a shell on him for protection. On the back of him there is no shell, so you want to hit him in the back. However, he will try to run away from you.

Olimar's Notes
Agh! I can't seem to catch this thing! I do see a way to attack his back... If only I could reach it!