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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

August 2000

The mourning cloak butterfly. © Rick Cech
While it waits for a mate, a mourning cloak butterfly will bask with wings open in a sunny spot.

© Rick Cech

A chance encounter

Cloaked in chocolate brown, this butterfly pitches woo on a woodland path.

Anita Carpenter

Have you ever walked along a sun-dappled woodland trail and had a mourning cloak butterfly (Nymphalis antiopa) flit about your face? Did you brush it aside as a nuisance insect and continue on your way? You should have stopped and enjoyed the moment, for the lovesick male was courting you as a potential mate. He approached because you entered his territory. When you didn't respond to his advances, he dismissed you as unacceptable and returned to his favorite perch. Undaunted, he'll wait for the next passer-by, perhaps a wandering female mourning cloak, and approach again.

The mourning cloak is found in woods and open areas throughout Wisconsin, and it is unmistakable. The butterfly's four-inch wingspan is robed in rich chocolate brown, edged by a creamy yellow margin. A row of iridescent violet to blue dots highlights a black band lying within the creamy border. The underside of the wing is dark gray to black bordered by a dirty looking cream-colored band. This cryptic coloration truly cloaks the butterfly when it rests with its wings closed on a tree trunk. Both sexes are similarly colored.

In the warmth of summer, love is in the air for the mourning cloak. Males establish territories. Within their turf, a favored branch or leaf serves as a perch to wait for females that wander through. During days of waiting, mourning cloaks often bask with their wings open in a sunny spot on the path or on a sunbeam striking a leaf. If you flush a basking mourning cloak, it will float along the trail drifting lazily back and forth, up and down before returning to its chosen sunny spot.

After a receptive female enters his territory and mates, the female searches for willows on which to lay her eggs. American elm, white birch, aspen or hackberry trees are sometimes suitable substitutes. Most butterflies lay single eggs on separate plants, but mourning cloaks lay up to 250 round yellow eggs in a tight, one-layered cluster around a twig. Once eggs are laid, the adults die. Within a few days, the eggs hatch and tiny caterpillars begin to eat, grow and molt. Boy do they eat! With so many ravenous larvae in one area, they often defoliate the shrub or tree branch. Don't be alarmed. The tree survives and responds by sending out new growth after the caterpillars leave.

A mourning cloak larva, recognizable by its bright red prolegs. 'Red on black' coloring often occurs in nature as a
warning of poisonins animals and plants. © John Baker
A mourning cloak larva, recognizable by its bright red prolegs. "Red on black" coloring often occurs in nature as a warning of poisonins animals and plants.

© John Baker

The black larvae are decorated with branched black spines. They have four pairs of bright red prolegs. If disturbed, the caterpillars twitch and wave their bodies sinuously to ward off would-be predators.

After feeding and reaching mature size, the two-inch spiny larvae find safe places to pupate and transform into adult butterflies. Newly-emerged adults are easy to recognize as their wings are whole, brightly colored and unblemished. The mourning cloaks are North America's longest-lived adult butterflies, often surviving ten months because the adults have it pretty easy. They bask, rest and feed, storing up energy for winter hibernation. You can see mourning cloaks well into autumn before they seek shelter under tree bark, in cavities or in old open buildings where they can escape winter's icy blasts.

Even in winter, don't be surprised to see a mourning cloak floating about, fooled into thinking it's spring by a warm day. As late afternoon temperatures retreat below the freezing mark, the butterfly ends its brief winter emergence and returns to a hiding spot until warmer weather prevails. Then the cycle will start again as territorial males and wandering females meet in a chance encounter on a wooded trail.

Anita Carpenter trods the wooded paths near her Oshkosh home.