There were adults and larvae of the three-lined potato beetle, on a great clump of deadly nightshade (Solanum dulcamara), which is in the potato family. It is a non-native plant but grows freely in natural areas. As far as I know, the beetle is a native species. It is in the Chrysomelid family of beetles, and like many beetles in that family, the larvae cover themselves with big lumps of feces, presumably to deter predators. That is what the black stuff is on the backs of the yellow larvae.