Milkweed Musings

The Milkweed Sea

Mom was right about the butterflies. We drove out along the winding road towards the Cana Island Lighthouse, emerging from the darkness of the cedar grove into the bright sunlight of the beach ringing Moonlight Bay.  Hundreds of stalks of common milkweed in full bloom crowded the sand. We breezed right past our destination-the large rock enveloped almost entirely by milkweed-and realizing we had gone too far, slowed backed up to the small unmarked gravel parking lot. I emerged from the car into a wonderland of butterflies and bumblebees.

Dozens of them! I swear!

Dozens of them danced among the purple firework blossoms of milkweed. Like slips of bright confetti caught in a in an indecisive breeze, they’d alight, drift, settle again, while others rose lightly into the air. No delicate creatures, however, I heard the papery crash of wings as two collided and chased each other through the stalks. Mainly the vivid black-veined orange of monarchs, but also yellow striped swallowtails, blue and gold edged morningcloaks, the spangled orange, black, brown of fritillaries, creamy flashes of cabbage whites. All fluttered through the scene in constant motion. I stepped, entranced, into the sea of tall milkweed stalks as the butterflies briefly parted, then like water closing back in, dipped and soared around me again. Landing on one of the sturdy flowers drooping on its stalk, a monarch would clasp the edges with its black legs and unfurl a dark proboscis, or tongue, which it would gently prod the flower with until it found a well of nectar to drink deeply from. Across the road was the beach full of milkweed plants. And another flurry of black and orange butterflies. Photos come nowhere close to capturing the scene, but here are a few anyways:

Pearl crescent alighting on a plant

So.much.milkweed.

I am enthused

Tiger swallowtail and entomologist in paradise

The Deadly Table 

Snaking among the plants on the sand, I looked down and noticed the white, yellow and black caterpillar munching with singleminded gusto, with apparent joy in the fulfillment of its one job: to eat.

But eating milkweed is no simple task for a caterpillar. Through its veins, the plant pumps a sticky white ooze, full of toxic cardiac glycosides (so named - cardiac - for the organ impacted when too much is consumed). Not only toxic, the sticky latex can gum up the chewing mandibles of the careless caterpillar, glueing them shut so that the caterpillar can no longer eat. A critter less up for the task would be doomed. But this is the monarch caterpillar’s favorite food (favorite in the sense that it cannot eat anything else) so it has to use a couple of evolutionary tricks it has tucked up its…cuticle? Large caterpillars can bulldoze right through the plant’s defenses, and even use (sequester) those chemicals in its own body tissues to make it inedible to birds. This continues into the adult butterfly form, and the insect has that bright orange and black warning signs to inform them of this (young birds rarely make the same mistake twice).

But the caterpillar egg is the size a few grains of beach sand assembled together. And out of that egg comes an exceedingly tiny caterpillar. So how does this insect, smaller than a grain of rice, eat the leaves with veins like firehoses full of toxic glue? They eat themselves an island. The caterpillar, leaving itself a few supports, quickly snips the latex-filled veins in a circle around itself so that the goo it all rushes out and drains their little island of leaf so that it’s safe to eat! HOW DOES IT KNOW HOW TO DO THIS?! I admit, I don’t know, but its pretty damn cool!

This teeny monarch caterpillar on its island of safe  food

Looking up from the munching larvae, I notices the other insects swarming the flowers. Like steady ambling airships, the bumblebees also fed from the bounty of the milkweeds.
Buzzingly methodical, they floated their surprisingly airborne bodies between the flowers. Among their more charismatic six-legged counterparts, flies and beetles also abounded, drinking from the pulse of nectar. 

But why is this amazing plant, so stingy with its leaves, be so prodigal with its nectar?!

Well, my friends, this beneficent provider has a dark secret. 

I noticed, while I gazed into the plants, one small hoverfly somehow stuck to the flower, struggling to free its single leg that held it trapped on the plant. With some curiousity, I freed it, but could find no spider web or anything that held it in place. Here is where the milkweed plant continues to hold dangers for insect visitors. In each flower, there are small slits in which a waxy bundle of pollen, a pollinia, sits, waiting. While scrambling to get at the nectar treat, a leg or other part of the insect can slip into one of these slits which clamps it firmly, trapping the insect. A large insect like a bumblebee is strong enough to pull its leg from the tenacious grasp of the flower, bringing with it the pollonia. If the same hapless insect should stumble into the slit on its next flower, the pollen is transferred and the flower has accomplish its goal. If, however, like this poor fly, the insect is not large and strong enough, it remains stuck, like a coyote in a trap, and will either lose a leg escaping or remain chained to the milkweed flower! For a nice jargony more detailed description of this sneaky pollination strategy, see here. 

Insects beware

Beyond the Icon

Milkweed and milkweed conservation are grabbing the attention of the public, mainly because of the beloved monarch. I love monarchs, but there are so many insect species besides this icon of conservation that utlize this incredible plant. A majority of them are brightly colored to warn predators of the toxins they have so cleverly stored in their own bodies. This is call aposematic coloration and is very common throughout the animal kingdom. Nearly all of the insects you see feeding on milkweed (except for the ants tending their brightly colored aphid herds) are a vivid shade of orange or red.

Milkweed leaf beetles enjoying their afternoon

Red milkweed beetle (these guys squeak if you hold them!) : Photo credit, Liam McGranahan, loudonwildlife.org 

I hesitantly admit to photo credit for this blurry milkweed bug

The diversity of insect life supported by milkweed is amazing, yet I see websites shaming these endemic North American insects and asking how to destroy them because they threaten the food source of the monarch which COMPLETELY misses the point! Monarchs are the poster child, the charismatic minifauna that inspires people to conserve milkweed, but milkweed also needs to be conserved for the rest of these lovely creatures and their associates! The ecosystem is far wider and deeper than a single showy animal, lovable as it may be.

The true threat to these plants, food for so many, is habitat destruction and the wide-scale overuse of herbicides on crops that are genetically modified to withstand weedkillers (THERE is the main problem with GMOs in my opinion). Not only does the overspray and drift from these herbicides threaten milkweed populations, but also the trees and shrubs in our parks and landscapes. And...what does it do to us?  Planting this incredible plant is very important, but so is herbicide drift regulation and thinking hard about the way in which we practice agriculture. 

Speaking of activism...

I was so enraptured by the butterflies in this little patch of nature preserve, that I nearly forgot to visit the rock. The rock, so enveloped by the riot of milkweed it nearly disappears,  bears a plaque with the name of my mom's cousin, Jonathan Ela, inscribed upon it. For much of his life, Jonathan fought hard to protect amazing natural places like this one throughout Wisconsin and the world. He and his wife, Trish, worked to preserve areas like this in perpetuity, so milkweed can burst across the beach and butterflies can visit in riotous droves for summers into the future. The monarchs and all of the other butterflies and bees that visit that spot are grateful.