Anise Swallowtail Caterpillar vs Black Swallowtail Caterpillar: A Fascinating Comparison

Anise swallowtail caterpillar and black swallowtail caterpillar are two fascinating butterfly larvae known for their striking appearance and unique feeding habits.

Both species belong to the Papilionidae family, but they exhibit some differences in color patterns and host plants that set them apart.

This article aims to provide an insightful comparison between the two, shedding light on their key characteristics and ecological roles.

Anise Swallowtail vs Black Swallowtail Caterpillars

Distinguishing Physical Features

Anise Swallowtail caterpillars are part of the Papilio zelicaon species, featuring large larvae that appear pale green with black bands containing orange spots.

The amount of green and black on the larvae may vary based on environmental conditions, such as humidity and temperature.

File:Anise swallowtail in Caterpillar stage.jpg
Anise Swallowtail Caterpillar. Source: Bento00, Public domain, via Wikimedia Commons

Black Swallowtail caterpillars belong to the Papilio polyxenes species and have a more distinctive appearance compared to Anise Swallowtail caterpillars.

The adult Black Swallowtail butterfly exhibits black upper wings with two rows of yellow spots.

You will also notice blue, and orange-red coloring on the wings, with females showcasing smaller spots and a more iridescent-blue tone.

Black Swallowtail Caterpillar. Source: Beatriz Moisset, From Wikimedia Commons

Here are the main differences in physical features:

  • Anise Swallowtail: Pale green with black bands containing orange spots 1
  • Black Swallowtail: Black wings with yellow, blue, and orange-red coloring, and iridescent-blue for females

Comparison of Size

Regarding size, female Black Swallowtail butterflies tend to be larger than males, with a wingspan of 3¼ to 4¼ inches. The Anise Swallowtail has a wingspan of 2.4 to 4 inches.

A comparative table showing the size differences:

Anise Swallowtail2.4 to 4 inches
Black Swallowtail3¼ – 4¼ inches (♀)

Habitat and Distribution

Anise Swallowtail Caterpillar

The Anise Swallowtail caterpillar can be found throughout Western North America, including the California coast and Utah. Their habitats may vary, but they are generally found in:

  • Open fields
  • Bare hills
  • Gardens

These caterpillars usually feed on host plants such as anise, dill, fennel, and parsley.

Black Swallowtail Caterpillar

The Black Swallowtail caterpillar has a wide distribution across southern Canada, the eastern and mid-western United States to the Rocky Mountains, and southwest into Arizona and northern Mexico. Their preferred habitats include:

  • Open areas
  • Fields
  • Meadows
  • Parks
  • Wetlands
  • Prairies

Black Swallowtail caterpillars typically feed on plants such as parsley, dill, and carrot leaves.

Comparison Table

FeatureAnise Swallowtail CaterpillarBlack Swallowtail Caterpillar
RangeWestern North AmericaEastern & Mid-Western US, Northern Mexico
HabitatOpen fields, bare hills, gardensOpen areas, fields, meadows, parks, wetlands, prairies
Typical Host PlantsAnise, dill, fennel, parsleyParsley, dill, and carrot leaves
Anise Swallowtail Caterpillar

Host Plants and Feeding Behavior

Anise Swallowtail Caterpillar

The Anise Swallowtail caterpillar belongs to the Papilionidae family. It feeds primarily on plants from the carrot and citrus families (Apiaceae and Rutaceae). Examples of preferred host plants:

  • Fennel (Foeniculum vulgare)
  • Lomatium dissectum
  • Parsley

These larvae change their appearance as they grow. Small larvae resemble bird droppings, while larger ones have pale green and black bands with orange spots.

Black Swallowtail Caterpillar

The Black Swallowtail caterpillar also belongs to the Papilionidae family. It feeds mainly on plants within the Apiaceae family, such as:

  • Parsley
  • Dill
  • Carrot

These caterpillars go through similar appearance changes, starting as bird-dropping mimics before displaying green and black bands with yellow spots as they grow.

Comparison Table:

FeatureAnise Swallowtail CaterpillarBlack Swallowtail Caterpillar
Primary Host Plant FamiliesApiaceae, RutaceaeApiaceae
Examples of Host PlantsFennel, Lomatium dissectum, ParsleyParsley, Dill, Carrot
Larval AppearanceBird droppings, green/black bands with orange spotsBird droppings, green/black bands with yellow spots

In conclusion, both Anise and Black Swallowtail caterpillars feed on plants from the Apiaceae family, but Anise Swallowtails also feed on Rutaceae plants. They exhibit similar larval appearance changes but differ in color patterns.

Anise Swallowtails

Life Cycle and Development

Anise Swallowtail Caterpillar

The Anise Swallowtail Caterpillar (Papilio zelicaon) has a fascinating life cycle. The eggs are laid on host plants, such as sweet cicely or anise root, and the larvae resemble bird droppings when they are small.

As they grow into larger caterpillars, their appearance changes to a pale green color with black bands containing orange spots. Environmental factors, such as heat and humidity, can affect the coloration of these caterpillars.

File:Anise Swallowtail Life Cycle.svg
Source: Bugboy52.40CC BY-SA 3.0, via Wikimedia Commons

The pupa stage, in which the caterpillar forms a chrysalis and transforms into the anise swallowtail butterfly, may result in brown or green pupae.


  • Well-camouflaged due to its resemblance to bird droppings
  • Coloration changes according to environmental conditions


  • Color changes may make it difficult to identify

Black Swallowtail Caterpillar

The Black Swallowtail Caterpillar (Papilio polyxenes) also has an interesting life cycle, beginning with eggs laid on plants in the carrot family (Apiaceae).

These caterpillars are various shades of green, featuring narrow black bands on each body segment and interrupted by yellow-orange dots. As they grow, they reach lengths of up to 2 inches.

They have a defense mechanism called osmeteria, which are retractable, forked structures that release a foul odor when threatened. In the pupal stage, they spin a silk pad to attach themselves to a surface before forming a chrysalis.

Black Swallowtail Caterpillar 1st Instar. Source: WanderingMogwai, From Wikimedia Commons

Anise Swallowtail CaterpillarBlack Swallowtail Caterpillar
Larval appearancePale green with black bands, orange spotsGreen with black bands, yellow-orange dots
Pupa colorBrown or greenN/A
Host plantsSweet cicely, anise rootCarrot family (Apiaceae)
OsmeteriaNot presentPresent
WingspanNot applicable (caterpillar stage)Not applicable (caterpillar stage)

Identifying Adult Butterflies

Anise Swallowtail Butterfly

The Anise Swallowtail butterfly is a member of the Papilionidae family. Males and females exhibit some degree of sexual dimorphism.

  • Wingspan: Typically ranges from 2.4 to 4 inches
  • Appearance: Yellow with black markings, blue and orange spots near the tail.
  • Habitat: Found mainly in the western United States, preferring open meadows and hillsides.
Anise Swallowtail Butterfly

Black Swallowtail Butterfly

The Black Swallowtail butterfly belongs to the same family as the Anise Swallowtail.

  • Wingspan: Approximately 2.7 to 4.1 inches (7 to 10.5 cm).
  • Appearance: Black with yellow markings on the edge, blue and red spots on the hindwings.
  • Habitat: Primarily in the eastern United States, inhabiting gardens, fields, and meadows.
Black Swallowtail Butterfly. Source: D. Gordon E. Robertson, From Wikimedia Commons.

Here’s a comparison table highlighting the differences between the Anise Swallowtail and the Black Swallowtail butterflies:

FeatureAnise SwallowtailBlack Swallowtail
Wingspan2.4 to 4 inches (6 to 10 cm)2.7 to 4.1 inches (7 to 10.5 cm)
ColorYellow with black markingsBlack with yellow markings
SpotsBlue and orange near tailBlue and red on hindwings
HabitatWestern USEastern US

Both butterflies can be confused with Tiger Swallowtail, Pipevine Swallowtail, and Spicebush Swallowtail due to their similar appearances. However, observing their distinct markings and color patterns can help differentiate them.

Raising and Caring for Caterpillars

Anise Swallowtail Caterpillar

Anise swallowtail caterpillars are typically found on plants in the carrot family, like anise and fennel. Female anise swallowtails lay their eggs on these host plants, providing a food source for the developing caterpillars.

To raise anise swallowtail caterpillars:

  • Obtain a third instar caterpillar or a live female to lay eggs
  • Provide potted parsley or fennel plant for food and shelter
  • Create a safe environment using a cage or enclosure
  • Mist the cage daily for humidity and ventilation

Remember to be gentle when handling caterpillars to avoid injury.

Black Swallowtail Caterpillar

Black swallowtail caterpillars also enjoy plants from the carrot family, such as parsley, dill, and fennel. They can be found munching on herbs in gardens and open areas.

To raise black swallowtail caterpillars:

  • Obtain a third instar caterpillar or a live female to lay eggs
  • Provide potted parsley or dill plant as their food source
  • Set up a suitable enclosure or cage to keep them safe
  • Ensure a humid environment by misting the cage daily

Handle them with care to prevent injuries.

Comparison Table

AspectAnise Swallowtail CaterpillarBlack Swallowtail Caterpillar
Host PlantsAnise, FennelParsley, Dill, Fennel
Cage EnvironmentMist daily for humidity and ventilationMist daily for humidity
Obtaining CaterpillarsThird instar caterpillar or live femaleThird instar caterpillar or live female

Conservation Status and Human Impact

Anise Swallowtail

The Anise Swallowtail (scientific classification: Papilio zelicaon) is native to western North America, where it coexists with other species like the Western Tiger Swallowtail (Papilio rutulus).

This butterfly thrives in various habitats including roadside, gardens, and open fields. However, the conservation status of Anise Swallowtail is not directly provided by NatureServe or other major conservation organizations.

Anise Swallowtail Butterfly

Black Swallowtail

On the other hand, the Black Swallowtail (scientific classification: Papilio polyxenes) is native to eastern North America and shares some habitats with the Eastern Tiger Swallowtail (Papilio glaucus).

Its subspecies, the Indra Swallowtail (Papilio indra), is found in the western regions. The Black Swallowtail is often seen in gardens and wooded areas.

Similar to the Anise Swallowtail, its conservation status is not explicitly mentioned by NatureServe or other major conservation organizations.


Both Anise and Black Swallowtails are similar in size and frequently mistaken for each other due to their overlapping habitats. They coexist with different subspecies of tiger swallowtail butterflies.

As of now, neither species is facing significant threats or concerning conservation status, and they continue to thrive in their natural habitats, gardens, and roadsides.


  1. Anise Swallowtail Information 2 3 4 5

  2. Black Swallowtail Information 2 3 4 5 6 7 8

  3. 2 3 4 5

Readers’ Mail

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

Letter 1 – Anise Swallowtail Caterpillar

could you tell me what this is?
hi I live in california Southern….and found this guy..but would live to know what it will turn into.

This is an Anise Swallowtail Caterpillar. They resemble Black Swallowtail Caterpillars, but as you live in Southern California and that is the range of the Anise Swallowtail, we are sure it is the Papilio zelicaon.

The orange horns are an intricate defense mechanism. If the caterpillar is disturbed, it rears up and reveals these orange fleshy organs that release a foul odor.

Letter 2 – Anise Swallowtail Caterpillar

What is our bug?
We found this guy munching on our parsley, Just wondering what he is?? Thanks,
Ashleigh and Christian
Hermosa Beach, Ca

Hi Ashleigh and Christian,
This Anise Swallowtail Caterpillar will metamorphose into a beautiful large black butterfly with tails and yellow spots.

Letter 3 – Anise Swallowtail Caterpillar

3 pictures for you
Hi Mr. Bugman,
I am attaching three photos I took this morning of the caterpillar you identified for me on your website. You asked for clearer pictures; I hope these help. You do a great service, and I love your site. Regards,
Darlene Elliott
Santa Rosa, California

Hi Darlene,
Thank you for sending us your images of an Anise Swallowtail Caterpillar, Papilio zelicaon. IN the final instar, we find the caterpillar of the Anise Swallowtail to be visually indistinguishable from images of the Black Swallowtail Caterpillar, Papilio polyxenes.

If a reader does not supply a location, we would not be able to tell them apart. The Anise Swallowtail is found in the Western U.S. while the Black Swallowtail is limited to the east.

The Black Swallowtail Caterpillar is sometimes called a Parsleyworm, and as your photo indicates, the name also applies to the Anise Swallowtail.

Letter 4 – Anise Swallowtail

Anise Swallowtail
Hi Lisa Anne and Daniel:
I recall you mentioned seeing Anise S’tails this Spring but I have seen no recent submissions. A shame, they are high on my list of favorites in central WY. Peace,

Hi Dwaine,
Thank you for your beautiful contribution. We are seeing many Anise Swallowtails and Tiger Swallowtails in our Mt Washington, Los Angeles garden, and this past weekend we saw the first Giant Swallowtail of the season.

We received a lovely image of an Anise Swallowtail Caterpillar today as well, but time constraints may prevent us from posting it.

Letter 5 – Anise Swallowtail Caterpillar

Bander caterpillar, Golden Gate Park, San Francisco
August 1, 2009
Hi. I found this gorgeous caterpillar hanging on to a stalk of poison hemlock yesterday in Golden Gate Park, San Francisco yesterday. (It’s August first today.) I’m dying to know what kind of butterfly or moth it will become.
Golden Gate Park, San Francisco, CA

Anise Swallowtail Caterpillar
Anise Swallowtail Caterpillar

Hi Harvey,
This is an Anise Swallowtail Caterpillar, Papilio zelicaon.  The caterpillars are generally found on sweet fennel (Foeniculum vulgare) which is an introduced plant.  It is also found on carrot tops and parsley in the home garden. 

According to Charles Hogue in his book, Insects of the Los Angeles Basin, “Before the introduction of these foreign plants, the larvae fed on various native umbellifers, such a Lamotium, Heracleum, and Tauschia species.” 

We have never heard of them feeding on Poison Hemlock, Conium maculatum, but as it is in the same family, Apiaceae, as the other plants, this is not unusual.

Letter 6 – Anise Swallowtail Caterpillar

June 7, 2010
Found this little guy today feeding on a plant that seems like a wilder variety of cilantro. Reminded me of a monarch larva. Is it a nymphalid?
L.Rakestraw, Tucson, AZ
Tucson (near Canada del Oro Wash)

Anise Swallowtail Caterpillar

Dear L.
We are quite jealous.  Despite that we have a field of carrots in bloom in our front yard and that we see Anise Swallowtails in our garden, we have yet to discover Anise Swallowtail Caterpillars feeding on our carrot plants. 

We have found Anise Swallowtail Caterpillars feeding on wild fennel in the open space nearby.

Thank you!  This one would be a great candidate to raise for the kids.  I can dig up some of that plant and pot it and put it in a screen cage.

Side note: I also sent the picture asking if it was a Pyrgotid fly, but I am almost certain now that it is a picture-wing fly, Otitidae or Ulidiidae, due to the shape of the abdomen and the fact that those *do* occur here. 

Also, there are no May beetles here and we have plenty of compost in our yard, which Otitids consume!

Hi Lisa,
The Anise Swallowtail is great for kids because the butterfly is so pretty.  When a drab brown moth emerges, the impact is not as great.  We will try to post your picture winged fly if we have a chance.

Letter 7 – Anise Swallowtail and unidentified Blue from Oregon

Subject: Tiger Swallowtail?
Location: Southern Oregon
July 14, 2012 2:04 pm
Found these on the side of Mt. Ashland, Siskiyou Mtns. yesterday at about 5000’ elev. One’s a bit different than other tiger swallowtails in color and maybe a bit smaller.
The other is blue, but what sort?
Signature: TerryDarc

Anise Swallowtail

Hi TerryDarc,
We were uncertain at first if this was an Anise Swallowtail,
Papilio zelicaon, or an Old World Swallowtail, Papilio machaon, because they look so similar.  To further complicate matters, both species have dark and yellow forms. 

We learned in Jeffrey Glassberg’s book Butterflies Through Binoculars, the West, that the Anise Swallowtail can be distinguished from other similar-looking swallowtails because the “black spot at HW outer angle is small and centered” within the orange spot. 

This was verified on BugGuide which states:  “Upper surface of hindwing has yellow-orange eyespot near tail with round black center that is not connected to hindwing margin.” 

We are uncertain of the identity of the Blue, but perhaps one of our readers will be able to supply an answer.  We suspect it is either an Azure (see BugGuide) or one of the Arctic Blues (see BugGuide).  Your photos are both quite lovely and detailed.

What’s That Blue???

Thanks, Daniel.
If by Old World Swallowtail is meant Europe or such, then this was an Anise Swallowtail b/c the picture was taken in southern Oregon. I am clueless about the blues but I know there are a bunch of them.

Thanks for the kind words about the photos. My wife says they’re already posted to Thanks so much for doing these two. Great site!

Hi, again Terry,
The Old World Swallowtail is established in western North America, but it is originally from Eurasia.

Thanks! I guess I never thought about someone importing butterflies. BTW – I made a donation to WTB. You guys deserve it!

Hi, again Terry,
We are not certain how the Old World Swallowtail was introduced to the New World.  We suspect it was an accidental introduction of plants that were brought from Europe to grow on American soil. 

That was very kind of you to make a donation.  See these BugGuide categories for the subspecies of the Old World Swallowtail and the Anise Swallowtail.
Papilio machaon bairdii – Baird’s Swallowtail
Subspecies Papilio machaon oregonius – Oregon Swallowtail
Subspecies Papilio zelicaon nitra – Anise Swallowtail
Papilio zelicaon zelicaon – Anise Swallowtail


  • 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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6 thoughts on “Anise Swallowtail Caterpillar vs Black Swallowtail Caterpillar: A Fascinating Comparison”

    • Thanks for the input. We find the Blues a very difficult group to identify conclusively. There are so many similar looking species and subspecies and local variations.

  1. I just found this very caterpillar munching on my flat leaf parsley. I live just west of tulsa, ok. Is this little guy going to be alright? I’very never seen one in my garden. It is identical to the picture the person posted from Southern California.

    Cyd GG

  2. I just found this very caterpillar munching on my flat leaf parsley. I live just west of tulsa, ok. Is this little guy going to be alright? I’very never seen one in my garden. It is identical to the picture the person posted from Southern California.

    Cyd GG

  3. I have anise swallowtail caterpillars. Sometimes I also get the caterpillar that looks like bird poop! Anyway, my question is; are lizards, praying mantis and birds enemies of these caterpillars? Anything else eat them? Thank you


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