Day 15: Pupation

Yes, that’s actually a word.

As I mentioned a few days ago, I raise caterpillars. I had two caterpillars that were growing well when the one in that post drowned, but later that day the other one began the process of turning into a pupa, which is the stage where its insides dissolve and re-assemble into an adult butterfly. And I was l fortunate enough to record video of that happening.

Some moths spin a cocoon of silk to encase themselves while they transform, but butterflies do not. Instead, they simply shed their skin. I say “simply”, but it’s pretty amazing.

As caterpillars hatch, they go through several stages, or instars, as they grow. At each of these stages, they shed their old skin to reveal a newer, bigger skin underneath, and each stage looks different than the others.

Black Swallowtail stages from caterpillar to butterfly
Eastern Black Swallowtail stages of development

Once the caterpillars have grown enough, they stop eating, and attach their tail end to a branch or other surface, and spin a sling of silk to hold them in place (see the “pre-pupa” in the image above). Over several hours the caterpillar just seems to be hanging out there, but there is a lot going on.

First, its body is detaching itself from its legs. It’s also sealing off its mouth and rectum. Then it begins forming a relatively tough, solid layer of skin underneath its existing skin. Once that skin is complete, the caterpillar begins to pulsate and wriggle, finally splitting its old skin and then shimmying its way out of it.

So when the caterpillar attached itself yesterday, I set up my phone’s camera to time-lapse, and left it running for several hours. The video is really amazing to watch.

If all goes well, this little guy will remain as a pupa for around 2 weeks, and then it will crack open that chrysalis, and emerge as a beautiful adult butterfly. I’ll be sure to post about that when it happens!

2 thoughts on “Day 15: Pupation”

  1. We’re growing the same, but ours are emerging after about four days. I was going to suggest colder climate, but aren’t you in SATX?

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