Meet Sedgewick the Monarch Caterpillar—and find out what you can do to save his species

Meet Sedgewick the monarch butterfly caterpillar.

Cute little fellow, isn't he?

I want to tell Sedgewick's story because it's fascinating and because his species is in real trouble and needs our help. More on that in a bit.

Sedgewick's story starts in my backyard. After living in apartments with no outdoor space to garden, my partner and I recently bought a house with a small yard. I work for the National Wildlife Federation, and so was excited to plant our very own wildlife-friendly garden. The first thing we did was pick up some milkweed plants in the hopes of attracting female monarchs looking to lay eggs.

Like all butterflies, monarchs start out life as caterpillars. After hatching from their eggs, caterpillars feed on the leaves of plants. Plants, however, are filled with chemicals that are designed to keep insects–like caterpillars–from eating them. Over hundreds of thousands of years, each butterfly species has evolved a tolerance to the toxins of just a small number of plants. These “host plants” are the only food source for any given species' caterpillars. Some species can feed on several different kinds of plants. In the case of monarchs, milkweed is the only plant they can use as a host plant.

Milkweed is the only food source for monarch caterpillars. This is a swamp milkweed (Asclepias incarnata).

Unfortunately, no female monarchs showed up to lay eggs on our milkweed plants. A few weeks later, we happened to stop by a local nursery to look for a few more plants to add to the garden. To our delight, we spotted a tiny monarch caterpillar on one of the swamp milkweed plants.

Clearly, we HAD to buy the plant and take it home with us, complete with the monarch caterpillar.

We named him Sedgewick and decided to raise him in a terrarium to keep him safe from potential predators and parasites. This is very easy to do. We got a simple plastic terrarium with a tight fitting lid, lined it with paper towels that we changed daily, and supplied Sedgewick with fresh milkweed leaves to feast upon each day.

There's one thing you need to know about caterpillars. They are eating machines. Their sole purpose in this phase of life is to eat and grow and eat and grow. And they grow very quickly. See how much bigger Sedgewick is in this photo versus the one at the top. That's just a two day difference.

Sedgewick resting on some milkweed leaves, the only food source for monarch caterpillars.

In addition to eating and growing, caterpillars poop. A lot. Food goes in one end and poop comes out the other, all day long. (Fun fact: caterpillar poop is called frass).

As the caterpillar grows, so does its frass. In this photo, you can see how much frass Sedgewick produced in just one day. You can also see how the frass grew in size. The tiny pellets are from early in the morning, and the bigger ones are from late in the evening. That's an indication of just how much he grew in one day.

Caterpillar poop is called frass and they produce a lot of it.

It takes a monarch caterpillar about two weeks to go from hatching to pupating. We "adopted" Sedgewick a couple of days into this process, so for the better part of a week and half, he ate and grew.

This photo shows Sedgewick at about 12 days old, just before he began to pupate. Again, compare this picture to the ones above to see how dramatically these caterpillars change in size.

Then, one morning, it happened. We went outside to clean out the frass at the bottom of Sedgewick's terrarium and to resupply him with fresh milkweed leaves. On this particular morning, he wasn't hanging out on the stick where he normally spent the night. We found him hanging from his hind end on the bottom side of the terrarium lid, curling his body into a "J" shape.

This is the first stage of pupation, where a caterpillar forms a chrysalis and radically alters its physical shape and turns into an adult butterfly. (Fun fact #2: Moth caterpillars don't form a chrysalis, but instead spin a silken cocoon in which they complete metamorphosis.)

Sedgewick in the "J" shape preparing to form a chrysalis.

By the time we got home from work, all that was left of Sedgewick the caterpillar was his old skin, left in a crumbled heap on the bottom of the terrarium floor.

In his place was this gorgeous green chrysalis.

Sedgewick formed his chrysalis about fourteen days after hatching out of the egg.

What happens inside of a chrysalis is almost magical. A plump, wormlike creature will change its form into a glorious, brightly-winged beauty. Just as the caterpillar phase lasts about two weeks, so it takes around another two weeks for a pupa to complete this metamorphosis.

The chrysalis phase is much less dramatic than the caterpillar phase, at least on the surface. A chrysalis doesn't move or need to eat. But that doesn't mean it's dormant. Radical change is happening.

Inside the chrysalis, the body of the caterpillar essentially liquifies and reforms itself into the body of a butterfly. It's almost like something out of a science fiction story. Except it's not fiction.

There is some external change in the chrysalis too, it's just subtle. At first, the chrysalis is semi-transparent, and you can see the shape of the changing caterpillar within. After a few days, however, it turns a lovely opaque sea-foam green with metallic gold dots.

Sedgewick chrysalis 2
Sedgewick's chrysalis was a beautiful green with gold flecks.

When the transformation from caterpillar to butterfly is almost complete, the chrysalis begins to rapidly change in appearance.

As the emergence nears, the chrysalis turns dark. When that happens, the butterfly will emerge within the next several hours. You know emergence is imminent when the walls of the chrysalis go totally transparent, and you can see the folded up butterfly inside.

These two photos were taken about an hour apart:

Sedgewick emerges as a fully-formed adult monarch butterfly.

Once the butterfly has emerged, it spends some time flexing its wings to pump fluids into them so it will be able to fly. Butterflies are ectothermic ("cold-blooded") which means their body temperature is dictated by the surrounding air temperature. If it's cooler than around 65 degrees, butterflies are lethargic and won't fly.

Since it was getting chilly in the late afternoon when he emerged, and monarchs don't need to feed for the first day or so after emerging, we kept Sedgewick the butterfly in his terrarium overnight.

Now's the time to point out that while we called Sedgewick a "he" we had no idea what the actual sex of the animal was. There's really no way to sex a caterpillar with the naked eye.

That's not the case with adult monarchs. Take a look at Sedgewick's hind wings. See the black dot on each one? That means we guessed correctly and Sedgewick is indeed a male. Female monarchs do not have that black dot on their wings.

Sedgewick explores his terrarium, shortly after emerging from his chrysalis. The black spots on his hind wings indicate that he is male.

Now we're coming to the end of Sedgewick's tale–at least the part of it that involves us.

Before we get to the video of his release into the wild, I need to take a minute to talk about the plight of the monarch. These iconic black and orange butterflies are beloved of gardeners and wildlife watchers all across North America. Sadly, those days could be over if we don’t act quickly.

Monarch populations are at a dangerous low. That decline is in large part because milkweed is becoming harder and harder to find. Industrial agriculture is increasingly using GMO crops created to be resistant to herbicides. As a result, more herbicides are being sprayed and the milkweed that once grew on the edges of millions of acres of cropland are being wiped out. That, combined with ever-growing suburbia that favors lawns and exotic plants over milkweed and other native plants, has resulted in a situation where monarchs can’t find anywhere to lay their eggs.

The good news is that there’s a really simple way to make a difference for monarchs: plant milkweed.

I repeat: PLANT MILKWEED!

There are several dozen species of milkweed native to North America, many of which are highly ornamental and readily available in the nursery trade–from bright orange butterflyweed (Asclepias tuberosa) to tall, pink-blossomed swamp milkweed (A. incarnata) and showy milkweed (A. speciosa), to the drought tolerant desert milkweed (A. subulata). And many others.

Fall and spring are generally the best times to plant, but you can plant milkweed at almost any time of the year that the ground isn't frozen.

Milkweed is easy to grow and has a lot of benefit to wildlife other than just monarchs. Its flowers are a great source of nectar for adult monarchs and many other pollinators. Milkweed seeds have a tuft of cottony fluff that allows them to drift on the wind and disperse away from the parent plant, and that tuft is often used by birds as a nesting material. Most importantly, milkweed is the only host plant that monarch caterpillars like Sedgewick can feed upon.

I collected some seeds from the swamp milkweed in my garden and plan on germinating them indoors this winter and then planting them all over the place in the spring.

Swamp milkweed seeds are easy to collect and germinate.

The moral of the story is this: no milkweed means no monarchs, so do your part and plant milkweed. Plant it in your yard. Plant it in pots on your apartment balcony. Plant it at your church, at your office, at your kids' schools.

There are few more amazing feelings than knowing that a simple act of planting a flower can make a critical difference to the survival of an entire species of butterfly.

Perhaps the only thing that feels better is getting to release a wild animal back into the wild where it belongs. So, without further ado, here is a video of Sedgewick's release.

Now, Sedgewick is on his way down to Mexico. Monarchs are one of the few migratory insects. West of the Rockies they gather in scattered locations in central California. East of the Rockies, every single monarch from southern Canada down to the Deep South migrates to just a few spots in the mountains outside of Mexico City.

They'll hang out there in high numbers in the trees and wait out the winter. Come late February or early March, they'll start the journey north. They'll get as far as mid-Texas, where they'll mate, lay eggs on milkweed and die, leaving it to the next four generations to fill in the rest of the continent over the spring and summer.

I marvel at the almost miraculous transformation monarchs undergo and incredible distances these tiny creatures travel. Let's all do are part to make sure that Sedgewick's children, grandchildren and great-grandchildren have something to eat next spring. Plant milkweed.

Happy journey, Sedgewick!

Sedgewick takes a sip of nectar before embarking on his long migration to Mexico.