The black swallowtail is a favorite of birds for food. I have made cages out of plastic snack containers (gallon size or larger) by cleaning it out well, then cutting sections out of the sides to adhere screen material (I use clear bathroom caulk to act as a glue) to the cut out sections covered with screen to allow for air flow. Then I place a paper towel in the bottom and bring in stems of their host food for them to feed on. This protects the caterpillars from predators and give them a better chance at reaching butterfly stage. Not all cats make it to adulthood, but their chances are better with the protective help. Then be sure to sterilize your cage after all the chrysalids have emerged. BSTs may overwinter as a chrysalis. I have had some stay in chrysalis for over a year and still emerge as healthy butterflies the following spring or summer.

In the "wild" only 2 or 3 eggs out of 100 make it to adult butterfly stage. The caterpillar can travel some distance to become a chrysalis. The BST prefers to find a stick or twig (or vertical surface) that they can attach to in an upright position. Hope this helps you decide what to do about the remaining cats you have been observing. Best of luck to you!

Mechelle

Hi Debra! Congratulations to you on the Black Swallowtail caterpillars. They are gorgeous caterpillars that turn into awesome looking butterflies. Thank you for caring enough to want to keep them safe. Mechelle made some good points already. There are many types of containers which can successfully be used to raise the caterpillars to adult butterflies. It is such a wonderful blessing to be able to observe the process each step of the way. If you Google "caterpillar rearing containers" and look at images, you will see the various types that people use. There are many wild creatures which eat butterfly eggs, caterpillars, and also chrysalides. Bringing them in to a safe place to develop is great for them and for you too. Yes, if they were not eaten by something, the large ones probably crawled off somewhere in order to pupate. ~~Angie

I would collect your caterpillars and put them in a container to raise. Black swallowtails are relatively easy caterpillars to raise and they have adapted to an assortment of host plants that are easy to grow. Plus they are kind of lazy caterpillars that tend to just hang out and eat.

I raise them in large salad boxes, and grow Rue, Parsley, Dill, Bronze fennel, and Zizia for their larval host plants. I like to make little herbal bouquets for them to munch on.

I've got 4 BSTs that just formed chrysalises in the past few days. I'm hoping they all eclose, and go off to populate the countryside, but some of them overwinter each year and then eclose the next Spring, usually in May.

Thank you everyone for the wonderful advice. I brought them inside last evening after I spotted a Robin watching the herb garden. I just clipped off the dill stems they were eating on, so not too much trauma for them. I put them in a tall plastic container with a piece of fibreglass window screen rubber banded for a lid.
I have plenty of parsley and fennel to feed them. I can see that this can become quite an interesting hobby/habit.
I have found lots of good information on what to expect as they grow larger, and get ready to pupate.
I will keep you updated on the progress.
Thanks again, Debra

You are welcome Debra! Yes, it becomes addicting very quickly. They must shed their skin in order to grow, and when it is time for a molt, the cats will become very still and stop eating for a bit. Don't be concerned. Also note that they will "purge" their bodies just prior to pupation. So, you will see what looks like a pile of diarrhea inside the container. They like to attach themselves to small sticks, so when you have big caterpillars, you might want to angle a couple of sticks inside the container. Here is a pic of an attached cat and one that has pupated. The chrysalides can be green or brown. Good luck, and keep us posted!~~Angie

Great to hear you brought some inside! BSTs are a great caterpillars to raise.

I have had a hard time getting parsley going this year - started a few seedlings in Spring, then fried them when I put them out in the veggie garden and forgot to water them. Bought a 6-pack of what I thought was parsley at the nursery a few weeks ago, turns out is was celery (it looks a lot like flat parsley!). Finally headed out on July 4th to try again, and a local farm was having a sale on annuals and they had some great parsley, dill and fennel (and they said they do not spray and I believe them, it's a Mom & Pop place).

I just had to check the plants for eggs. In addition to a couple 6 packs of parsley and 1 fennel plant, I came home with 10 new eggs! 3 have already hatched. Yippee!

Terrene,

Congrats on the new cats and eggs! That is always the best bargain, finding eggs/cats on plants you are going to purchase anyway. Keep us posted.

Mechelle