Ujadani are a miniature type of insect appearing in Pikmin 2. They are very small, relative to even Olimar, who himself is considered tiny. They are approximately 0.7mm tall. When killed in the game, they drop one of three liquids. Oddly, they drop about three times as much liquid as it seems their bodies can hold. They also spew poison, so it can be assumed that these bugs are drugs.
Ujadani are the only creature in the game to not be listed in the Piklopedia. Heck, some goddamn clover got in the book before these guys. This maximises their exposure, and thus, they are commonly requested by many to be the villain rep for Pikmin.