Once the female Black swallowtail lays eggs, and they hatch, the caterpillar will go through 5 instars in about 4 to 10 days, changing colors and getting rows of yellow spots and green stripes to help it blend with the environment.
Black Swallowtail Life Cycle Overview and Timeline
After Black swallowtail eggs hatch after about 4 to 10 days, this butterfly will have 5 instar stages, lasting for 3 to 4 weeks. The first instar will have a “saddle” marking — a white spot in the middle of its black/brown body.
As it grows to the second, third, and fourth instar, its yellow spots and black bands will get larger, and white markings and green stripes will help it camouflage better.
Finally, it will reach the fifth instar with a green shade and yellow and black spots. It will become smooth. A full-grown larva has an orange horn-like gland on its head (osmeterium).
This color combination and the patterns make it quite difficult for the predators (wasps) to spot. After these instars, the caterpillar molts and pupates for around 10 to 14 days. During this time, they look like dark-colored bird droppings.
How Long Does It Take for a Black Swallowtail Caterpillar to Turn Into a Butterfly?
On average, the entire process from Black swallowtail egg to butterfly takes more than a month (sometimes longer when the pupa goes into the overwintering phase).
The caterpillar develops into a pupa within 3 to 4 weeks, and a fine silk thread holds the Black Swallowtail chrysalis to the host plant. An adult Black Swallowtail butterfly emerges in another 10 to 20 days. Right before the adult butterfly emerges, the chrysalis will turn clear.
How Do You Know When a Swallowtail Caterpillar Is Ready to Cocoon?
Swallowtail caterpillars are ready to cocoon when they reach their fifth and final instar. At this stage, they are black, white, and green striped and around 2 to 3 inches in length. It will stop eating and focus on placing itself in the best spot to pupate.
Where Do Black Swallowtails Make Their Chrysalis?
The caterpillars enter the “wandering” phase towards the end of the fifth instar. During this period, the larva goes as far away from its host plant as it can. It is looking for a secure location to create the chrysalis and avoid predators while it’s vulnerable.
Once the larva has chosen the perfect plant, the Black swallowtail caterpillar creates its chrysalis and attaches one of the ends to a nearby twig or branch. The silk thread will “glue” it to the plant, reducing its movement. The usual host plant in golden Alexander.
What Do Black Swallowtails Eat Before They Pupate?
Caterpillars need to store energy, so they have fuel that their bodies will use to undergo metamorphosis. They store energy before they get to the pupal stage. This is why caterpillars will constantly feed on host plants:
- Carrot tops
This stored energy helps sustain butterflies for a significant part of their adulthood and, sometimes, even toward the end of their life cycle.
What Is the Black Swallowtail’s Natural Habitat?
The Eastern black swallowtail can be found throughout North America, and South America. The Black swallowtail and its caterpillars live around the following butterfly habitats:
- Open fields
The Best Host Plants for Black Swallowtail Caterpillars
Some of the best host plants you’ll want in your butterfly garden are plants from the carrot family (Apiaceae), such as Queen Anne’s lace and:
- Butterfly weed
Other key plants for Black swallowtails are dill, fennel, parsley, and coneflowers. These plants are the ideal spot for these beautiful butterflies to lay eggs.
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Joan is a nocturnal person who loves traveling and coffee. She’s also an animal lover (and rescuer) who makes it a point to befriend every animal she meets. Her passion for learning led her to writing about various topics. As someone who is a nature lover, she aims to continue learning about the wonderful creation—especially butterflies, and at the same time, share her knowledge here at Butterfly Hobbyist.