Mourning Cloak Butterfly

The Mourning Cloak is a large brushfoot butterfly (family Nymphalidae) named for its somber, cloak-like coloring reminiscent of old mourning garments. It is one of the longest-lived butterfly species as an adult, with individuals surviving nearly a year through hibernation.

It holds special notability among lepidopterists because it is often the very first butterfly seen in spring, sometimes emerging from winter shelter while snow still lingers, since it overwinters as a fully formed adult rather than as an egg, larva, or pupa. This unusual life-history trait sets it apart from most temperate butterflies.

Ecologically it fits into deciduous woodland and riparian communities, where its caterpillars feed communally on tree foliage and the adults contribute to pollination of early tree sap flows and spring flowers, while also serving as prey for birds.

• Wings are dark maroon-brown to almost black with a ragged cream-yellow border along the outer edge.
• A row of iridescent blue-violet spots runs just inside the yellow border on both fore- and hindwings.
• Wing margins are distinctly scalloped and jagged rather than smooth, aiding camouflage as dead leaves when wings are closed.
• Underside is dark, bark-like gray-brown, providing excellent camouflage at rest on tree trunks; no common close lookalike in most of its range.

Widespread across North America, Europe, and temperate Asia, favoring deciduous and mixed woodlands, forest edges, parks, and streamside corridors where host trees grow. Adults are active from very early spring through fall, and uniquely overwinter as adults tucked into bark crevices, woodpiles, or tree cavities, emerging on warm winter days.

Adults are strong, gliding fliers often seen basking on tree trunks or bare ground with wings spread to absorb sunlight. Rather than favoring flower nectar, adults frequently feed on tree sap, rotting fruit, and mud, and are known to be highly territorial, chasing off other butterflies and even small birds from favored perches. Caterpillars feed gregariously in silk webbing on willow, elm, poplar, and birch foliage, stripping branches before dispersing to pupate individually.

Eggs are laid in clusters encircling twigs of host trees; the resulting caterpillars are spiny, black with red-orange spots, and feed communally through several instars before wandering off alone to pupate. Pupation occurs in a gray-brown angular chrysalis hung from a twig or structure, with adults emerging in early to mid-summer. There is typically one generation per year in northern areas and up to two further south, and the summer-emerged adults enter a dormant state and overwinter as adults to re-emerge the following spring.