Every summer we see monarch butterflies flutter delicately from plant to plant. With their distinctive bright orange wings, and black and white markings, it’s difficult to miss them. But as the cold weather approaches, and the leaves begin to change colour, monarchs make their way to warmer weather.
Though monarch butterflies can be found in South America, the Caribbean, Hawaii, and Australia, it’s only the North American monarchs who migrate once the summer season starts to fade away. As they make their way to vacation destinations like Mexico and California, these butterflies fly at speeds ranging between 19 and 40 kilometers an hour, flapping their wings — slower than most butterflies.
And like most humans, these butterflies don’t like travelling in the cold. In order for them to be able to begin their journey, the weather needs to be around 15 degrees celsius so that their flight muscles are warm enough to fly.
One of the most fascinating aspects about these eccentric butterflies is that they have the longest migration of any other insect, and their migration process lasts over several generations.
“The monarchs that migrate south are not the same monarchs that migrate back north,” says Diane Debinski, a professor and head of the department of ecology at Montana State University. She mentions how these butterflies manage to transfer their migratory routes from generation to generation. The memories then, are not stored in an individual butterfly, instead, they are transferred between generations.
To put it in perspective, Jennifer Tremeer, an instructor for the Monarch Teachers Network, explains how the first monarchs of the summer are the great grandchildren and sometimes even the great great grandchildren of the monarchs that left our backyards and parks the previous fall. She describes how one monarch could make a trip to Mexico, but it takes several generations of monarchs to return to Canada the following summer.
But how do monarchs decide whether they want their next winter getaway to be in Mexico or California? According to Tremeer, North America has two distinct populations of monarchs. While 95 per cent live on the east side of the Rockies, 5 per cent live on the west. Those who live on the east migrate to Mexico in search of a specific micro-habitat on oyamel fir trees that are located 10,000 feet above sea level in the Sierra Madre mountain range. The other 5 per cent travel to the Pacific Grove area of California in search of eucalyptus trees.
Apart from their phenomenal migration, these butterflies use their eyes to locate flowers, their antennae to smell the nectar, and small receptors that are lodged into their feet to taste the sweetness of the nectar. These receptors are called “tarsi.”
Monarchs and Milkweed
Tremeer, who also works at the Cambridge Conservatory, has been raising monarch butterflies for nearly 20 years and just last weekend, the Conservatory released over 120 monarch butterflies that she raised from eggs and caterpillars she had found on her property.
Monarch butterflies can lay around a maximum of 300 eggs over their entire lifespan, which in the summer generation, ranges from 2 – 5 weeks at the rate of one egg at a time — that’s a lot of baby butterflies! But unlike other butterflies who lay eggs in groups or clusters, like the mourning cloak, monarchs tend to prefer laying one egg per milkweed plant. This means that each monarch caterpillar usually doesn’t have to share its food with his siblings – but it does mean more work for mamma. She must now fly around searching for 300 unoccupied milkweed plants to lay her eggs.
Because milkweed plants are essential for most monarchs, it is crucial to be aware of how humans can help.
Over the years, the number of monarch butterflies have been declining and one theory as to why is because there has been an increase in herbicide-based agriculture, which has been destroying monarchs’ prime source of nectar: milkweed.
Their decreasing numbers have inspired habitat conservation for pollinators in the form of ‘Monarch Waystations,’ says Debinski. These ‘Waystations’ are usually smaller garden plots, but other restoration efforts for monarchs can be up to hundreds of acres. “We need more people who are interested in conserving rare insects, as they are in conserving pikas and polar bears,” says Debinski.
Conserving these butterflies can be as simple as planting milkweed and nectar plants.
Tremeer strongly believes: “If you plant it, they will come.”