What Do Anise Swallowtail Caterpillars Eat? Unveiling The Mystery

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The Anise Swallowtail caterpillar is a fascinating creature with specific dietary habits that play a crucial role in its growth and development. 

Native to Western North America, this caterpillar’s choice of food not only ensures its survival but also prepares it for its eventual transformation into the Anise Swallowtail butterfly. 

This article delves deep into understanding what the Anise Swallowtail caterpillar eats, why it chooses certain plants, and how its diet impacts its life cycle. 

Let’s explore the dietary world of this intriguing caterpillar.

What Do Anise Swallowtail Caterpillars Eat
Prepupal Anise Swallowtail Caterpillar

Physical Characteristics & Identification


The Anise Swallowtail caterpillar, scientifically known as Papilio zelicaon, is a captivating creature that undergoes significant transformations in its appearance as it progresses through its developmental stages.

In its early instars, the caterpillar is predominantly dark brown, almost black, which might be a strategy to resemble bird droppings, a common form of camouflage among caterpillars. 

This dark hue is punctuated by an irregular white band around its middle, giving it a distinctive look. As it grows and moves through successive molts, the caterpillar begins to exhibit a shift in its color palette. 

The dark brown starts to give way to shades of green. By the time it reaches its fifth and final instar, the caterpillar boasts a predominantly green body. 

This vibrant green is adorned with markings in black, orange, and light blue, making it a visual treat and easily distinguishable from many other caterpillar species.

Another fascinating aspect of its physical characteristics is the presence of bright orange osmeteria, or “stinkhorns”, which are eversible glandular structures located just behind its head. 

When threatened, the caterpillar can protrude these structures as a defense mechanism, releasing a foul odor to deter potential predators.

Anise Swallowtail Caterpillars

Anise Swallowtail Butterfly

The Anise Swallowtail butterfly, the mature form of the Papilio zelicaon caterpillar, is a strikingly beautiful creature that captures the essence of nature’s artistry.

Upon emerging from its chrysalis, the Anise Swallowtail reveals its large, vibrant wings that span anywhere from 2 ¾ to 3 ½ inches

The primary color of the wings is yellow, interspersed with black bands and spots. 

The forewings showcase a series of black bands, while the hindwings are adorned with a blue crescent and an orange-red eyespot near the tail. 

This combination of colors not only makes the butterfly visually appealing but also aids in confusing or deterring potential predators.

One of the most distinguishing features of the Anise Swallowtail, as with other swallowtails, is the presence of the “tail” on the hindwings. 

These tails, along with the red eyespots, mimic the appearance of antennae, potentially confusing predators about the butterfly’s head orientation and giving the butterfly a chance to escape when under threat.

Anise Swallowtail

The underside of the butterfly’s wings is equally mesmerizing. It is paler in color, with the yellow regions appearing more cream-like, and the black, blue, and red patterns appearing more subdued. 

This coloration provides excellent camouflage when the butterfly is resting on flowers or foliage.

In flight, the Anise Swallowtail is graceful and agile. Its wing patterns create a mesmerizing visual as it flits from flower to flower, making it a favorite among butterfly enthusiasts and photographers alike.

Life Cycle, Metamorphosis, and Lifespan of the Anise Swallowtail

Life Cycle and Metamorphosis

  • Egg: The life of an Anise Swallowtail begins as a tiny, spherical egg, usually laid on the leaves of host plants, particularly those in the carrot family. Depending on the temperature and conditions, the egg will hatch in a few days to a couple of weeks.
  • Caterpillar (Larva): Once hatched, the caterpillar emerges, and its primary goal is to eat and grow. As it consumes the leaves of its host plant, it undergoes several molting stages, shedding its skin to accommodate its growing body. This larval stage lasts for several weeks.
  • Pupa (Chrysalis): After reaching its full size, the caterpillar finds a secure spot, often on twigs or stems, to form its chrysalis. Within this protective casing, the caterpillar undergoes a remarkable transformation, rearranging its cells and body structure. This pupal stage can last from a couple of weeks to several months, depending on environmental conditions.
  • Butterfly (Adult): From the chrysalis emerges the adult Anise Swallowtail butterfly. With its vibrant wings, it is now ready to fly, mate, and lay eggs, thus completing the life cycle.
Anise Swallowtail Caterpillar

How Long Do Anise Swallowtail Butterfly Live?

The adult Anise Swallowtail butterfly, once emerged from its chrysalis, typically has a lifespan ranging from six to fourteen days

What Do Anise Swallowtail Caterpillars Eat?

The Anise Swallowtail caterpillar, like many caterpillars, is selective about its food sources, displaying a strong preference for specific plants that provide the necessary nutrients for its growth and development. 

Central to its dietary choices is the carrot family, or Apiaceae, a group of aromatic plants that are not only essential for the caterpillar’s sustenance but also play a role in its survival strategy.

Sweet fennel and wild fennel stand out as the primary host plants for the Anise Swallowtail caterpillar. 

These plants not only offer the caterpillar a rich source of nutrition but also provide a habitat where the caterpillar can thrive, grow, and eventually metamorphose into its butterfly form. 

Anise Swallowtail Caterpillars

The aromatic nature of fennel might also play a role in deterring certain predators, offering the caterpillar an added layer of protection.

While sweet and wild fennel are the caterpillar’s primary choices, its palate is not limited to these plants alone. 

The caterpillar is also known to feed on other members of the carrot family. 

Parsley, with its lush green leaves, offers another nutritious food source. 

Dill, another aromatic herb from the Apiaceae family, is also occasionally part of the caterpillar’s diet. 

These plants, with their distinct flavors and aromas, not only nourish the caterpillar but might also influence the taste or smell of the caterpillar, potentially making it less appealing to certain predators.

To summarize:

  • Primary Host Plants: Sweet fennel and wild fennel are the caterpillar’s primary food sources, providing essential nutrients and a suitable habitat.
  • Additional Food Sources: Beyond fennel, the caterpillar also consumes other plants from the Apiaceae family, including Parsley and Dill 

What Does Anise Swallowtail Butterflies Eat?

The Anise Swallowtail butterfly, upon reaching its mature form, undergoes a significant shift in its dietary preferences. 

Unlike its caterpillar stage, which feeds primarily on specific plants from the carrot family, the butterfly is drawn to the sweet nectar of flowers.

Nectar serves as the primary source of energy for the Anise Swallowtail butterfly, providing it with the essential sugars and nutrients required for its daily activities, including flight, reproduction, and defense. 

The butterfly’s proboscis, a long, tube-like tongue, is perfectly adapted for sipping nectar from the depths of flowers.

As for the flowers they are attracted to, the Anise Swallowtail butterfly has a range of preferences. Some of the common flowers that these butterflies frequent include:

  • Lilac: Known for its fragrant clusters of flowers.
  • Coneflowers: Recognizable by their large, daisy-like appearance.
  • Milkweed: A favorite among many butterfly species, not just the Anise Swallowtail.
  • Goldenrod: Tall plants with bright yellow flowers.
  • Zinnias: Colorful flowers that come in a variety of hues.
  • Marigolds: Bright orange or yellow flowers that are common in gardens.
  • Phlox: Clusters of pink, purple, or white flowers.
Anise Swallowtail

Habitat and Distribution of the Anise Swallowtail Caterpillar

Geographical Distribution

The Anise Swallowtail caterpillar is predominantly found in regions of Western North America. 

This includes areas stretching from Alaska down to Baja California and even as far east as the western Great Plains

These regions offer the ideal climate, vegetation, and protection for the caterpillar to grow and metamorphose into its butterfly form.


Proximity to Food Plants: Given its dietary preference for plants from the carrot family, especially sweet and wild fennel, these caterpillars are often found in areas where these plants are abundant. 

This ensures that the caterpillar has a consistent and readily available food supply, crucial for its rapid growth and development.

Gardens: Due to the popularity of plants like parsley, dill, and fennel in home gardens, it’s not uncommon to find Anise Swallowtail caterpillars in residential areas. 

Gardeners might spot them munching on their herb plants, and while they might be seen as pests, they are a testament to a healthy, pesticide-free garden.

Hilltops: An interesting behavior of the mature Anise Swallowtail butterfly, which indirectly affects the caterpillar’s habitat, is hilltopping. 

Adult butterflies often fly to hilltops for mating rituals. As a result, caterpillars can sometimes be found in regions surrounding these hilltops, indicating the butterfly’s preference for laying eggs in these areas.

Anise Swallowtail Ovipositing

Unique Behavioral Traits and Defense Mechanisms

The Anise Swallowtail caterpillar, while delicate in appearance, is equipped with a set of intriguing behavioral traits and defense mechanisms that ensure its survival in the wild. 

These adaptations not only protect the caterpillar from potential threats but also offer a glimpse into the intricate ways nature equips its creatures for survival.

Osmeteria (Horns) and Their Role

One of the most distinctive defense mechanisms of the Anise Swallowtail caterpillar is the presence of osmeteria, often referred to as “stinkhorns.” 

These are forked, bright orange glandular structures located just behind the caterpillar’s head. 

Typically hidden, the osmeteria are everted or pushed out when the caterpillar feels threatened. 

When exposed, they release a foul-smelling chemical, which serves multiple purposes. 

Firstly, the odor can deter potential predators, making them think twice before making a meal of the caterpillar. 

Secondly, the bright orange color of the osmeteria can be startling, adding another layer of defense by visually warning off threats.

Anise Swallowtail with Osmeterium

Are Anise Swallowtail Caterpillars Poisonous?

A common question that arises, given the caterpillar’s defense mechanisms, is whether they are poisonous. 

While the osmeteria emit a foul odor, the caterpillar itself is not considered toxic or harmful when touched. 

However, the chemicals released from the osmeteria might cause mild irritation to some individuals, especially if they come into contact with sensitive areas like the eyes. 

It’s always advisable to handle any wildlife, including caterpillars, with care and to wash hands after touching them.

Potential Threat to Predators

For predators, the combination of the caterpillar’s odor and potential taste deterrence (from feeding on aromatic plants like fennel) makes the Anise Swallowtail caterpillar a less-than-appealing meal choice. 

While not toxic in the traditional sense, the caterpillar’s defense mechanisms effectively reduce its chances of being preyed upon.

What To Feed Swallowtail Caterpillars?

Swallowtail caterpillars, belonging to the family Papilionidae, are a diverse group with various species having specific dietary preferences. 

While the Anise Swallowtail caterpillar has its favorites, other swallowtail caterpillars also have their unique host plants. 

General Dietary Preferences

Swallowtail caterpillars are herbivores, feeding primarily on the leaves of specific host plants. These plants provide the caterpillars with essential nutrients, allowing them to grow and eventually metamorphose into butterflies.

Prepupal Tiger Swallowtail Caterpillar

Specific Preferences

  • Eastern Black Swallowtail (Papilio polyxenes): This caterpillar prefers plants in the carrot family (Apiaceae). Common host plants include parsley, dill, fennel, and Queen Anne’s lace.
  • Giant Swallowtail (Papilio cresphontes): These caterpillars often feed on citrus trees. This includes oranges, lemons, limes, and grapefruits.
  • Spicebush Swallowtail (Papilio troilus): Their primary diet consists of spicebush (Lindera benzoin) and sassafras trees (Sassafras albidum).
  • Eastern Tiger Swallowtail (Papilio glaucus): They have a varied diet, feeding on trees like tulip trees (Liriodendron tulipifera), black cherry (Prunus serotina), and plants like sweetbay magnolia (Magnolia virginiana).
  • Zebra Swallowtail (Eurytides marcellus): These caterpillars feed on plants in the pawpaw family (Annonaceae), specifically the pawpaw tree (Asimina triloba).
  • Pipevine Swallowtail (Battus philenor): Their diet revolves around plants known as pipevines or Dutchman’s pipevines (Aristolochia species).
  • Anise Swallowtail (Papilio zelicaon): As previously discussed, their primary diet includes sweet fennel, wild fennel, and other plants in the carrot family.

Considerations When Feeding

If you’re raising swallowtail caterpillars, it’s essential to provide fresh leaves from their specific host plants. 

Ensure that the plants are free from pesticides, as these can harm or kill the caterpillars. 

Regularly replenish the food source, especially as the caterpillars grow and their appetites increase.

Caring for a Swallowtail Caterpillar

Raising a swallowtail caterpillar can be a rewarding experience. However, to ensure the health and successful development of the caterpillar, certain guidelines and care practices should be followed.

  • Enclosure: Use a well-ventilated container or netted cage as an enclosure. This provides protection from predators while ensuring adequate airflow.
  • Temperature and Humidity: Swallowtail caterpillars thrive in mild temperatures and moderate humidity. While they can tolerate a range of conditions, extreme cold or heat can be detrimental. If raising them indoors, keep them away from direct sunlight or cold drafts.
  • Sticks and Twigs: Place some sticks or twigs inside the enclosure. These will serve as structures for the caterpillar to crawl on and eventually form its chrysalis.
  • Cleanliness: Regularly clean the enclosure to remove waste (frass) and any old or uneaten food. This helps prevent mold growth and maintains a healthy environment.
  • Hydration: While caterpillars get most of their water from the food they eat, it’s a good practice to occasionally mist the enclosure with water, ensuring they have adequate hydration.
  • Observation: Keep a close eye on the caterpillar’s behavior. If it stops eating or seems lethargic, it might be preparing to pupate. Alternatively, it could be a sign of stress or illness.
  • Preparation for Pupation: As the caterpillar nears the end of its larval stage, it will start looking for a suitable spot to form its chrysalis. Ensure there are ample places within the enclosure where it can securely attach itself.


In summary, the Anise Swallowtail caterpillar primarily feeds on plants from the carrot family, especially favoring sweet fennel and wild fennel. 

As it grows, it might also consume other plants from the same family, such as parsley and dill. 

These specific dietary choices provide the caterpillar with essential nutrients for its development. 

The caterpillar’s preference for these plants not only ensures its nourishment but also plays a role in its survival, as the aromatic nature of these plants may deter certain predators. 

This dietary focus is crucial for its successful metamorphosis into the Anise Swallowtail butterfly.

Reader Emails

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

Letter 1 – Anise Swallowtail Caterpillars


Here’s a picture
I took these pictures in my back yard in Pacifica, CA. (since you ask for a better one than on your site) Thanks for telling us that they were the black swallowtail. They were on a Fennel plant but did not cocoon there… Blessings,
Tori Prince

Hi Tori,
Black Swallowtail Caterpillars and Anise Swallowtail Caterpillars look very similar. Black Swallowtails are found in the Eastern U.S. and Anise Swallowtails in the West. Your caterpillars are Anise Swallowtails.

Letter 2 – Anise Swallowtail Caterpillar or Old World Swallowtail Caterpillar


beautiful Swallowtail hi, we went huckle berry picking up here at the start of the rockies and my daughter found this beautiful caterpillar. It seemed strange to find it this far north and on a mountain, to boot! The Anise Swallowatail ranges from Canada through Washington, Oregon and California, and probably flagrantly ignores the Mexican border. Additionally, according to BugGuide, photos have been received from Utah and “A rare stray to central Nebraska and eastern North Dakota.” Just where exactly do the Rockies start? hi again, sorry, we are in Dawson Creek, Canada – in the northeast of BC, we were in the “Pine Pass” – the northern part of the highway between Dawson Creek and Prince George. It was early August. Amber I believe this could also be a caterpillar of Pike’s Old World Swallowtail, Papilio machaon pikei http://www.entomology.ualberta.ca/searching_species_details.php?fid=500761&vw=1&sb=1&r=41&o=1&c=1&s=2047&sn=Papilio+machaon+pikei Again, much obliged and continued best wishes! Keith

Letter 3 – Anise Swallowtail Caterpillars


they are probably swallowtail caterpillars Subject: Monarch caterpillars on Dill plants May 9, 2014 12:34 pm I have just seen approximately 10 of what I believe to be monarch caterpillars on my Dill plants. This surprises me as I have not planted milkweed as of yet and have not noticed any growing nearby. I was wondering if there are other caterpillars that resemble monarchs or if it is common for monarchs to feed on other plants than milkweed. Signature: Kristy they are probably swallowtail caterpillars Daniel, Thank you so much for getting back to me. I looked at some pictures of swallowtail caterpillars and I don’t think that is what they are. I have attached a photo of the caterpillars in question. If you can let me know what you think? Thanks, Kristy Subject: Re: Comment/Question: Monarch caterpillars on Dill plants
Swallowtail Caterpillars
Anise Swallowtail Caterpillars
Hi Kristy, These are definitely Swallowtail Caterpillars.  You did not provide a location.  Our first guess is that you live in the in the eastern half of the country and that these are Black Swallowtail Caterpillars, but the very similar looking Anise Swallowtail Caterpillars can be found in western states.  Both will feed on dill, carrots and parsley, as well as other related plants.  The markings and coloration of both species change as they grow and molt, and very young caterpillars of both species look more like bird droppings.  Please provide a location for your sighting. Hi Daniel, Thanks again. I live in Nevada City, California in the foothills of the Sierra Nevada. I looked at the photos of the Anise Swallowtail. I also looked at the plant again and there are also early instars. I so appreciate your help and website. I love to identify the insects present in my garden and was unaware of the Anise Swallowtail. Now I know. Thank you, Kristy Thanks for the location confirmation.

Letter 4 – Anise Swallowtail Chrysalis


Subject: What will emerge? Location: Santa Cruz, CA [Latitude: 36° 58′ 16.998″ N, Longitude: 122° 2′ 36″ W] June 11, 2015 5:07 pm My daughter noticed the cocoon shown in the attached pictures. What will emerge? Signature: Daniel & Sophia
Anise Swallowtail Chrysalis
Anise Swallowtail Chrysalis
Dear Daniel and Sophia, We believe your chrysalis belongs to an Anise Swallowtail based on its similarity to this image posted to BugGuide.

Letter 5 – Anise Swallowtail Caterpillar on Carrots


Subject:  Anise Swallowtail Caterpillar in WTB? garden Location:  Mount Washington, Los Angeles, California December 7, 2015 11:30 AM Today while digging in the dirt in preparation for planting onions, we noticed this Anise Swallowtail Caterpillar munching on carrot greens.  Though we have grown carrots for ten years, and though Anise Swallowtails are relatively common in the area, this is our first sighting of a Caterpillar in the vegetable garden.
Anise Swallowtail Caterpillar
Anise Swallowtail Caterpillar

Letter 6 – Anise Swallowtail Caterpillars on Parsley


Subject: Pleasant Surprise! Location: West Losangeles May 26, 2017 11:41 am Hi Bugman, I’ve been planting fennel for years to attract anise swallowtail butterflies with sporadic success. Can’t tell you how surprised I was to see a parsley plant covered with caterpillars. I counted 14, but there are probably more. Did a bit of research and learned the plants the larvae eat are in the carrot family, so, I guess parsley is in the carrot family? One thing I didn’t like about fennel is the caterpillars are exposed and easily seen by predators. With parsley, at least when they are small, the caterpillars are hidden by leaves. Thx, Jeff Signature: Jeff Bremer
Anise Swallowtail Caterpillars
Congratulations Jeff, We are concerned that 14 caterpillars will soon defoliate your parsley plant and that without any food, the Anise Swallowtail Caterpillars will starve before reaching maturity.  You might want to consider buying a few more parsley plants to help ensure survival.  We occasionally find Anise Swallowtail Caterpillars munching on carrots and parsley in our own garden.
Anise Swallowtail Caterpillars
Hi Daniel, More parley is on my list. I have another question for you: Over the past 10 years or so, I’ve taken hundreds of pictures of the butterflies we’ve lured into our back yard (including caterpillars, chrysalises and eggs). Would you be interested in them or know of any organizations that could use them? Thx, Jeff Hi Jeff, Hundreds arriving at one time would be overwhelming for our tiny staff, but trickling them in slowly to our site would be wonderful.  Please continue to use our standard form for submissions and please confine your submissions to a single species.  Eggs, caterpillars, chrysalides and imagos or adults of the same species arriving together though would be most welcome.  We are especially curious when you first documented the Giant Swallowtail and its caterpillar the Orange Dog as this species was first reported in Los Angeles in the late 1990s, we believe.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com 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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Tags: Anise Swallowtail Butterflies

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