Metamorphosis – a Caterpillar Becomes a Swallowtail Butterfly

Dilly the swallowtail caterpillar leans back and begins his transformation into a chrysalis. Photo © Diana Pappas

Dilly the swallowtail caterpillar leans back and begins his transformation into a chrysalis.
Photo © Diana Pappas

[ This is Part Two of the story of Dilly the swallowtail – if you have not yet read Part One, please do so by clicking here! ]

When Dilly, the swallowtail caterpillar we accidentally welcomed into our home, fastened his safety harness, scrunched himself up and let go of the dried lily stem he chose as the site for his transformation, we really had no idea what would come next. You’d naturally assume that he’d spin a cocoon or something – but cocoons are for moths. A swallowtail caterpillar needs to make a chrysalis in order to become a butterfly. If we hadn’t seen it happen with our own eyes we’d have been incredulous at just how a caterpillar becomes a chrysalis. Just two hours after Dilly the caterpillar had leaned back and seemingly settled in (see photo, above), Tom was in the kitchen and yelled for me to come quick.

Imagine for a second getting out of a skin-tight wetsuit without the use of your arms or legs – that is essentially what Dilly was doing as he jerked this way and that, stretching the thin silk threads that kept him suspended on the lily stem as he violently swung his body about and in so doing, shed his stripy caterpillar skin to reveal, underneath, a green chrysalis. It took a matter of seconds!

The black swallowtail caterpillar sheds its striped skin by violently jerking its body side to side, revealing a chrysalis underneath. Photos © Diana Pappas

The swallowtail caterpillar sheds its striped skin by violently jerking its body side to side, revealing a chrysalis underneath.
Photos © Diana Pappas

Once the skin was shed and dropped to the bottom of the terrarium, Dilly settled down and stayed motionless. His camouflage was impressive, he easily looked like a green leaf. Over the course of the night and the next day he leaned back further and further, arching his back, the silk threads cutting into his side a little bit but supporting him perfectly. Wow!

The swallowtail chrysalis. Photo © Diana Pappas

The swallowtail chrysalis.
Photo © Diana Pappas

It had been easy enough to ply a caterpillar with his favorite foods – dill (obviously) and parsley, carrot, fennel and cilantro leaves and flowers. It had been easy to tell at a glance what was his current state – he was either eating or resting or pooping or moving. But when a caterpillar becomes a chrysalis, you, the observer, become excluded from the front row view. Questions came up. “When is he going to come out?” “What color will he be?” “What is happening in there?” “Are those horns!?” “Is he alive?” We needed to have faith that nature knows what it’s doing and if all variables were favorable, Dilly would emerge alive, those “horns” would become antennas, wings would develop, and a swallowtail butterfly, either black or yellow in color would be before us. It’s easy to see why the word “magic” is often referenced in the metamorphosis that takes place from chrysalis to butterfly – you can’t see it happen, you can’t imagine how it happens, but it happens! We were excited.

We knew the period of time spent in the chrysalis could be as few as 9 days or perhaps 2 weeks, but towards the end of summer, swallowtail caterpillars were known to take their time and overwinter as chrysalises! That’s a long time to have a houseguest. Luckily the flowers are still in bloom here with plenty of nectar for an emerging butterfly, so I was pretty confident there was no reason he shouldn’t emerge in a relatively short amount of time. So we’d check in on Dilly every few hours, but after the excitement of watching a caterpillar swell in size, the chrysalis stage was a bit of a yawn. Even though it was varying shades of green and yellow and had an almost reptilian pattern to it, the chrysalis looked the same every day.

My imagined plan for Dilly’s emergence was pretty nice I must say. I was going to wake up and see some movement and grab the camera to witness him break through the chrysalis with shriveled up wings close to his body. I’d take my time getting detailed macro photos and Dilly would take his time sending liquid to his shriveled wings so that they would extend to their full glory. It would take him about 4 hours to dry his wings and pump them to be ready for flight and once this happened I’d extend him a finger, he’d climb on, and I’d set him right on our purple butterfly bush (Buddleia) for his first meal. We’d take some more pictures, and then I’d shed a tear as he flew off on his first flight to sample the phlox or the rose of sharon blooms, or maybe go check out the zinnias. A good plan, right?

The reality was of course, very different. This morning, a little bleary eyed and not yet woken up with a cup of tea, I went in to check on Dilly as usual. I could tell from 10 feet away that the chrysalis looked a little different. The bottom quarter of it was darker and the shape looked odd. I called out to Tom, “I think Dilly is going to come out today!” And then, I looked closer.

The chrysalis was hollow and there was a butterfly at the bottom of the terrarium.

Not only was there a butterfly at the bottom of the terrarium, he was black in color, and more important than that he was alive, with his wings fully extended, and he looked ready to get out of there!

Dilly, a male black swallowtail butterfly in a terrarium, having just emerged from his chrysalis earlier in the day.

Dilly, a male black swallowtail butterfly in a terrarium, having just emerged from his chrysalis earlier in the day.
Photo © Diana Pappas

Dilly climbing on a sheet of paper towel lining the terrarium, ready to fly away.

Dilly climbing on a sheet of paper towel lining the terrarium.
Photo © Diana Pappas

My imagined plan had to be quickly abandoned and after a few clicks we realized we just had to get him outside as soon as possible. He was ready and who knows how long he had been ready and waiting! I carried the terrarium outside, Tom grabbed the camera, and right next to the butterfly bush I removed the netting, and lowered a finger in to give him a lift as I had so idealistically imagined. He set a foot on my finger, and then decided to go his own way. He flew out and up and deftly made his way across the sunlit yard. He perched for a moment or two, and then took off again and went out of sight.

Dilly, a beautiful male black swallowtail butterfly, perched in the sun in our backyard having just emerged from his chrysalis earlier in the morning.  Photo © Tom Bland

Dilly, a beautiful male black swallowtail butterfly, perched in the sun in our backyard having just emerged from his chrysalis earlier in the morning.
Photo © Tom Bland

I wish I could have reveled in the details, the spots on his body, the many colors on his wings, the curl of his tongue, the delicate long legs and antennas, the little fuzzy hairs, the gloss and sheen of his eyes, but it all happened so quickly! If only we had woken up earlier, I thought. In the end, Dilly didn’t belong to us, did he? We fed him and protected him and housed him, but he was on his own schedule and wouldn’t accommodate ours. Now that he’s on his own and flying around I can’t help but worry about his safety, that he’ll find good nectar sources, that he’ll find a female, that the weather will be favorable and that he’ll escape any kind of predation, but of course it is out of my hands.

The empty chrysalis. Photo © Diana Pappas

The empty chrysalis.
Photo © Diana Pappas

It’s a relief though, and we have a great sense of accomplishment too, that he was able to safely make the transition from tiny caterpillar to big caterpillar to chrysalis to butterfly before our eyes. We have learnt an enormous amount in witnessing this process, and on a personal note I feel grateful to this little creature because in getting to know him I was able to finally shed my fear of caterpillars. There are a couple of swallowtail caterpillars on our flowering parsley in the garden right now, and instead of recoiling when I see them, I get close and watch them, fascinated.

Two swallowtail caterpillars on parsley plants in the garden. Photo © Diana Pappas

Two swallowtail caterpillars on parsley plants in the garden.
Photo © Diana Pappas

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3 responses to “Metamorphosis – a Caterpillar Becomes a Swallowtail Butterfly

    • Thanks Marina! I’d love to do a guest blog post on BookSprout, thanks for the invitation! Curious children of all ages have so much to learn from this project – there’s even a emotional lesson to be learned from saying goodbye. I miss Dilly!

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