These butterflies have a life-span of 11 to 12 months, one of the most extensive life-spans for any butterfly. The mourning cloak butterfly is a large, unique butterfly, with special markings that do not match those of any other butterfly, making it easily distinguishable. It can have a wingspan up to four inches. The dorsal side of its wings are a dark maroon, or occasionally brown, with ragged pale-yellow edges. Bright, iridescent blue spots line the black demarcation between the maroon and the yellow. The ventral side of the wings has grey striations, with the same pale-yellow edges. They are a part of the Nymphalis family, called the brush-footed butterflies due to their hairy front legs. The species does not display any sexual dimorphism. The caterpillars have black bodies and a line of red dots running down the back, and dark red legs. The body is covered with black spines, white dots converging on the ends of all the spines. The mourning cloak caterpillars can grow to be up to two inches in length.
They can usually be found in hardwood forests, though they have been found in virtually all habitats.