Badger Tracks

By Anita Carpenter

The Mourning Cloak

As spring slowly reawakens, I'm searching for the first butterfly of the year. On an unusually warm late winter day, a mourning cloak butterfly may temporarily leave its protected overwintering spot to bask in the few, fleeting hours of warmth. Then as the temperature drops, the individual retreats to its hiding spot. It is not until mid-April when these intriguing butterflies finally emerge to continue their life cycle.

Easy to identify, mourning cloaks, Nymphalis antiopa, are fairly large, 3-1/2 inch butterflies. Their rich-brown upper (dorsal) wings are bordered by an obvious creamy yellow band. A row of brilliant blue or violet dots, whose color depends on how light strikes them, highlights a black stripe lying inside the yellow band. The ventral or underside of the wings are striated a dark, gray black bordered by a dirty-looking creamy band. This cryptic coloration makes discovery difficult when the butterfly rests with wings closed on a tree trunk.

Mourning cloaks prefer sun-dappled woodland trails and clearings, but they may show up anywhere. After emerging in spring, a male chooses a territory and selects a favored site within his territory where he perches and waits, often basking with wings open. Unlike many butterflies, he does not patrol his territory. When a flying individual invades his territory, the male flies out to investigate. If it is a receptive female mourning cloak and the chemical clues are right, a courtship spiral flight may ensue. If the chemical clues are inappropriate, the two individuals may spiral but then separate and go their separate ways. The male returns to his favorite perch to await the next passing interloper.

After mating, the female lays her spherical yellow eggs in a tightly packed cluster on a small twig or branch of a host tree which could be various willows, poplars, and birches. This egg-laying strategy differs from that of most butterflies which deposit single eggs on their host plants.

After hatching, the young caterpillars remain together on the host plant and feed on leaves in a communal web. As the caterpillars mature, they eventually wander off on their own. The black caterpillars are easy to identify. Covered with many branched black spines and tiny white dots, they sport a row of dull red-orange spots along their backs.

A very distinctive feature is the bright red prolegs or feet. Each mature caterpillar forms a chrysalis with the adult butterfly emerging from late June into early July. Only one generation is produced each year.

Newly-emerged mourning cloaks soon become inactive and hide during summer in a behavior termed aestivation which is defined as a period of summer dormancy. They become active again from September into October, feeding and preparing to overwinter in protective sites including wood piles, woodpecker holes, old barns, etc.

If you can get a close-up view of a mourning cloak butterfly, count the number of legs. Insects have 6 legs, but only 4 legs are visible on mourning cloaks. Actually, mourning cloaks have six legs with the two forelegs (front legs) being much reduced and resembling little brushes. Several butterfly species in the family Nymphalidae possess reduced forelegs and are collectively known as the brush-footed butterflies or brushfoots. The reduced forelegs, which contain chemoreceptors, are used for tasting. Mourning cloaks feed on tree sap, fruit, mud, and sip nectar.

Mourning cloak butterflies are the longest-lived adult butterfly, living 10 months. Most adult butterflies are short-lived from a few days to a few weeks.

One of my concerns is the period when mourning cloak caterpillars are feeding. Here is a big cluster of caterpillars feeding on a tree in a web. The first response is often "we have to get rid of these caterpillars before they infect the tree". Yes, they may defoliate a few twigs, but their presence is for a short time, and they don't harm or infect the tree. Almost immediately, the tree responds with new leaf growth, and you will soon be unaware that the caterpillars were ever present. Remember, the caterpillars are easy to identify. Look for their red feet. We need to do everything we can to protect our native butterflies.

Apr-May-Jun Newsletter 2025