Tridentbite

A Tridentbite is an arthropoid creature resembling a trilobite. Its head is triple-pronged, and it has a long, slender body. Tridentbites charge at pikmin, tearing through them with its head. This causes instant death to pikmin that are hit directly, and not even Rock Pikmin are immune to this attack. Fortunately, they can be knocked over if enough damage is done to their heads. While knocked over, their defense becomes lower, and they now can be swarmed for a quick defeat.

How to Kill
Tridentbites can be killed by tossing a number of pikmin atop their heads. The best choice of pikmin would be either Purple Pikmin or Rock Pikmin. After they are knocked onto their backs, they can be swarmed.