- Barbara Murphy
The Festival and the Monarch
Engagement with the natural world—this is the ethos of MLT's Habitat For All (HFA) program. We believe that engagement is the first step in reigniting a personal commitment to the care of the environment.
The annual Monarch Festival is a full day of engagement. It is a day to touch, smell, discover, learn, and interact with nature. Monarch butterflies are perfect ambassadors by providing engagement at so many levels — caterpillars, chrysalids, nectar plants, milkweeds, plus their incredible migration.
Let's begin this cyclic event in Mexico where the Eastern Monarch overwinters. Monarchs that live east of the Rocky Mountains overwinter in rare oyamel forest ecosystems located on one of 12 mountain sanctuaries in Mexico. Monarch butterflies appear to be adapted to the same ecological conditions as the trees - it is cool and relatively moist at high elevations when this region of Mexico is parched during the dry season. The cool temperatures slow butterfly metabolism allowing them to conserve their fat reserves. And the condensed morning fog provides needed moisture. The butterflies remain in the forest for 4-5 months. Interestingly, annual monarch populations are based on the total forest area used by monarchs each winter. It certainly beats counting them! In 2020, one of the monarchs tagged at Valentine Farm was recovered in Mexico!
The migration north
Around the time of the spring equinox, the cues to begin migrating occur. Northern migration is a delicate dance - waiting long enough to ensure adequate habitat north, but not too long and risk using up fat reserves or being caught in Mexico's rainy season.
Mating begins as temperatures rise. Unlike many insects, monarch adults live for 2-6 weeks after mating. Once mated, butterflies move north feeding on nectar plants and searching for milkweed to lay eggs on. Milkweeds are identified through sensors in their feet. Cold weather, tropical storms, high winds, and frosts can delay migration and reduce the potential size of the first generation. Typically it is the third generation of monarchs that we see in western Maine. The first generation is born in Texas. This generation mates and flies through a wide swath of the midwest to lay its eggs creating the next generation. This second generation arrives in New England in late July, mates and their offspring, the third generation, (sometimes it is the 4th generation) are the super generation of butterflies which travel all the way to Mexico. These are the butterflies that we catch and tag with small stickers as part of Monarch Watch.
If successful in finding adequate nectar sources and milkweed to lay eggs on, females lay one egg at a time, many per day. The eggs are the size of a pinhead, conical with ridges. The egg hatches in approximately 4 days.
Caterpillar growth is measured in instars. Each caterpillar goes through 5 instars from egg to the final caterpillar before a chrysalis is formed.
1st instar - 2-6 mm
2nd instar - 6-9 mm
3rd instar - 10-14 mm Each instar lasts between 3-5 days
4th instar - 13-25 mm
5th instar - 25-45 mm
The 5th instar is the final caterpillar stage before forming a chrysalis. In addition to its large size, 5th instars chew a shallow
notch on the milkweed leaf they are eating, resulting in the leaf falling in a vertical direction. The caterpillar now leaves the milkweed to find a sheltered place to hang in the shape of the letter J for 6 hours to form its chrysalis, the jade green "suitcase" with the gold thread on top. After 8-14 days, an adult monarch butterfly appears, pumps its wings and looks for nectar to feed on.
The migration south
The monarchs that arrive in Maine in late summer are part of the super generation, the group of monarchs that fly over 3,000 miles to Mexico. Unlike the summer generations which live for 4-6 weeks, this final generation lives for 8-9 months, does not mate until next year, and endures many perils during its lifetime.
The success of the southern migration begins with the size of the caterpillar that forms the super generation adult butterfly. Large caterpillars result in big, healthy butterflies with fat reserves and fat reserves play a critical role in monarch winter survival.
When the temperature begins to fall and day-length shortens, the flight to Mexico begins.
Monarchs travel only during the day. They congregate in tree roosts each night.
The adult butterflies feed only on nectar for the entire journey completely dependent on a trail of flowers to keep them well nourished.
It is thought they navigate through sensors in their antennae, and by the angle of the sun. (Remember, this generation has never been to the overwintering site in Mexico). Can you imagine navigating south using the New Jersey turnpike as a guide?
Tagging has shown they stop frequently to rest and feed and may wait for good weather conditions
Glider pilots have reported monarchs as high up as 11,000 feet, fishing boats on the Gulf of Mexico have reported sightings as well.
Most monarchs arrive in Mexico during November-December, typically 3-4 months after the start of their journey.
Then the cycle begins again
If you want to learn more about monarch migration, visit https://journeynorth.org/monarchs