Build Your Own Butterfly

Every summer as a kid, my mom and I would go out in search of monarch caterpillars to bring inside and hatch into butterflies - until later, it was something I thought everyone did as a kid. Then, last summer, I found a black swallowtail caterpillar in my garden by accident or providence, almost fully grown and munching on my dill. I brought it and some dill inside, and watched it eat and eat and eat before cozying up in an unremarkable brown chrysalis that belied the truly insane shit happening within. When she successfully emerged a couple weeks later, crumpled and damp for the first hour before stretching out her wings, learning how they worked and finally using them to fly away, I felt like an incredibly accomplished wizard. Now everyone around me (including you!) is subjected to intense peer pressure to join me in the pursuit of butterfly husbandry. You too can feel like a wizard!!

Last summer's butterfly, a lady named Marguerite

I fully accept that most people would never consider enlisting their time and effort to increase the population of bugs in their house, but I think we can all agree that butterflies get a pass, insect-wise, and as experiments go, a few weeks and a bit of dill is a fairly low barrier to entry for a truly delightful payoff. If this sounds like your idea of a good time, welcome to my TED Talk. If you are a person who can't tolerate the idea of having a magical worm in your house for any amount of time, please direct your attention instead to an excellent interview with the makers of our favorite ceramic jars.

Growing up in Tennessee, monarch caterpillars were fairly easy to find, given the mild climate and availability of milkweed (their only food source). Depending on where you live, it's worth doing some investigating to find out what butterflies live in your area and where you can find their caterpillars and food sources. If you're in Colorado, black swallowtails are a good place to start.

Black swallowtail butterfly

I grew this and you can too!

Supposedly they will eat any plant in the carrot family (parsley, dill, fennel, carrots, celery, Queen Anne's lace, and rue), but I've only ever found them on or seen them eat dill and fennel. Fortunately, both are easy to grow, so that's your first step: either plant some dill plants in spring, or befriend someone who has. You want to make sure the plants you're using haven't been treated with any pesticides (even organic ones will deter butterflies and kill caterpillars); if you're local, I like Harlequin's Gardens and The Flower Bin.

Once your plants are established and growing, you may catch a butterfly in the act of laying eggs, or you may have to check your plants every few days for caterpillars. They are super duper small at first - sort of a brownish area, with points - and they'll go through five growth stages called instars before they reach full size. Here's what to expect when you're expecting butterflies:

You can bring them in at any stage (or not at all, if you wanna be a Viking about it), but the longer they stay outside the less likely they are to make it to butterflyhood - if left to their own devices, something like 98 percent of caterpillars die before metamorphosis. I set mine up in a clear enclosure in my kitchen with a few branches of dill or fennel in a cup of water covered with plastic wrap to prevent accidental drownings, on top of a paper towel for ease of cleaning (let it be known that caterpillars are just living tubes and they poop, a lot).

A first instar caterpillar on my dill outside

Apart from refreshing the dill, water and paper towel when needed, that's about it. It's easy, guys! Once they start looking like proper caterpillars (below), it's a good idea to put a clean, sturdy stick in the enclosure. When the time comes to pupate, they will unceremoniously evacuate an alarming quantity of waste, and immediately and urgently start looking for a suitable place to transform into a chrysalis. They're gonna want that stick.

A proper caterpillar, doing what it does best

Then they'll hunch up under an overhang, spin themselves a little silk harness, and stop moving. Inside their skin, the chrysalis forms, and within a couple days they will split the now useless caterpillar skin and wiggle it off, revealing the chrysalis, which will change color to match whatever it's anchored to.

For the next 12-18 days, not much will happen on the outside, but what's happening on the inside is one of the craziest things a living thing can do (and has been doing for roughly 100 million years). Inside the chrysalis, the caterpillar dissolves itself into soup. Garnishing the soup are highly-specialized cells, called imaginal discs, that the caterpillar has carried since hatching from its egg. They contain the blueprints of the new parts it will need as a butterfly - legs, antennae, compound eyes, proboscis, and thousands of microscopic, beautifully patterned wing scales, the only order of insects (including moths) to have them. The discs use the caterpillar soup to fuel the rapid cell division required to reconstitute itself into a completely different animal, now with the ability to fly, in two weeks' time. It's really something.

A close-up look at wing scales 🤯

In late June of this year, I spotted a butterfly doing her egg dance on my dill, and a week or so later, spied several promising brownish areas with points. When all was said and done, I ended up with four caterpillars, which became four chrysalises. Two and a half weeks went by, and sure enough...

Black Swallowtail butterfly and chrysalis

Wizardry.

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