Backyard Naturalist: Milkweed, Monarchs & more

Published: 7/28/2020 1:32:16 PM

Wildlife conservation has long relied upon a concept known as “charismatic megafauna” – the idea that, by garnering support for a highly visible species with widespread appeal, you can also protect the ecosystem upon which it relies – and all the less charismatic species in that ecosystem, too. “Save the krill,” for instance, doesn’t lend itself well to bumper stickers, but humpback and blue whales feed almost exclusively on these tiny crustaceans. To save the whales, you also have to save the krill, and preserve the integrity of the oceans in which they both live.

Among the charismatic megafauna of the insect realm, monarch butterflies reign supreme. Their handsome coloration and complex, long-distance migration enchant even the most hardened entomophobes (bug haters), and for good reason: in all the world, no other butterfly migrates quite like the monarch.

The monarchs who float past the peak of Pack Monadnock each September – providing a welcome distraction for the hawk watchers on days when raptors aren’t riding thermals – are in the midst of a 3,000-mile journey to central Mexico, where they’ll wait out the winter. While our fields and forests are covered in snow, millions of monarchs cling to Oyamel fir trees on Mexican mountaintops, leaving only to drink water from nearby streams or, early in each new year, to mate. While we ski and skate and dream of summer, the entire population of North American monarchs is concentrated on about a dozen mountains in an area smaller than New York City, draped from their host trees like a living cloak.

In early spring, they venture north, but only so far as the southern United States. There, they deposit eggs on milkweed plants and, after seven or eight months of life on the wing, come to their end. In a remarkable evolutionary twist, their children, grandchildren, and great- grandchildren will only exist as butterflies for a mere two to five weeks. During that time, they’ll wing their way further north before laying their own eggs, a process that will repeat for up to five generations before the longer-lived monarchs of late summer make their way to Mexico once again.

In our neck of the woods, monarch butterflies – the great- or great-great-grandchildren of the overwintering Mexican mariposas – typically start to appear in mid-July, with monarch caterpillar abundance peaking in late July and August. In warm weather, monarchs grow from egg to butterfly in about a month, with five caterpillar stages (instars) and a period as a jade-green chrysalis (pupa) in between. Although monarch butterflies seek nectar from dozens of different wildflower species, monarch caterpillars are entirely dependent on milkweed.

In the last two decades, monarch populations have plummeted by more than 80%, largely due to habitat loss, climate change, and widespread pesticide use. Enter the monarch as charismatic megafauna, and a subsequent shift in perspective on milkweed. Once a much-maligned “weed,” milkweed is now being planted and protected in gardens, pastures, and conservation lands from Minnesota to Maine. Here in Peterborough, the Fremont Field conservation area and the open space adjacent to the community garden are both now managed with milkweed in mind. This summer, inspired by last year’s bumper monarch caterpillar crop, I planted native milkweed in my Harrisville yard for the first time. (If you’d like to do the same, check out the “Milkweed Market” at monarchwatch.org for ecoregion-specific plants that have not been treated with pesticides.)

In fact, milkweed has now become so prized as monarch fare that I’ve read several accounts of people removing other insects from milkweed plants in order to eliminate competition for monarch caterpillars. This, I think, is a good time to reflect on the value of biodiversity and on what biologist Anurag Agrawal calls “the milkweed village” in his book “Monarchs and Milkweed: A Migrating Butterfly, A Poisonous Plant, and Their Remarkable Story of Coevolution”.

Yes, we love monarchs and, yes, monarchs need milkweed – but, according to Agrawal, there are eleven other insect species who also specialize in milkweed, and scores more who feed on its nectar or hunt among its leaves. Examine a tender milkweed plant in early summer and you might find an ant tending aphids. Later in the season, you could discover the tufted bristles of a milkweed tussock moth caterpillar or spy a bumblebee or great spangled fritillary nestled among the blossoms. Humans, too, have found many uses for milkweed, including repurposing the fluff that carries milkweed seeds on the wind as pillow stuffing and fire starter.

Earlier this summer, Charley Eiseman – botanist, bug guy, and co-author of “Tracks & Sign of Insects and Other Invertebrates” – published this rather exasperated rant on his “Bug Tracks” blog after cutting a small amount of milkweed from his yard: “Don’t worry, there is plenty left for the monarchs, and the milkweed tussock moths, and the large and small milkweed bugs, and the milkweed long-horned beetles, and the milkweed weevils, and the milkweed leaf- mining flies – all of which are equally deserving of our affection and it drives me nuts when people want to kill or remove any non-monarch organism they find on their milkweed plants.”

Eiseman’s blog is dedicated to “bringing glory to Earth’s small and neglected creatures,” and I’d argue he’s done so quite eloquently.

Now is the perfect time of year to wander through your neighborhood milkweed patch, and to take a closer look at the exquisite globed flowers and latex-filled leaves. Marvel at the monarchs, but don’t ignore the beetles, weevils, leafhoppers, lacewings, dragonflies, ants, moths, bees, flies, aphids, or spiders. Diversity is beauty, and there’s no shortage of wonder to go around.

Brett Amy Thelen is Science Director at the Harris Center for Conservation Education.




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