From the Super Mario Wiki
Klambers are yellow, metallic enemies resembling Scuttlebugs that appear only in Super Mario Sunshine. They can be found in both Ricco Harbor and Pianta Village. Some Klambers release a Blue Coin after being defeated, while others may release a regular coin, or nothing at all. Klambers are never found walking on the ground, and are usually seen climbing cages or walls, either vertically, or upside-down. When Mario encounters a Klamber climbing on a cage, he can kick or Ground Pound the cage in order to defeat it. However, when a Klamber is found climbing on a solid wall, it can only be defeated by using Yoshi to spray it with juice or eat it. Spraying it with water from F.L.U.D.D. will briefly immobilize it, but will not defeat it altogether. Unlike Red Electro-Koopas, which can also be found vertically climbing cages, Klambers always knock Mario off the cage and not only in a few cases.