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And onward they come in an endless string stretching hundreds of miles to the east, from Canada and the Eastern Upper Peninsula. Their line goes back countless millennia to a time when those who would change the environment lived in caves. How does this creature know to follow the beach as it begins its 2500 mile trip to the forests of north central Mexico?
Each year in August I go to the beach to witness their herky-jerky dance westward occasionally flirting with the water’s edge of a lake called Michigan. They flit and they flat past me as I stand motionless on the beach. If I’m still enough they may land on my head or my arm. The air to the east is filled with butterflies as far as can be discerned and every 15 seconds one passes by. In the Manistique area the best fly watching seems to be mid-August.
Most of the butterflies following the lakeshore west tend to pile up on the Stonington Peninsula where they rest before making the big water crossing, perhaps the most perilous part of their pilgrimage. They wait until a north or northeast wind aids them in their crossing. After hitting the Dorr Peninsula, in Wisconsin, the rest of their trip is over land all the way to Mexico. The only insect in the world that migrates like a bird will spend the winter in a grove of oyamel fir trees near El Rosario.
The monarch butterfly was first described by the early taxonomist Linnaeus in 1758. It is called a milkweed butterfly of the family Nymphalidae. Members of the family can be found on several continents. The monarch has the peculiar behavior of going south to overwinter. Most insects winter in place as adults or as eggs.
Since most insects live less than one year, how does the monarch return to its northern range to breed every year? Easy – the trip spans multiple generations, as many as four.
In late winter, a 7-month old butterfly in Mexico may breed and then begin the northward journey to Texas where she will lay her eggs on a milkweed plant. Two months later the new adults will wing farther north to find milkweeds for egg-laying. Monarchs that lay eggs in Michigan are the third or fourth generation of the year. It is thought that the offspring of these butterflies will return in four generations to breed in roughly the same location.
After the last generation of the year, born in Canada and the Northern United States, reach adulthood they face the arduous task of keeping their bloodline alive by going the distance, to Mexico, to winter. But how do they find this ancestral wintering ground, never having been there? DNA! No animal on earth better symbolizes the mystery of DNA messaging than the monarch butterfly.
Scientists have discovered the monarch possesses a time-compensated sun compass that depends on an internal clock based in their antennae. Recent research has also shown that monarch butterflies can use the earth’s magnetic field for orientation. But only DNA guidance can explain how 2 month old adults beginning a journey in Michigan will end up in the same exact trees their great, great grandparents used to overwinter a year earlier.
To win World War II, the allies had to break the Nazi communication codes. Because of our increasingly unpredictable climate, mankind will have to decipher the DNA code that governs monarch behavior, to get clues how to protect these beautiful and unique creatures.
Witness the Spectacular
The flutterby takes place in late summer and early fall on the north shore of Lake Michigan. Delta County’s Stonington Peninsula, and in particular, the cedar trees and lands surrounding the Peninsula Point Lighthouse Park at the end of the point becomes the resting place for thousands of monarchs waiting to cross Lake Michigan.
The Park is managed by the U.S. Forest Service’s Rapid River/Manistique Ranger District office in Rapid River. To get daily updates on the monarch migration on the Stonington Peninsula call (906) 474-6442, extension 110.
The life cycle of the miraculous monarch butterfly has four distinct stages:
- The eggs are laid on milkweed plants during spring and summer breeding months.
- The eggs hatch after 4 days revealing worm-like larvae, the caterpillars. The caterpillars consume their egg cases, then feed on milkweed and store a toxin called cardiac glycoside which is poisonous to birds and mammals. During the caterpillar stage, monarchs store energy to carry them through the non-feeding pupa stage. The caterpillar stage lasts around 2 weeks.
- In the pupa or chrysalis stage, the caterpillar spins a silk pad on a twig or leaf, and hangs from this pad by its last pair of prologs. It hangs upside down in the shape of a ‘J’, and then molts, leaving itself incased in an articulated green exoskeleton. At this point, hormonal changes occur, leading to the development of a butterfly (metamorphosis). The chrysalis darkens and the exoskeleton becomes transparent a day before it emerges, and its orange and black wings can be seen.
- The butterfly emerges after about two pupal weeks and hangs from the split chrysalis for several hours until its wings are dry. Meanwhile fluids are pumped into the crinkled wings until they become full and stiff. Finally the monarch spreads its wings, quivers them to make sure they are stiff, and then flies away, to feed on a variety of flowers, including milkweed flowers, red clover and goldenrod.