For the past couple of years we’ve been bringing a few extra special black swallowtail caterpillars inside to raise “by hand”. Why do we do this? For one thing, it’s fun. For another, as I believe I’ve mentioned before, we hate see all of our black swallowtail caterpillars get eaten, and when we leave them outside, most of them end up as someone’s dinner.
Raising black swallowtail caterpillars is pretty easy. In case anyone wants to try it, I’ll boil it down into a few steps.
Step 1) Plant fennel, dill, or parsley.If you plant it, they will come. By midsummer, you should see some tiny yellow eggs. Within a few days, these will hatch and you’ll see little black and white caterpillars that look a little bit like bird poop. After a week or so, they’ll be green, yellow, and black like the guy in the picture above.
Step 2) Buy a critter cage.
Only about five bucks at Petsmart.
Step 3) Select your caterpillars.
Pick out a few nice, healthy looking individuals to bring into your cage. You can wait until they get to the black, green, and yellow stage if you want. The bird-poop camoflage keeps them pretty safe up to this point.
Step 4) Collect some food.
Feed your caterpillars using the whatever plant you collected them from. If the eggs were laid on fennel, feed them fennel. If parsley, feed them parsley, and so on. In theory, black swallowtail cats can eat all of the plants I’ve mentioned, but once they start eating a particular species, that’s the species they have to stick with.
We usually use fennel. It’s easy to grow and is easy to set up in the cage.
Step 5) Put the plant cuttings (food) into water.
We just take a small glass, fill it with water, put plastic wrap over the glass (keeps the caterpillars from drowning), poke a tiny hole in the plastic, and then insert the plant cuttings.
Step 6) Put a nice stick into your cage.
Your caterpillars will be much happier pupating on a stick than on the side of the cage.
Step 6) Put the caterpillars on the plant cuttings.
The easiest way to do this is to avoid touching the caterpillars at all. Just cut off a stem from your plant that already has one or more caterpillars on it. Be very careful touching the caterpillars. They’re very delicate and you can easily hurt them. They don’t sting, but if they get alarmed, they will spray a stinky chemical onto your hands.
Step 7) Check your caterpillars regularly.
Make sure they’re not running out of food. Make sure the plants have enough water. And clean out that cage! Caterpillars poop a lot more than you’d think. Putting a fresh paper towel down is a nice idea.
Step 
Let them go.
When butterflies emerge, let them out right away! They need food and warmth. You may want to move the pupae outside to make sure that your poor butterflies don’t have to spend a day cooped up if they emerge while you’re at work.