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Door to Nature: A Winter Butterfly

Years ago we received a lovely “troll” postcard from a dear Chicago area Swedish friend who was traveling in her homeland. What immediately caught our eye was the beautiful, colored butterfly stamp featuring what to the Swedes is the “Sorgmantel.”

In small print below the butterfly on the stamp is its scientific name, Nymphalic antropa, the international name used by scientists in all countries where this large butterfly lives. We in the U.S. call it the mourning cloak.

The wings and bodies of these three-inch wide creatures are deep purplish-brown, velvety and, in fact, quite hairy. Even the surfaces of their eyes are covered by fine hairs. A broad yellow band on the outer margins of their wings is highlighted by a row of light blue spots as seen from above, just inside the band. Two white spots adorn the outer edge of each forewing.

Describe this butterfly to someone from England and the response may be: “Oh, do you mean the Camberwell Beauty?” The first mourning cloak butterflies caught in England were thought to have traveled there as adults on barges carrying wooden posts from Finland.

The Milbert’s tortoiseshell is another species of butterfly that can overwinter as an adult. Photo by Roy Lukes.

They were captured in 1748 in the rustic country village of Camberwell on the outskirts of London and given the name Camberwell beauty. Today, Camberwell has lost its country charm and instead has been incorporated into the borough of Southwark, a bustling metropolitan borough of south London.

The mourning cloak was the last butterfly we saw on our property last year, that being on a sunny November day. What continually amazes us is that this very butterfly is in all likelihood spending the winter, as an adult, inside a woodpile or brush pile or behind a large flap of loose bark on a dead tree.

I wish I could explain the chemical change that occurs in this butterfly’s body fluid, preventing the water cells from freezing and bursting. Could this life-preserving chemical be something like the ethylene glycol which, when added to water in your car’s radiator, prevents it from freezing?

Quite a few other insects, including cluster flies and several other species of butterflies, can withstand below-freezing temperatures. In some years, the first adult butterfly I see, usually in March, at our home in the woods is the Milbert’s tortoiseshell, a small predominantly black, orange and white butterfly that has overwintered as an adult. Anglewings, such as the comma, are also spending the winter in diapause, their period of inactivity.

All butterflies of this temperate region spend the winter in diapause. Depending upon the species, this long cold period of inactivity may be in any one of the four life stages (egg, larva, pupa or adult).

The tiny hairstreak butterflies overwinter in the egg stage. Two of our favorites, the white admiral and the viceroy, spend the winter in the larva or caterpillar stage. Depending upon the latitude, a red admiral may overwinter in either the pupa or adult stage.

The only highly regular migratory butterfly from this part of the world is the monarch; it was the last generation of at least three during the summer of 2016 that had the instinct to migrate. Monarchs left northeastern Wisconsin, headed southward, in late September and ended up in the high, fir-clad mountainous region west of Mexico City.

Let’s say these migratory monarchs emerged from their chrysalises sometime in early September, migrated and, after wintering in a rather dormant condition at slightly above 50 degrees in Mexico, will head northward in early spring. These adults will mate and die around six to eight months after their lives as adults began last September.

The eggs laid by the female before dying will hatch and these offspring will find their way back to our state by late May or early June.

Several years ago, we had a phone call from a woman in Sister Bay excitedly telling of suddenly discovering a live mourning cloak butterfly flitting around in their living room – in the middle of winter! She asked, “How did it get here?” and “What should we do?”

I soon learned they heated their house with a woodstove, so I assumed the butterfly had been wintering in their outside woodpile and was scooped up within an armful of wood and brought into the warm house, where it soon revived and began to fly.

My suggestion on feeding was to put some sugar water in a spoon or jar cover, let the butterfly alight on a hand and ever so carefully uncoil its curled-up tongue to the sugar water. I had done this successfully several times in the past with monarch butterflies. We never did learn how the unusual winter visitor fared. I can’t visualize how that butterfly would have possibly survived had it been simply released outdoors into the below-freezing air.

We bask indoors in our warm home on this windy, frigid February day wondering where the November mourning cloak butterfly is at this moment. Hopefully on our walk out to the mailbox on a calm, sunny, warm March day this wonderful insect will nonchalantly sail above our heads, and we will be more awed and respectful than ever of this hardy but frail partner in nature.