Today I saw the first Mourningcloak butterfly of spring! I was so excited, because I just learned about the habits of this amazing insect last summer. The following is an article I wrote last year about the overwintering habits of several species of lepidopterans in my home state of Illinois, but I believe all these butterflies and moths are also found in Georgia, where I am currently residing. (Photo courtesy of Wikipedia Commons)
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"As autumn establishes herself here in northern Illinois, and the trees show off one last burst of color before fading into their winter slumber, we say goodbye to many other brightly-hued summer residents: the butterflies and moths. But are they really just summer residents?
In fact, many of our lepidopteron friends are closer to us than we realize as we sled down hills and toast the New Year. The Mourningcloak butterfly (Nymphalis antiopa), with its dark brown to maroon colored wings resembling funeral attire, outlives Old Man Winter himself by hibernating in the nooks and crannies of trees and leaves on the forest floor. This butterfly spends 10-11 months of its life as an adult after leaving its chrysalis in June or July, and when it emerges from hibernation in March, it mates and lays eggs to produce the next generation. Contrary to its name, this butterfly is not an indicator of death, but of the living spring creeping upon the land!
The Mourningcloak accomplishes this feat using what the online Magazine Nature North calls a built-in 'anti-freeze system.' Among other tactics, the insects maintain high levels of sugars to lower the freezing temperature of the water in their systems (the sugars bind to the water, preventing it from forming ice crystal structures). They also try to stay in dry places to avoid contact with the ice in the environment around them. These methods protect the insect’s most delicate organs, while other less critical parts may freeze and then thaw again in the spring with no overall harmful effect.
Like the Mourningcloak, the well-known and well-loved Monarch butterfly (Danaus plexippus) can also live a long adult life. While most members of this species only fly an average of 4-5 weeks, producing several generations during the summer months, the final group of adults delays reproduction and migrates in September and October to a single preserve in mountainous central Mexico. After a journey of 1-3,000 miles the insects hibernate in the oyamel fir trees in the Lomas de Aparicio, awakening in February to breed and begin the return migration north. They won’t make it all the way, however. They lay their eggs soon after leaving, then die after having lived 7-8 months in the adult form. The new generation will continue the migration for a few weeks, mating and laying eggs to produce more butterflies that will travel even further north. Eventually, the monarchs reach Illinois in April.
The big question is: how do migrating monarchs know where to go when they have never been to Mexico before, and their parents and grandparents never even dreamed of its existence? The answer is still a mystery, but research is revealing more about the methods used for the sojourn itself. In experiments begun by researcher Sandra Perez, the monarchs were shown to be sensitive to both the earth’s magnetic field and the time of day as indicated by the sun’s daily course. Monarchs that were put through a cycle of light and dark different from the outside environment became disoriented when released outside, because they were no longer on the sun’s time schedule. Likewise, monarchs exposed to a reversed magnetic field also flew in the wrong direction, heading northeast instead of southwest.
Having considered two of Illinois' more familiar butterflies, it would hardly be appropriate to neglect the moths. For many people, one of autumn’s little joys is the sight of the black and russet banded caterpillars known as 'Woolly Bears' (Isia Isabella). These insects overwinter in the caterpillar stage, entering their cocoons in the spring and flying as adults only in the summer months. The less common but also admired Luna moth (Actias luna) spends the cold season as a pupa enveloped in a cocoon, having entered a state known as diapause, where the insect’s development 'pauses' until environmental conditions are more favorable. The shortened days and cooler temperatures of fall are two of the predominant signals that precede this period of dormancy.
So why do butterflies and moths have such unique and varied ways of coping with winter? Why don’t they all just do the same thing? In ecological terms, it is because each species has its own methods of surviving that allow it to compete for the resources it needs, including food and territory. The Mourningcloak, for example, has a head start on all other Illinois butterflies by being the first to become active. And for our own part, as Sharman Russell says in her book, An Obsession with Butterflies: '[W]e, who live by myth, who live in fear of change and in fear of death, are privileged to see this metamorphosis over and over, a common thing…'
So as cold weather approaches and you snuggle under blankets to dream of warm sunny days full of flowers, remember that a butterfly could be doing the very same thing right outside your door, waiting patiently for the spring that always returns again."
The Mourningcloak accomplishes this feat using what the online Magazine Nature North calls a built-in 'anti-freeze system.' Among other tactics, the insects maintain high levels of sugars to lower the freezing temperature of the water in their systems (the sugars bind to the water, preventing it from forming ice crystal structures). They also try to stay in dry places to avoid contact with the ice in the environment around them. These methods protect the insect’s most delicate organs, while other less critical parts may freeze and then thaw again in the spring with no overall harmful effect.
Like the Mourningcloak, the well-known and well-loved Monarch butterfly (Danaus plexippus) can also live a long adult life. While most members of this species only fly an average of 4-5 weeks, producing several generations during the summer months, the final group of adults delays reproduction and migrates in September and October to a single preserve in mountainous central Mexico. After a journey of 1-3,000 miles the insects hibernate in the oyamel fir trees in the Lomas de Aparicio, awakening in February to breed and begin the return migration north. They won’t make it all the way, however. They lay their eggs soon after leaving, then die after having lived 7-8 months in the adult form. The new generation will continue the migration for a few weeks, mating and laying eggs to produce more butterflies that will travel even further north. Eventually, the monarchs reach Illinois in April.
The big question is: how do migrating monarchs know where to go when they have never been to Mexico before, and their parents and grandparents never even dreamed of its existence? The answer is still a mystery, but research is revealing more about the methods used for the sojourn itself. In experiments begun by researcher Sandra Perez, the monarchs were shown to be sensitive to both the earth’s magnetic field and the time of day as indicated by the sun’s daily course. Monarchs that were put through a cycle of light and dark different from the outside environment became disoriented when released outside, because they were no longer on the sun’s time schedule. Likewise, monarchs exposed to a reversed magnetic field also flew in the wrong direction, heading northeast instead of southwest.
Having considered two of Illinois' more familiar butterflies, it would hardly be appropriate to neglect the moths. For many people, one of autumn’s little joys is the sight of the black and russet banded caterpillars known as 'Woolly Bears' (Isia Isabella). These insects overwinter in the caterpillar stage, entering their cocoons in the spring and flying as adults only in the summer months. The less common but also admired Luna moth (Actias luna) spends the cold season as a pupa enveloped in a cocoon, having entered a state known as diapause, where the insect’s development 'pauses' until environmental conditions are more favorable. The shortened days and cooler temperatures of fall are two of the predominant signals that precede this period of dormancy.
So why do butterflies and moths have such unique and varied ways of coping with winter? Why don’t they all just do the same thing? In ecological terms, it is because each species has its own methods of surviving that allow it to compete for the resources it needs, including food and territory. The Mourningcloak, for example, has a head start on all other Illinois butterflies by being the first to become active. And for our own part, as Sharman Russell says in her book, An Obsession with Butterflies: '[W]e, who live by myth, who live in fear of change and in fear of death, are privileged to see this metamorphosis over and over, a common thing…'
So as cold weather approaches and you snuggle under blankets to dream of warm sunny days full of flowers, remember that a butterfly could be doing the very same thing right outside your door, waiting patiently for the spring that always returns again."
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