Butterfly poop is commonly referred to as “frass.”

Frass is the excrement or waste produced by insects, including butterflies, as a result of their digestion process. It typically consists of digested plant matter and is often seen in the form of small, dry pellets or droplets. For Monarch Butterflies, the only plant matter they will digest is Milkweed!

Frass can sometimes be found near feeding or resting areas of butterflies, and its presence can indicate their activity in the vicinity.