Monarchs and milkweeds

This pair are partners in nature’s tango.


Is there a butterfly more recognized and loved than the beautiful orange and black monarch? Most people are familiar with the basic monarch story: These beauties, like birds, are migrants who spend part of their lives in the North and part in the South — the Western population winters in Mexico, and the Eastern population primarily in Florida ( Unlike birds, which in their lifetimes make many migrations in both directions, individual monarchs only make the round-trip once. It is their children’s grandchildren that return South the following fall.

When you see a monarch fluttering about on the Vineyard in the summer, what is that butterfly’s story? According to the Vineyard’s premier pollinator advocate, Matt Pelikan, it depends on the month. In May, it may be a transient that was born somewhere South of here, and whose goal is farther North. In midsummer, it may be a first-, second-, or third-generation monarch born right here. In late summer, the butterfly you see may again be a transient from points North, or it may be Vineyard-born, headed for Florida, but in either case it will belong to the generation in which certain navigator and other genes have been expressed that will direct it not to hang around and breed, but to load up on nutrients and make the long migration.

Adapted as they are to this epic journey — longer than that of any other butterfly — and the production of multiple generations to complete a round-trip, if monarchs encounter disruptions to habitats and food sources anywhere along the way or in their breeding areas, not to mention actual poisons, their whole life cycle, and the species, is jeopardized. Typical potentially lethal disruptions are habitat loss from development, especially expanding agriculture that eliminates food sources, and increasing use of both pesticides and herbicides. Development in their breeding areas in the North also impacts food availability for both larvae and adults.

Milkweed plants are a nonnegotiable requirement for the North American migrating monarch, which is the subspecies Danaus plexipuss plexipuss. The evidence is that their larvae can eat the leaves of just three species of milkweed: Asclepias syriaca (common milkweed), A. tuberosa (butterfly weed), and A. incarnata (swamp milkweed). Female monarchs seek out these plants to lay their eggs. Most familiar to us here is common milkweed, with its bulky pods and seeds attached to silky gossamer “sails,” milky sap, and big, blousy, pinkish flowers. The monarch-milkweed marriage pact is sealed by milkweed’s toxicity to virtually every other organism other than about two other milkweed-specialist insects. All plant parts are loaded with lethal toxins, called cardenolides, that in turn make the monarch larvae and adults poisonous to potential predators. The brilliant wing pattern probably acts to signal, “Don’t even think about eating me!”

The Xerces Society for Invertebrate Conservation states that D. plexipuss plexipuss “is considered vulnerable to extinction, and the Eastern North American monarch population is considered critically imperiled.” Naturalists have reported startling declines in the number of monarchs overwintering in both Mexico and Florida. According to the Xerces Society, “Milkweed loss across much of North America is believed to be a major factor contributing to monarch population declines” ( We have all noticed this steep decline.

In a quiet Vineyard Haven neighborhood, Robyn Lopes-Beaulieu is giving monarchs a helping hand. She has created in her lawn a series of beds planted with butterfly weed, one of the milkweed species that monarch larvae eat, and other wildflowers as nectar sources for the adults. Her aims are to protect the eggs from predators such as birds; provide the food and shelter they need to hatch and grow from tiny larvae to fat, 2-inch-long caterpillars; enjoy the spectacle as each butterfly finally emerges from its chrysalis; then release them. “This year I released a total of 41 monarchs,” she says.

In the Lopes-Beaulieu household, love of science and nature is a family affair. “I was inspired to start raising monarchs by my mother, Barbara Lopes, a longtime teacher in the Tisbury School, who raised and released butterflies with her first-graders,” she says, “and my daughters love science.” They have become as enthralled as their mother and grandmother with the slowly unfolding monarch drama. Raising monarchs has increased Lopes-Beaulieu’s awareness of other denizens of her butterfly havens. Spotting a small brown butterfly on a blade of grass, she snaps a photo with her phone and goes right to the Seek app (similar to iNaturalist). “It’s a small copper,” she tells me.

Lopes-Beaulieu has worked out a reliable system for successfully raising monarchs: “My main tools, apart from the plants I grow, are a Restcloud Insect and Butterfly Habitat Cage Terrarium Pop-Up and a few red plastic Rescue! Fruit Fly Traps. You can get them from Amazon.”

In early summer, she starts examining her milkweed leaves for eggs, and when she finds one, she carefully cuts the stem and sticks it in one of the holes of the fruit fly trap, with water in the bottom. Eventually the egg hatches, and a tiny larva emerges, eats the egg case, devours a u-shaped hole in the leaf, and keeps going until it has munched away all the leaves. Lopes-Beaulieu brings new milkweed stalks for her caterpillars as needed. Each caterpillar sheds its exoskeleton five times to continue growing bigger: five instars, as they are called. Instar No. 5 is the stage that will form a chrysalis.

She installs a twig in her terrarium as a ladder for the caterpillar to crawl up to the top, where it firmly attaches itself, partly via a fine webbing it spins. When it sheds its final exoskeleton, underneath is a hard, green shell — the chrysalis, or pupa. The chrysalises hang, eerily and expectantly, for 10 to 14 days, undergoing mysterious processes. The next time we see movement is when a chrysalis cracks, and a butterfly slowly struggles out, uncurls its proboscis, and unfurls its new wings — still undersize until, flexing them, it pumps fluid from its abdomen into them. This can take up to 15 minutes. See this miracle unfold in these videos:




When their wings are dry, the butterflies fly off in search of sustenance. Lopes-Beaulieu is planting more native nectar plants, especially common milkweed. (See “Monarch Nectar Plants Northeast,” the Xerces Society’s useful, printable chart, with keyed color photos.) A very surprising fact is that although milkweed plant parts are toxic, their flowers’ nectar is some of the most nutritious insect food out there, and is used by many pollinators. It takes two or three years to establish a planting of common milkweed, but once established, they are extremely robust: Their taproots can be 6 feet deep, and they also have extensive systems of lateral rhizome roots, which can send up new shoots.

“I am really frustrated,” Lopes-Beaulieu says, “when I see landscapers and caretakers mowing down stands of milkweed that my monarchs — and other pollinators — need.”

Landscaper, spare those milkweeds — in fact, please plant more! Milkweed seeds are maturing now, in the latter half of October, and sailing off on the breeze. Human intervention can increase the germination rate. Wild Side columnist and naturalist Matt Pelikan suggests, “Collect mature seeds and distribute them where you want your milkweed bed, with a light covering to keep them in place. They mustn’t be too insulated, because they need cold — called stratification — and adequate light to germinate in the spring.”

The monarch and the milkweed are avatars of the extraordinarily complex chemical relationships between pollinators and their plant partners. Have you heard of the butterfly effect? “The flapping of the wings of a butterfly can be felt on the other side of the world.”

In the case of the monarch, what happens on Martha’s Vineyard definitely affects events from Mexico to the Maritimes, and myriad points in between (see