Black Swallowtail Butterfly: Caterpillar to Newly Emerged Butterfly

September 27, 2023

Earlier this summer, I added two more fennel plants in my butterfly garden as the last couple of years the Eastern black swallowtail caterpillars having been eating up my one fennel plant. This butterfly loves fennel, dill, parsley, Queen Anne’s Lace, and carrot tops for their host plants.

The butterfly season has been late getting started this year with activity in my garden. Finally, in August I started seeing a female Eastern black swallowtail butterfly hovering over the established fennel plant then go nectaring on nearby plants. Of course, this is the action of the female swallowtail laying her eggs on the fennel.

I did check to see if I or my spouse could find any of the Eastern black swallowtail eggs on the fennel. However, I have yet to be able to find an egg of this butterfly species. Their eggs are very tiny, spherical and slightly yellow to cream color. The female black swallowtail butterfly will lay their eggs singly as they glue the eggs to the leaf of the plant. Although they lay eggs singly, there may be many eggs on one host plant.

Black Swallowtail Caterpillars

Just a couple days later, I checked the fennel plant again, and there were about a dozen or more of black swallowtail caterpillars crawling or slowly eating on the plant. These caterpillars were mainly in the first or second stages which are called instars. There are five instars for the black swallowtail caterpillar before the metamorphosis begins of forming a chrysalis and then emerging as a butterfly.

The Eastern black swallowtail caterpillars undergo a very noticeable change in their appearance from the 1st and 2nd Instars to the 4th and 5th Instars. During the first two instar stages the caterpillar looks or mimics bird poop as it is their way of camouflaging in their environment. In these first two instars, the dark caterpillars will have a whitish spot of the middle of their body, just like bird droppings.

As the caterpillars develop into the 3rd instar they will start to show some orange coloring along the bottoms of the spikes they develop on their body. In the last two instars, the black swallowtail caterpillars look totally different as their bodies have turned green with black bands. In the 4th instar stage the caterpillar is yellowish green with black bands and orange spots. As the caterpillar enters its 5th instar the body will molt into a green and black striped caterpillar with orange dots along the black stripes.

Also, the 5th instar Eastern black swallowtail caterpillar will start to eat much more than the other instar stages as it gets ready to form into a chrysalis. Usually, these caterpillars will leave the host plant to find a good place to pupate such as another plant or a stick. Once the chrysalis is formed, it will take one to two weeks before, through metamorphosis, the chrysalis emerges as an adult butterfly.

Black Swallowtail Chrysalises

For the past couple of years, since I created my backyard butterfly garden, I have been unable to find or locate any chrysalises of black swallowtail butterflies. Each year, I have had plenty of black swallowtail caterpillars eating on my fennel but no chrysalises. I think the caterpillars leave my garden and yard to chrysalis in a neighbor’s yard.

This year, I just happen to be given some sprigs of herbs that include parsley, basil and chives that my mother-in-law brought me when she noticed three black swallowtail caterpillars on the parsley. These sprigs of herbs were being stored in a small container with water. Since these were not plants with roots and were just sprigs that were intended to be eaten, I decided to keep the container of the herbs with the caterpillars in my house.

Fortunately, I had a mesh butterfly enclosure on hand and put the container of herbs with the three black swallowtail caterpillars inside the butterfly enclosure. My spouse and I cut some fennel from the garden to supplement the small amount of parsley. Also, we put several twigs in the container so the caterpillars had some where to form their chrysalises as they prefer to do so on twigs or sticks.

Each day, my spouse or I would check on the caterpillars which were in their 4th instar stage when we received them. I was excited to be able to finally witness and photograph the black swallowtail metamorphosis into a beautiful butterfly. Once all three caterpillars were in their chrysalis state, we carefully removed the container with the sprigs of herbs and twigs from the butterfly enclosure. Two of the caterpillars actually used dried fennel stems to make their chrysalises, while the third one used a brown twig from a tree.

The first chrysalis was in that state for almost two weeks before the black swallowtail butterfly emerged from the chrysalis. The second chrysalis to form was in that state just shy of two weeks, while the third chrysalis took just over a week before emerging. Over Labor Day weekend, all three butterflies emerged from their chrysalises.

Just before, the butterfly emerges, the chrysalis turns black. With all three of these chrysalises, the time between the chrysalis turning black and the butterfly emerging was a short time. Two of three butterflies emerged in the mornings of Saturday and Sunday of Labor Day weekend, while the third butterfly emerged on Sunday afternoon. Just like that, all three of my little buddies had gone through their pupa state and were released.

Once a butterfly emerges from its chrysalis, it takes an hour or two before their wings are dry and they are able to fly off. So, for each of the three butterflies, I was able to photograph them just after emerging from the chrysalis. Once each of the butterflies emerged, I would photograph them for only about thirty minutes before we took the the twig or fennel stem with the butterfly hanging on it outside so the butterfly would be able to fly away and nectar up. Unfortunately, they emerged from the chrysalis very quickly, and I never got to photograph or observe that action.

In photographing the chrysalises and the emerging butterflies, for some of the images I used a solid color background far away from the subjects so that I would not have the clutter of a bookcase, window or fireplace, etc., in my background. I really liked how some of these images turned out and am grateful to have experienced and watched this wonderful transformation in the development of these beautiful butterflies.

Thank you to my mother-in-law, Louise, for entrusting these three black swallowtail caterpillars into our care.

I am proud that the three caterpillars turned into three magnificent butterflies that are now on their life’s journey.

Thank you for reading my Field Notes Blog, and I hope you will share this post with others.

Let’s preserve and conserve our natural world.

All the best,

Lori

Copyright © 2023 Lori A Cash Conservation Photography, LLC