Alerted by the frass at my feet, I looked up into the maple tree branches over my head. It didn’t take me long to locate the source of the frass. Two green-striped mapleworms. Frass is caterpillar poop. If you enjoy finding caterpillars it’d be wise to keep an eye out for frass. If there’s frass on the ground, there’ll be a caterpillar, or a group of caterpillars, feeding above. Green-striped mapleworms are the caterpillars, or larvae, of rosy maple moths.Read more