Caustic Dweevil

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.

Olimar's Notes
The Caustic Dweevil is one member of an insect family known for mimicking objects by carrying them on their backs. Several points of differentiation with other members of the species have been confirmed, such as body color and behavioral patterns, but none of these suggest major deviations in the creature's genetic structure. This makes it clear that it is a relative of the family. When attacked by enemies, the Caustic Dweevil spits out bodily fluids in response. Space suits corrode and oxidize when they come into contact with this highly acidic liquid.

Louie's Notes
Inedible. Effects of consumption include uncontrollable arm flailing and enthusiastic dishwashing.

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 waterworks stop (You don't have protection from this attack) and repeat the assault.

Pikmin:Redemption
These can be found above ground and when carring the corpse of a Soapy Dweevil the attack power and speed of the dweevil increase.