Use yellow pikmin. They are the ONLY ones that don't get killed by electricity. You should destroy the Water attack thing on Titan Dweevil first, for it has a very wide attack range, then the electricity, then poison, and finally, fire. Once you've destroyed the electricity attack, feel free to use any other color pikmin, but yellows fly the highest, therefore making Titan Dweevil easier to hit. I REALLY hope I helped any of you having trouble with Titan Dweevil.