How to raise caterpillars into butterflies (for fun and profit?)

As you may know, in 2020 I took up the surely common pandemic hobby of raising insects. You all did that too, right?.. Right? :cricket::cricket::cricket: Well anyway, it was great, and I’m doing it again now in 2021. I was part of a recent butterfly raising workshop, and I hope to do that again in the future, one day even in-person. :scream: But until then I thought I could share a quick overview of the process and stages, until I can write up a more detailed how-to (which I hope to do!).

Fortunately it’s pretty easy! The simplest ones to to find and raise where I live (in the East Bay, California) are Anise Swallowtails, because they lay their eggs on the wild fennel that is plentiful (or sometimes on your back yard dill plant, where I first discovered them in 2020). Look for little milky white or light brown eggs, very small, about the size of a poppy seed. Hard to spot at first but once you know what to look for you’ll find 'em. Pluck off a piece of the plant with an egg and bring it home and put the stem in water to keep the plant cutting alive.

Wait a few days, the egg will turn darker, and then a tiny, tiny caterpillar will emerge, black with a white “saddle” pattern. It will look like this:

Keep feeding it fennel (and put some newspaper or a box under it to catch its little balls of poop called “frass”), and it’ll grow bigger and bigger, shedding its skin numerous times and eventually changing its colors entirely. Like this:

They typically eat the skins they shed. Extra nutrition, mm!

Once it gets rather large, it will stop eating, get rid of its final partially digested meal (bright green and liquidy, unlike its typical hard little leavings), and start wandering looking for a place to pupate. It wants a sturdy, vertical or steeply angled surface to sew a little “hammock” thread onto (you can see it in the pupae close-up above). I use sticks and keep them in a closed jar during this time so they don’t wander around my house.

Eventually they should settle down and start pupating. They’ll anchor themselves, make the silk line (a fascinating process to watch!), and then grow very still until they pupate, shedding their skin a penultimate time, losing all their legs and familiar external features. A week or so later the butterfly will emerge! You’ll know it’s almost time because the pupae will grow a bit more transparent and you can usually see the wing through it, as in this photo:

It’s important that the butterfly have something to hold onto when it emerges, and it wants to keep itself basically vertical so it can properly inflate its wings. And of course it should be put outside once it emerges so it can fly away when it is ready. It takes 2-4hrs in my experience, and until then, they’re quite slow and clumsy. But they’re real pretty:

That’s it! If you have any questions, post 'em below. And I’ll be working to expand this over time with more info about things to be aware of, what can go wrong, and how to avoid a caterpillar pupating on your curtains.