How do butterflies go to the bathroom?

Adult butterflies do not urinate or defecate (or "go to the bathroom").

The larval life stage - the caterpillar - does all of the eating, and caterpillars almost continually defecate. Interestingly, when there enough caterpillars eating in the same place, their defecation is audible. That is, you can hear the poop! When gypsy moths (Lymantria dispar) infest a forest, the defecation of the caterpillars sounds like rain.

Occasionally adult butterflies drink so much they must emit a fine liquid spray from the tip of their abdomen. This substance is not like urine; rather, it is almost pure water.