As a child growing up in Minnesota, I learned about the amazing migrating Monarch butterfly. Of course, I also learned about their endangered status and how important it was (and still is) to protect their habitat. I remember a stand of milkweed plants at the edge of a neighborhood park where my siblings and I would collect the dried seed pods with their silky-soft down attached to each flat brown seed. We would pull the fluff out by the handful and scatter them in the wind, laughing as they swirled around us… until the wind shifted and we got on a faceful of the fluff. Strangely, I don’t recall ever seeing an actual Monarch butterfly.
When I moved to the Pacific Northwest, I never had a place that was sunny enough to grow milkweed. But now that I live in Florida, I have a yard, I have sun, and I can plant my butterfly garden! I researched what nectar plants were good for bees and butterflies and planted Mexican Torch flowers, Blanket Flowers, Black Eyed Susans, Beach Sun Flowers, and of course, Milkweed!
For most of the summer, I only saw Gulf Fritillary butterflies flitting over my two passion flower vines and occasionally sipping nectar from the flowers I had planted. Then sometime in late September, I saw my first Monarch! It was utterly thrilling to see as many as three or four at a time nectaring on the Torch flowers and laying eggs all over the milkweed plants!
In just a few days, the eggs had hatched and gorgeous striped monarch caterpillars were munching away on leaves.
According to this helpful infographic by Journey North about the Monarch butterfly life cycle, I should see some chrysalises in the next week or so.
Recently, I noticed that I hadn’t seen any adult Monarch butterflies in a while – I’m estimating that it’s been about 1-2 weeks since I’ve seen them.
This got me thinking, and I realized that everything I know about Monarch butterflies is based on the northernmost portion of the Monarch Butterfly migration path.
Clearly, I needed to do some research on the life cycle and habitat needs of Butterflies in Florida.
This map by the Xerces Society shows the migration paths and habitat regions of the monarch butterfly. Although Florida does have a non-migratory population of Monarchs and some migrating monarchs overwinter in southern Florida, most Monarchs should be passing through Florida on their way south in fall.
Along the way, migrating Monarchs stop for sustenance from the nectar of certain native flowers and then move along towards their annual overwintering sanctuaries in central Mexico. In spring, some parts of Florida may see the Monarchs passing through on their way to spring breeding grounds.
Of course, it’s more complicated than a simple migration south in fall and then back north again in spring. Monarch butterflies are long-lived butterflies so a single adult butterfly can lay multiple generations of eggs. Some generations will live, mate and die in one of their breeding grounds.
It may be third or even fourth generation butterflies that actually migrate south again when summer ends. The important thing here, is that when summer ends, the Monarch butterflies migrate south to their sanctuaries.
Of course, if you’re reading this you probably already know what I only just learned over the past few days. Monarch butterflies are facing a serious problem with a protozoan parasite, Ophryocystis elektroscirrha, or OE for short. OE requires a host body to reproduce but once it does, it produces spores that can live outside the host body. These spores can then be spread from the adult butterfly to the milkweed plants that get eaten by caterpillars. Once inside the body of the caterpillar, the parasite’s life cycle begins again.
The majority of the actual damage done by this parasite occurs during the chrysalis stage. When the adult butterfly emerges, it may have a number of problems including deformed or crumpled wings, smaller size, weakened cuticle on the abdomen resulting in dehydration, decreased flight endurance, and impaired mating abilities for males. (Project Monarch Health).
The decreased flight endurance is a key part of the problem. Migration acts as a filtering mechanism – only the strongest and healthiest butterflies make it to the overwintering sanctuaries. Without migration, the infected butterflies are able to mate and continue spreading the parasite.
Monarch butterflies rely on several seasonal cues to begin migrating, one such critical cue is the dieback of their host plant in fall. The native species of milkweed all do this, however, there is a non-native specie of milkweed commonly called “tropical milkweed” that has beautiful, showy blooms year round.
When Monarchs come across this big, beautiful showy milkweed plant, they tend to settle in for the winter rather than continuing their migration. This pattern (or anti-pattern) has resulted in catastrophically high infection rates among Monarch butterflies in Florida.
There are three major monarch populations in North America:
Source: Project Monarch Health
- The eastern migratory population (yellow).
- The most studied population
- Migrates in fall to Mexico and returns north in the spring
- Lowest level of infection; less than 8% are heavily infected with OE
- The western migratory population (orange).
- Lives west of the Rocky Mountains
- Migrates in fall to the coast of California.
- Moderate level of infection; 30% of these monarchs are heavily infected with OE.
- The non-migratory population in South Florida (green).
- This population breeds year-round and does not migrate.
- This “resident” population has the highest level of infection; over 70% of the population heavily infected with OE.
Guess what kind of milkweed I planted? Yup. Tropical milkweed. After I recovered from my initial horror and dismay, I came up with a plan.
Step number 1; remove any and all seedpods from the tropical milkweed plants and dispose of them so the seeds cannot grow.
Step number 2: monitor the caterpillars already on the current milkweed plants and collect any chrysalises I find. I’ll bring these inside and monitor them for signs of OE. The Monarch Health Project has instructions for testing butterflies for OE here.
Step number 3: Remove all the tropical milkweed and replace it with native milkweed species.
Hopefully this will work! I’ll post updates as my plan progresses.
References:
Jepsen S., Schweitzer D.F., Young B., Sears N., Ormes M., Hoffman Black S.. March 2005. Conservation Status and Ecology of the Monarch Butterfly in the United States. Prepared for the U.S. Forest Service by: NatureServe Arlington, Virginia and The Xerces Society for Invertebrate Conservation Portland, Oregon. https://www.xerces.org/publications/scientific-reports/conservation-status-and-ecology-of-monarch-butterfly-in-us.
Journey North. https://journeynorth.org/monarchs/resources; Date accessed 10/20/21.
Nestle, R.; Daniels, J.C.; Dale, A.G. Mixed-Species Gardens Increase Monarch Oviposition without Increasing Top-Down Predation. Insects 2020, 11, 648. https://doi.org/10.3390/insects11090648
Project Monarch Health. https://www.monarchparasites.org/oe; Date accessed 10/20/21.
Wade L. January 13, 2015. Plan to save monarch butterflies backfires; The wrong kind of milkweed is stoking parasite infections. Science.org. doi: 10.1126/science.aaa6337
Williams, M.J. 2015. Monarchs Make Florida Home. Natural Resource Conservation Service of Florida, https://www.nrcs.usda.gov/wps/portal/nrcs/detail/fl/newsroom/releases/?cid=NRCSEPRD363613. Date accessed 10/20/21.
Xerces Society for Invertibrate Conservation. Monarch Butterfly Conservation. https://xerces.org/monarchs. Date accessed 10/20/21.
Erica Lauer Vose 
