“The caterpillar does all the work, but the butterfly gets all the publicity.”
— George Carlin
Monarch butterflies undergo a complete metamorphosis, or a four-part life cycle. Life begins as a tiny egg, which soon hatches an elfin larva, or caterpillar. The caterpillar does much of the heavy lifting on the road to butterflydom. It is an eating machine, increasing its body mass scores of times as it grows through, in the case of the monarch, five molts.
Life is fraught with peril as a caterpillar, and many are eaten by predatory insects, birds and even some amphibians and reptiles. Less than 10% of caterpillars survive to enter phase three, the chrysalis. This seemingly low survival rate is better than most species of butterflies and moths. Monarchs’ host plants are milkweeds, which are infused with toxic cardiac glycosides. The caterpillar, and the butterfly to come, sequester these poisons, which render them distasteful if not unpalatable to many would-be predators.
Dozens of monarchs in a silver maple.
Butterfly chrysalises are magical chambers of transformation in which the tubular caterpillar morphs into an entirely different body form. The monarch takes chrysalis creation to a high art form. The two-inch-long shiny case is a beautiful emerald green, adorned with a showy black and gold band. As the chrysalis ages, it becomes opaquer and toward the end, the black and gold butterfly can be seen within.
After about two weeks, the butterfly emerges. From egg to butterfly takes about a month.
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America’s best-known butterfly is a source of endless fascination. Perhaps the most incredible aspect of the monarch is its incredible migration. Virtually all monarchs breed in North America north of Mexico, some as far north as southern Canada. Excepting a small resident population in southern Florida, the butterflies stage a mass migration to oyamel fir forests in the mountains of central Mexico. Some butterflies travel over 3,000 miles from their site of origin.
Once ensconced in the Mexican fir forests, the gregarious monarchs blanket the trees. Accurate estimates of individual numbers are nearly impossible, so researchers measure the acres covered by the butterflies. Assessments of the wintering population began in 1993, and the highest number of butterflies was in winter 1996-97, when a whopping 45 acres of forest was cloaked in butterflies.
As time has elapsed, it’s clear that monarchs are on a downward spiral. The lowest winter count was in 2013-14, when only little more than an acre and a half of forest harbored butterflies. Winter 2023-24 found butterflies in only 2.2 acres of oyamel forest. For the first decade of wintering ground surveys, monarchs covered an average of 21 forest acres. For the last decade, that’s plummeted to 11 acres. An estimated 80% of the migratory eastern population of monarchs has vanished since surveys began.
Ever-increasing use of herbicides and insecticides, habitat loss due to various development, disease and degradation of wintering habitat are all key contributors to monarch reductions.
Jim McCormac is a natural historian and columnist.
But there is much that people can do to help. And some people are helping on a grand scale.
Lorene and Robert Miller of Plain City, in Madison County, farm 120 acres. Their farming practices are organic: no fertilizers or pesticides, use of cover crops, composting to increase soil health and crop rotation. Every three years, the Millers plant large swaths of their land in red clover, which enriches nitrogen in the soil. After the growing season, the clover is tilled into the soil, further enriching it.
A fabulous benefit of the clover crops is the formation of enormous migratory congregations of monarchs. The butterflies are drawn to the clover flowers, and gather there en masse, and form impressive nighttime roosts in an adjacent windbreak of Norway spruce and silver maple.
The Millers first documented the monarch swarms six years ago, then again three years ago, and in keeping in sync with the clover crop cycle, they are back again this fall.
I visited the Miller farm on Sept. 10 and was stunned by the spectacle of 1,000 or more monarchs swarming the trees as they came in from the fields near dusk. Dozens of fellow butterfly enthusiasts were there as well.
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One visit was not enough, and I returned with Shauna on Sept. 14. That’s when I made the accompanying photo. The butterflies in my shot are just the tip of the lepidopteran iceberg. Almost as cool as seeing the butterflies was observing the reactions of the onlookers. Hundreds of people from as far as Kentucky and Michigan have visited. Admirers formed a ring around a favored silver maple roosting tree, staring in slack-jawed reverence at the scores of beautiful butterflies.
The migratory swarm will soon disperse, probably by the time that you read this, and the butterflies will continue to work their way south to the Mexican fir forests. They’ve still got about 1,700 miles to go to get there.
Major thanks to the Miller family for allowing so many visitors to come revel over the monarchs. And even more thanks for their excellent environmental stewardship and strong land ethic.
Naturalist Jim McCormac writes a column for The Dispatch on the first and third Sundays of the month. He also writes about nature at jimmccormac.blogspot.com.
This article originally appeared on The Columbus Dispatch: Nature: Monarch butterflies flock to one central Ohio farm
