A very large Catocala with a correspondingly very large larva. Overall habitus like a rumpled amatrix, body color light gray with varying broken dorsal, lateral, subventral lines; A5 with bulbous light-topped projection, modestly delineated patch, A8 inflated; venter whitish with black spotting throughout; lateral filaments lush and long; head capsule with broad and crisply delimited black bands on side, tapering toward ocelli, extending up to but not strongly connecting on top, lobe faces light gray with indistinct striping. Wild larvae have not been taken in the field, but marmorata adults are associated with hardwood swamp habitats containing only Swamp Cottonwood (Populus heterophylla) in Indiana and Delaware. The distribution of heterophylla is split, with populations centered on the Missisippi drainage and then along the east coast and piedmont from North Carolina to New Jersey (with outlying isolated disjunct populations reaching Michigan and Connecticut). This tree is not present in the Appalachians where marmorata also occurs, which suggests an additional foodplant.