Monarch Rescue

Nancy and I found the phone message light blinking in the kitchen after returning from a 30-mile bike ride. The message was from friend, Sarah. She was scrambling to solicit folks to collect monarch butterfly larvae (caterpillars) that were in danger of being harvested in a combine. She explained that a nursery owned by Minnesota Native Landscapes was going to combine a three-acre field of swamp milkweed pods within 24 hours and that the milkweeds in the field held many monarch larvae.

According to their website, Minnesota Native Landscapes is a “full service ecological restoration services company that designs and installs naturalized landscape features that are biologically diverse, ecologically and historically accurate and aesthetically pleasing for corporate, municipal and private landowners.”

Within two hours of Sarah’s recruiting call, we pulled into the nursery.  We were met by the affable nursery production manager, Keith Fredrick, who drove us to one of the back fields on the 80-acre nursery. As we drove he pointed out various plots of native plants being cultivated. Some of the plants are grown for direct transplanting and others, like the milkweeds, are grown for seed production.

The deep purple of a back corner field caught my eye. It was meadow blazing star (Liatris ligulistylis). Of the five species of blazing star in Minnesota, this one is the ultimate monarch butterfly magnet, a key nectar producer for adult butterflies.

Keith went on to explain that given all the recent publicity on monarchs and other pollinators, there has been a surge of interest in the public to procure milkweed seed. He added that next year this nursery will likely increase  production of various milkweed species to try and meet the demand.  He also remarked that the general public is not aware that there are several species of milkweed.

My favorite of the local milkweeds is the aptly named, butterfly weed in its flaming orange color. But on this day our focus would be on swamp milkweed.

Monarch butterflies can lay their eggs only on a milkweed plant. It doesn’t matter which species of milkweed, but it has to be a milkweed or nothing. The female is capable of laying about 300 eggs but she lays only one per plant to reduce feeding competition for the larvae.

I would argue that the monarch butterfly has snagged more media time this year than any other wild species in Minnesota, including the moose and walleye. Monarch populations have dropped 90% over the past 20 years.

In February of this year, the Center for Food Safety released an 80-page scientific report that made it clear that over the past two decades of increasing Roundup Ready crops, particularly corn and soybeans, in North America has nearly erased the sole source of food for the monarch butterfly. The dose of herbicides has made the genetically modified crops  “clean” of these supposed weed species. Sadly these chastised plants are the necessary nurseries for monarchs and other diverse insects.

Keith stopped the truck in front of the field. Very few of the broad rows of swamp milkweed were adorned with their characteristic pink flowers. Instead they bore the fruit, the slender pods, that would split and send their fluffy seeds to the winds if Keith waited too long to harvest them.

Soon Sarah and friend Vivian also showed up and we each slowly made our way, buckets in hand, down the rows looking for the monarch larvae. Within minutes our eyes were trained to pick  out the striped caterpillars in the foliage. We began to intersperse our conversation with exclamations of  “Got one here,” or “Here’s one!”

Delicately we removed the feeding larvae from the milkweed and set them in our buckets that were bedded with a thin layer of milkweed leaves.

For the first time in their short lives, many of the collected larvae were NOT eating but were climbing up the inside wall of our buckets. Normally these striped larvae don’t have to worry about escaping since they spend their two weeks as a caterpillar eating and only eating. The larvae go from being the size of a rice grain to nearly the size of a child’s little finger. During that span they will literally shed their skin five times to accommodate the rush of growth.

I recall reading about an entomologist who calculated that if an eight pound human baby had the same growth rate as a monarch larvae they would, after two weeks, be the size of a school bus!

Earlier in the summer, this field would have been producing monarch butterflies that could be the parents of the larvae we picked. The big difference between those June adult butterflies and these eventual butterflies, is that this late August-early September crop of monarchs will not be mating and producing eggs until next spring after a winter high in the mountains north of Mexico City.

In the earlier summer generations of monarchs, the reproductive organs  start to develop while they are larvae. The development is driven by the presence of a  juvenile hormone. But monarchs birthed in late summer have low levels of the juvenile hormone and they will remain low until the following spring. Only then does the overwintering monarch complete its sexual development. This delayed maturity is likely a strategy that conserves energy and makes it possible for them to direct their energies into migrating thousands of miles and then quietly overwintering.

By the time we finished our rescue efforts, the five of us had easily collected over 300 caterpillars.

Driving home, Nancy and I stopped on a back road near a healthy patch of the common showy milkweed and  relocated the larvae. We ambled down the shaggy ditch, setting one caterpillar at a time on its own milkweed plant.

It is humbling to believe that these pudgy little striped caterpillars contain the genetic material that will program  each monarch to lift off in less than a month and begin the long, dangerous flight to Mexico.

In comparison our 30-mile morning bike ride seems laughable.

Buena suerte amigos!! (Translation: Good luck friends!)

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