Hydro Dweevil
Caustic Dweevil
Mandarahnia sulfurnid
The Caustic Dweevil is a kind of enemy in the Pikmin 2 game. This Dweevil picks up any treasure or enemy body it can find. Caustic means corrosive, and this may portend to the fact it releases water. It is a blue dweevil that when agitated by attacks, it well release a blast of water that will attempt to drown out your Pikmin. This suitably makes Blue Pikmin the best choice in battle. Also since Purple Pikmin can stun any small Dweevil, they will also work well.
How to Kill
Pikmin
Swarm it with blues. If you don't have Blue Pikmin, it's probably better to kill it with your captains. Purples also work as they have a hundred percent chance of stunning any small Dweevil.
Captains
Run up to it and attack it until you see it glowing, run away before it attacks, then run back when the acid stops and repeat the assault.