The monarch butterfly lifecycle is one of the more remarkable things I have witnessed from this piece of land, and I have been watching it play out every fall for years. That bold orange and black with white spots along the head and wing margins is unmistakable, even at a distance, even when one is drifting over the meadow on its way somewhere else entirely.
I have been seeing a few lately, pausing for nectar at Becky’s flowers or moving south across the open fields. But their numbers are way down from what they used to be. I remember when the trees at the pond would be covered with hundreds of them resting together in the afternoon light. I wish I had taken a picture.
Key Takeaways
It Starts with an Egg on a Milkweed Leaf
The full monarch butterfly lifecycle begins small enough to miss entirely. The egg is pale and ridged, about the size of a pinhead, laid singly on the underside of a milkweed leaf. A female will lay hundreds of them across many plants, never clustering them in one place.
Within a few days the egg hatches into a tiny caterpillar that immediately begins feeding on the milkweed leaf it was born on. Everything that comes next depends on that plant being there.
The Monarch Butterfly Caterpillar and What It Eats
The monarch butterfly caterpillar is easy to identify once you know what you are looking for. Yellow, white, and black bands run the length of the body, with paired black filaments at the head and tail that give it an almost theatrical appearance. If you have milkweed growing anywhere on your property, it is worth checking the undersides of the leaves.
The caterpillar feeds exclusively on milkweed, and that diet is doing more than just fueling its growth. Milkweed contains cardiac glycosides, toxins that the caterpillar ingests and stores in its body rather than breaking down. Monarchs have evolved a way to neutralize compounds that would kill other insects outright. The result is that both the caterpillar and the adult butterfly are distasteful to most predators. The bright colors are a warning, and most birds learn it quickly.
From Chrysalis to Butterfly
When the caterpillar is ready to transform, it forms a chrysalis. The casing is a soft jade green with a delicate ring of gold dots near the top, one of the more beautiful things you will find hanging from a stem or a fence post if you happen to look at the right moment.
Inside, the transformation from caterpillar to butterfly takes roughly 10 days. When the adult emerges, the wings are soft and folded. It will hang and pump fluid into them for several hours before it is ready to fly. By the time it lifts off, the monarch butterfly lifecycle has moved from egg to adult in about a month.
The Four-Generation Story Behind Every Monarch You See This Fall
Here is the part that still stops me when I think about it carefully. The butterflies drifting over our fields right now are not the ones we watched last spring. They are fourth-generation monarchs, and understanding that is what makes the whole monarch butterfly lifecycle click into place.
Back in spring, the butterflies that left their wintering grounds in the mountain forests of central Mexico traveled thousands of miles northward, some reaching as far as Canada. As they moved, the first generation laid eggs on milkweed plants along the way. The second generation hatched, became butterflies, and continued north, repeating the process. The third generation did the same. The butterflies migrating south through our area right now, the fourth generation, are the ones that will complete the journey back to Mexico, to forests their great-grandparents left months ago. They have never been there. They find it anyway.
Telling the Male from the Female
Both sexes share the same striking orange and black pattern, but the male and female are easy to tell apart once you know what to look for.
The male has a small black dot on each hind wing, a scent patch used in courtship.
The female’s wing veins are slightly thicker and darker, giving her wings a bolder, more pronounced pattern overall.
On a calm day when one lands on a flower long enough to study, the difference is clear.
Why There Are So Far Fewer Than There Used to Be
What is difficult to sit with is how few of them remain. More than 90 percent of the monarch population in North America has disappeared in the last 20 years, according to the U.S. Fish and Wildlife Service. The causes are habitat loss and herbicide use, which eliminates milkweed, the only plant a monarch butterfly caterpillar can eat. No milkweed means the lifecycle cannot complete. It is that straightforward, and that serious.
Ranchers, farmers, and county governments all have a role in changing the trajectory. Roadside spraying with herbicides is one of the most significant and least discussed contributors to milkweed loss. I contacted our Tulsa County Commissioner not long ago and asked whether the spraying along our stretch of North Lewis Avenue could be stopped, and explained why. He agreed. That mile of roadside is no longer sprayed. It is a small thing, and it is something others in any county could ask for in their own areas.
For those of us with gardens and land, planting milkweed is the most direct contribution we can make. It does not take much space. It does not require much attention. If you are already thinking about what to put in the ground to support the wildlife on your homestead, the Integrating Wildlife Habitats in Your Homestead guide is a good place to start. What milkweed does, specifically, is give the next generation of monarchs somewhere to land and complete a lifecycle that has been running through these fields for longer than any of us have been watching it. Monarchs get the attention, but watch for tiger swallowtails on button bush in late summer. Butterflies are not the only pollinators pulling their weight — meet six common bee species. For a butterfly that survives by pretending to be something else, see the red-spotted purple butterfly.
