Black Swallowtail Butterfly Facts: Quick & Intriguing Insights

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The black swallowtail butterfly, scientifically known as Papilio polyxenes, is a majestic and fascinating creature.

Known for its distinctive black and yellow markings, these butterflies are commonly found in North America gracing gardens and meadows.

One remarkable feature of the black swallowtail butterfly is its extraordinary life cycle, which includes four stages – egg, larva, pupa, and adult.

As they grow, their appearance changes dramatically, and they display remarkable adaptability.

For those seeking to attract these beautiful creatures to their gardens, planting their favorite host plants such as parsley, dill, or fennel will make them feel right at home.

Black Swallowtail Butterfly Facts

Black Swallowtail Butterfly Facts

Species and Classification

The Black Swallowtail (Papilio polyxenes) is a species of swallowtail butterfly belonging to the Papilionidae family.

Its other names include the American Swallowtail and Eastern Black Swallowtail. Native to North America, their habitat ranges from Alabama to Wisconsin, and areas in between.

Physical Appearance

The Black Swallowtail butterfly exhibits sexual dimorphism, with differences in color and size between males and females:

  • Males:

    • Wingspan: 2½ – 3½ inches (6.7 – 8.9 cm)
    • Predominant bright yellow band on wings
    • Row of yellow dots and dashes on wing borders
  • Females:

    • Wingspan: 3¼ – 4¼ inches
    • May lack bright yellow band or display it minimally

Female Black Swallowtail

Comparison Table

Wingspan2½ – 3½ inches (6.7 – 8.9 cm)3¼ – 4¼ inches
Yellow Band on WingsProminentMinimal or absent
Yellow Dots and DashesPresentPresent

These beautiful butterflies can mostly be found in open areas, such as fields, meadows, parks, wetlands, prairies, and sunny backyards.

Distribution and Habitat

Range in North America

The black swallowtail butterfly, scientifically known as Papilio polyxenes, is native to North America.

This species is widely distributed across the eastern and central parts of the continent, extending from the Rocky Mountains to the eastern coast1.

Preferred Habitats

Black swallowtails have a preference for open areas that receive ample sunlight. Examples of these habitats include:

  • Fields
  • Meadows
  • Parks
  • Wetlands
  • Prairies

In addition, they can be found in marshes and sunny backyards2. It is essential for their habitat to contain host plants, such as parsleys and fennel, which are vital for their larval development.

Female Black Swallowtail Butterfly

Lifecycle and Growth Phases


Black swallowtail butterflies lay tiny, spherical eggs on host plants such as parsley, dill, or fennel. These eggs are:

  • Creamy white
  • Develop a darkish band near hatching

Some eggs get preyed upon by parasitoids or birds.


When the eggs hatch, the caterpillars emerge. These caterpillars, or larvae, have:

  • Bird-dropping appearance (early instars)
  • Green with black bands (later instars)

Caterpillars transition through 4-5 stages called instars. They feed on the host plants, growing quickly and eventually shedding their skin.

Black Swallowtail Caterpillar


The caterpillar forms a pupa, or chrysalis. Pupae are:

  • Green or brown
  • Suspended from stems or leaves

During this phase, their body undergoes a significant transformation. In warm climates, this transformation may take only 10-15 days.

Adult Butterfly

Finally, the adult black swallowtail butterfly emerges. Adult features include:

  • Wingspan of 2½ – 4¼ inches
  • Black with yellow spots (males)
  • Black, often with a lesser amount of yellow (females)

Adult black swallowtails live for about 12 days. They seek out nectar-rich flowers and mate, beginning the cycle anew.

Black Swallowtail Emerges from Chrysalis

Diet and Feeding Behavior

Host Plants for Larvae

Caterpillars of the black swallowtail butterfly, Papilio polyxenes, feed on a variety of plants in the carrot family (Apiaceae) including:

  • Fennel: An aromatic herb often used in cooking
  • Parsley: A popular herb rich in vitamins and minerals
  • Dill: A flavorful herb with feathery leaves
  • Celery: A crunchy vegetable high in fiber
  • Caraway: A plant producing seeds for culinary use
  • Queen Anne’s Lace: Also known as wild carrot or Daucus carota
  • Spotted water hemlock: A toxic plant that should be avoided1

Larvae avoid feeding on milkweed and clover. Becoming vivid green caterpillars with narrow black bands on each body segment, these bands are interrupted by yellow-orange dots2.

Nectar Sources for Adults

Black swallowtail butterflies enjoy nectar from a variety of flowers, focusing on the following:

  • Milkweed: A group of plants with milky sap and clustered flowers
  • Clover: Small flowering plants in the legume family
  • Spotted water hemlock: Despite its toxicity for caterpillars, adult butterflies feed on its nectar

These sources provide the energy and nutrients needed for reproduction and migration.

Black Swallowtail

Survival Strategies

Predators and Defense Mechanisms

Black swallowtail butterflies have several ways to fend off predators. One of their primary defense mechanisms is their appearance, which features bright yellow spots on the wings and often mimics harmful butterflies known for their toxins.

This is called Batesian mimicry of another, more toxic swallowtail butterfly. The bright markings can potentially deter predators.

Another defense mechanism is their osmeterium, a specialized organ found in their head. When threatened, the caterpillar can protrude the osmeterium, which releases a foul-smelling chemical to deter predators.

Comparison Table

Defense MechanismDetails
Batesian MimicryMimics the appearance of harmful, toxic butterflies to deter predators.
OsmeteriumA special organ that produces a foul-smelling chemical for defense against predators.

Impact of Habitat and Human Interaction

The habitat of black swallowtails is generally open areas, such as fields, meadows, parks, wetlands, prairies, and sunny backyards.

They have a wingspan of 3-4 inches with a distinct tail on their hindwings. This tail is not required for flight and can be sacrificed to escape predation.

Human interaction can both positively and negatively impact black swallowtail butterflies. Gardens that offer host plants like parsley and dill can provide a beneficial habitat where black swallowtails can lay their eggs.

Conversely, the widespread use of pesticides and the destruction of their natural habitats can significantly reduce their population.

Identification and Unique Characteristics

Coloration and Patterns

Black swallowtail butterflies are notable for their vibrant colors and patterns. Some key features include:

  • Predominant combination of yellow, black, orange, blue, and red colors3
  • Rows of yellow spots along the edges of their hindwings and forewings4

These colors and patterns not only make the black swallowtail visually striking, but they also have a role in their survival, such as in mating and camouflage.

Cultural and Historical Significance

Symbolism and State Butterfly Status

Black swallowtail butterflies, or Papilio polyxenes, carry significant symbolism in various cultures. For example, they are often associated with transformation and metamorphosis due to their lifecycle from caterpillar to adult butterfly.

They are also admired for their beauty, grace, and elegance, which make them symbols of freedom, joy, and nature’s grand design.

In the United States, the black swallowtail has gained recognition as a state butterfly. It is designated as the state butterfly of Oklahoma, representing the region’s rich fauna and natural beauty.

Parsley Worm or Black Swallowtail Caterpillar

Interaction with Native Plants

Black swallowtails, also known as parsley worms or parsnip swallowtails, have co-evolved with native plants in their habitats.

They are commonly found from southern Canada, throughout the United States, and into Mexico. In particular, they have a strong affinity towards plants belonging to the family Umbelliferae, such as:

  • Parsley
  • Carrot
  • Parsnip

These plants act as primary hosts for the black swallowtail’s larval stage, known as the parsley worm, which feeds on their leaves.

When the caterpillar transforms into an adult butterfly, it has a lifespan of about 14 days, during which it feeds on flowers to obtain nectar.

Here is a comparison table of the black swallowtail’s interaction with selected native plant species:

Plant SpeciesHost for Parsley WormNectar Source for Adult Butterfly

Black swallowtail butterflies contribute to the pollination of native plants and help maintain the region’s biodiversity.

Thus, by understanding the cultural and historical significance of these insects, we can better appreciate their role in our ecosystems and strive to conserve their populations for generations to come.


In conclusion, the Black Swallowtail butterfly, or Papilio polyxenes, is a marvel of nature, renowned for its striking black and yellow markings and unique life cycle.

Native to North America, it thrives in open spaces, undergoing a transformative journey from egg to adult. Its diet varies across life stages, with caterpillars favoring plants like parsley and dill, while adults seek nectar-rich flowers.

Their vibrant appearance serves as both a defense mechanism and a symbol of transformation in various cultures.

Human interactions can influence their populations, emphasizing the importance of sustainable practices to ensure their continued presence in our ecosystems.


  1. 2 3

  2. 2 3

  3. 2

  4. Missouri Department of Conservation

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about black swallowtails. Scroll down to have a look at some of them.

Letter 1 – Two Black Swallowtail Caterpillars

Well way cool. 🙂 I’ve been to the site you mention, an excellent resource. I note you had a request for a better picture of swallowtail caterpillars. I’ll attach one of my better ones, taken recently. These two are feeding on volunteer fennel in our garden.

I’m not positive, but these are likely Black Swallowtail caterpillars. THanks again for the IDs. Wonderful site. Bookmarked. I’ll be back often. I’ll send a separate note with a photo of a click beetle for your collection.

I’m glad we could be helpful Jim. I don’t know if you have Anise Swallowtails, Papilio zelicaon, in your area. The caterpillars of Black Swallowtails and Anise Swallowtails look very similar. Thanks for the photo. It is pretty great.

Letter 2 – Parsleyworm: Black Swallowtail Caterpillar, early instar

Photo for the Orange, white and black caterpillar – can’t identify
Hello Bugman!
We hope you can help us out. A photo of our unknown caterpillar is attached. We found it on May 9th in the garden eating a parsely plant. We live in South East Florida (near Fort Lauderdale).

The caterpillary is fairly small, about 1/2 an inch in size. It has black and white stripes around it, with orange dots at the base of black horns or bristles on each segment. We found one photo of something similar on the Internet, but it was not identified. Can you help?
The Castro Family

Dear Castro Family,
Caterpillars shed their skins going through stages known as instars. This is an earlier instar of a Black Swallowtail Caterpillar, Papilio polyxenes. According to BugGuide, the caterpillar changes dramatically with each molt. They are sometimes called Carrotworms or Parsleyworms since they feed on the leaves of carrots as well as parsley and other plants in that family.

Letter 3 – Zebra Swallowtail and Black Swallowtail

2 different swallowtail butterflies
July 12, 2010
Hi again Bugman!,
Congrats on the book!
This afternoon near Garnett, Kansas (that’s about an hour and a half South and a little West of Kansas City) I was out looking for interesting photo ops in a field of wildflowers, and saw what I thought was a Tiger Swallowtail butterfly. About 15 seconds looking through your butterfly pages, and I’m pretty sure what I’ve got here is a Zebra Swallowtail.

It did not seem a bit put out by my presence, which surprised me because it’s wings were a little battered, you know the way they might look if a bird had gotten a taste?, even so, it was a beaut’ and it allowed me to make many attempts at a clear photo.

While I was following it around another type of Swallowtail showed up, and I managed to get a reasonable pic of that one also, though it was not nearly as accommodating as the first one.

I can’t find one that matches it on WTB anywhere! I wondered if you could help me out with that? Both butterflies are striking. They are roughly identical in size. The mystery one is mostly black with vivid yellow spots on it’s wings in the shape of a V.

Both of them have a small group of red and blue spots on the hind wings, so I gave some thought to the possibility of sexual dimorphism. Did I spell that right?, but now I’m leaning toward two different species.
The coolest thing to me though, is the several rows of yellow dots down the black one’s abdomen.
July/11/10, Temperature in the mid-80s F, though it felt more like upper 90s.
Thanks in advance!
Jeff in T-Town
Eastern Kansas, USA

Zebra Swallowtail

Hi Jeff,
Thanks for your thoughtful letter and great photos of a Zebra Swallowtail and a male Black Swallowtail.  The Black Swallowtail does exhibit sexual dimorphism.  The difference between male and female Black Swallowtail,
Papilio polyxenes, is summed up on BugGuide as: 

Female, with its large blue patches on hindwings, is a mimic of the Pipevine Swallowtail. Some female Black Swallowtails have little yellow on wings above. Males have more extensive broken yellow band.”  You can also see comparison photos on BugGuide’s Info page.

Letter 4 – Pre-Pupal Black Swallowtail Caterpillar and Butterfly Garden

Interesting moths and butterflies?
Location: Windsor, ON, Canada
August 2, 2011 12:10 pm
This doesn’t seem like a question you would normally get, but I am quite interested in Lepidoptera and I am wondering what are some easy ways to attract interesting and beautiful species?
I am currently raising a Black swallowtail caterpillar, which is about to pupate, that I found on my parsley,in my garden.
Next year, I am going to plant a strawberry plant, and I know it will attract many moths, including the Emperor moth. Anyway, are there any nice species that I can attract easily with a host plant? Preferably not a tree. A shrub, plant, flower ..etc will work.
Signature: Sincerely, Dante

Pre-Pupal Black Swallowtail Caterpillar

Hi Dante,
Thank you for submitting your lovely photo of a Pre-Pupal Black Swallowtail Caterpillar.  There is nothing unusual about your request.  It would be really helpful to know what species you are trying to attract, and also if you are wanting to provide just nectar for the butterflies, or host plants for caterpillars. 

Butterfly Bush, Buddleia species, are famous for attracting butterflies.  As a youngster growing up in Ohio, Daniel used to give his mother a bit of grief for damaging her tall perennial Phlox flowers in an attempt to catch butterflies.  The Phlox would attract numerous species of nectaring butterflies, including Tiger Swallowtails, Black Swallowtails, Spicebush Swallowtails and Pipevine Swallowtails as well as Fritillaries, Monarchs and diurnal Sphinx Moths. 

Zinnias are another excellent flower to attract nectaring butterflies, but they are annuals that need to be planted each year.  Coneflowers and Monarda are also good choices for perennials.  You can always add native milkweed to your garden to provide the host plant for Monarch Caterpillars and the blossoms attract numerous butterflies.  Good luck.

Thank you for replying, I want to provide host plants for caterpillars,  preferably simple plants, not trees.
I was thinking about planting strawberries to attract Small emperor moths , but I am not sure if they live in Detroit, MI. Are there any silk moths, sphinx/hawk moths or butterflies that I can attract easily with a host plant?
Sincerely, Dante

Hi again Dante,
We are not certain where you heard about strawberries, but we have our doubts.  Regarding Giant Silkmoths, they do not feed as adults.  Lights will attract them, but you need host trees and you are not interested in planting trees.  Hawkmoths can be attracted by flowers with nectar, like bee balm, honeysuckle and nicotiana.  Tomato plants will attract species that feed on tomato leaves.  Good Luck.

Letter 5 – Parsley Worm is Black Swallowtail Caterpillar

Subject:  Caterpillar
Geographic location of the bug:  Gettysburg, PA
Date: 07/24/2018
Time: 06:08 PM EDT
Your letter to the bugman:  What is this. Just found it on my parsley plant.
How you want your letter signed:  Tina

Parsley Worm or Black Swallowtail Caterpillar

Dear Tina,
This is a Black Swallowtail Caterpillar, and some common names are “Dill Worm, Parsley Worm, Celery Worm, Carrot Worm, Fennel Worm” according to BugGuide, because “The common names for the caterpillars vary because they can be found on many important cultivated plants in the Carrot Family. Pick the host plant, add the word ‘worm’, and you have another common name that has probably been used and published somewhere.”

Letter 6 – Parsley Worm is Black Swallowtail Caterpillar

Subject:  Electric Caterpillars Eating Parsley
Geographic location of the bug:  Mantaloking, NJ
Date: 08/04/2019
Time: 11:47 AM EDT
Your letter to the bugman:  Dear Bugman,
These neon caterpillars were enjoying a parsley buffet in a backyard near the bay in Jersey. Wondering what they will be after they transition…
How you want your letter signed:  Melanie on the Irish Chain

Black Swallowtail Caterpillar

Dear Melanie on the Irish Chain,
This is a Black Swallowtail Caterpillar, often called a Parsley Worm or Carrot Worm by home gardeners because of their host plants.  The adult Black Swallowtail is a beautiful butterfly.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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3 Comments. Leave new

  • We had lots of Black Swallowtail caterpillars last year on fennel, but none this year at all. Am i off on their timing? What months should we be seeing the caterpillars and subsequent chrysalis in Southern Georgia?

  • Julie A G Evans
    January 3, 2022 10:29 am

    I have many, many yellow jackets and wasps in my property. They seem to be attracted to the caterpillars. How can I rid my place of the caterpillars?


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