Acid Beetle

The Acidic Beetle is an enemy that was first introduced in the game Pikmin:The After Years. Unlike Anode Beetles, they have green spots and spray acid when two of them meet. This attack will asphyxiate all but Green Pikmin.

How to Kill
Throwing a Green Pikmin on top if it will flip it over and because they are immune to acid, they won't asphyxiate. A Purple Pikmin will also flip multiple of these beasts over due to the shock-waves they create, but take great caution.

-- Gamefreak75