Narrowing Focus

The monarch butterfly (Danaus plexippus) population on the Mexican Monarch Reserve where they overwinter is the lowest since annual surveys began back in 1993. The oyamel fir forests provide a warm winter home for the monarchs, known for their great migration across North America. The population is down 59% from two years ago. In 1996, monarchs occupied 45 acres (18.2 ha) of forest. They now occupy 2.94 acres (1.2 ha).

Monarch butterfly wing Photo: Rare Giants

Monarch butterfly wing
Photo: Rare Giants

The entire migration process takes five butterfly generations to complete one full cycle, and over the past twenty years, fewer monarchs have been surviving the cycle to have their progeny return to the reserve.

The demise of the milkweed plant, mainly due to the use of glyphosate herbicides, means the butterflies are unable to find enough of their main food source. But extreme weather, deforestation and forest degradation, and regulatory rollbacks for protected areas also contribute to the dangers facing the species’ survival.

In Barbara Kingsolver’s novel Flight Behavoior, monarch butterflies disappear from Mexico almost entirely and find a new forest home in a completely unexpected location, alighting for a season before moving on. There’s always the hope that intensified efforts to replant milkweed and to strengthen protected migratory paths will help. And maybe, prior to the annual surveys, the monarch population experienced massive contractions that went unnoticed, only to recover again.

Mexican billionaire Carlos Slim has just announced a $100 million contribution to a variety of monarch programs. If there’s message here, it’s this: If you live in North America, go out and plant some milkweed. In your garden, on your balcony, on roadsides and byways. Sign a petition. Send a letter to your congressperson.

For now, the circle of monarchs retracts, a narrowing lens by which to observe these amazing creatures of long journeys on small wings.

Photo: Raul Gonzales

Close-up, monarch butterfly wing
Photo: Raul Gonzales

Pollinarium Paddles

Pollinarium on a copper pennyPhoto: ophis

Pollinarium twins on a copper penny
Photo: ophis

These images are of pollinaria, the strange and wonderful fertilization saddlebags of the milkweed, among other flowering plants.

A pollinating insect, a monarch butterfly for example, stands atop the milkweed flowerhead. Usually there would be a layer of pollen dust waiting to catch a ride, but in this case, a wee pollinarium detaches from the flower and hooks itself to the leg or mouth or antenna of the insect to be transported to another milkweed, where it then detaches itself.

Milkweed plants are the main food source for monarch butterflies. Once common, milkweed has been eradicated across large areas of its former native habitat, mostly due to farming and pesticides.



There’s a detailed description of how it all works here, but mainly, I like that the plant pollination structure looks like a paddle-legged insect itself.

Purple Milkweed (Asclepias purpurascens)

Purple Milkweed (Asclepias purpurascens)

Moment of Monarchs

Photo: Discovery Channel

Photo: Discovery Channel

When I was a child, we lived for a time in the U.S. Midwest. One autumn, I had the great good fortune of experiencing the migration of the monarch butterfly (Danaus plexippus). I didn’t even have to go on a field trip – the migrating flock flew right through our schoolyard in suburban Milwaukee, Wisconsin. The red brick school building, the featureless green lawns and black asphalt were, for a short time, obscured and transformed into a bright fluttering cloud of orange and black. We were led outside, class by class, to bathe in the butterflies. Of course, our science teacher couldn’t let a chance like that go unwasted, so we were also provided with capturing jars and small amounts of chloroform. Thus we became one more migratory hazard on the monarch’s annual 2000 mile (3200 km) trip from Canada to Mexico.

The monarch’s winter breeding ground in Mexico was discovered in 1976, allowing for better assessments of the overall population. Regular monitoring only began twenty years ago. And the overall trend for the past decade has been downwards.

According to this National Geographic article, the main causes are temperature extremes due to climate change, and the loss of the monarch’s main source of food as well as host plants for monarch eggs, the milkweed (Asclepias genus). The milkweed, a flowering plant with milky sap that is toxic to most animals, imbues the monarch with a natural defense – the butterflies themselves become toxic to predators. The once common milkweed has been eradicated over large stretches of the Midwest, partially due to herbicides and partially due to land conversion to farming. Monarchs are often seen around corn and soy fields where milkweed no longer exists.

What caught my eye was a comment on the National Geographic article: “Monarch butterflies and other pollinators (are) actually abundant and doing well in the herbicide tolerant GMO corn and soybean belt of the upper Midwest USA.” The commenter provides as proof a video he shot last year of hundreds of monarchs in a field. It’s hard to argue individual experience of abundance, even against evidence-based measurements taken over the course of years from various locations along the migratory route and the mothership grounds in Mexico.

When I was a kid and standing in that multitude of butterflies, it would have been virtually impossible to persuade me that the overall butterfly population might be in decline, or ever be in decline. Objectively, it felt like I lived in a bountiful universe of soft wings and color, but as it turned out, it was just a moment.

Annual migratory cycle over four generations Source: Journey North


National Geographic article – Monarch butterflies hit new low