Captivating California Tortoiseshell Butterflies: A Must-Know for Butterfly Enthusiasts

The California Tortoiseshell is a fascinating butterfly species native to the western United States.

With its bright orange-brown wings, dark markings, and two-inch wingspan, this eye-catching insect is hard to miss when it takes flight.

However, when perched, the Tortoiseshell can be more difficult to spot due to its mottled brown wing undersides that act as a camouflage against predators.

California Tortoiseshell

California Tortoiseshell

This butterfly is quite particular in its choice of host plant and habitat.

Adult California Tortoiseshells lay their eggs only on various species of wild lilac (Ceanothus).

This exclusive relationship between the butterfly and wild lilac plants has an essential impact on their life cycle and overall survival.

California Tortoiseshell Overview

Appearance and Wingspan

The California Tortoiseshell, a butterfly species, has a vibrant appearance with orange-brown wings adorned by dark markings.

Its wingspan measures around 1.25 to 2.75 inches.

  • Bright orange-brown wings
  • Dark markings
  • Two-inch wingspan

Nymphalis Californica

Also known as Nymphalis Californica, the California Tortoiseshell belongs to the Brush-footed family.

As part of the family, the California Tortoiseshell’s fore-legs resemble hairy stumps2.

This unique attribute sets it apart from other butterfly species.

California Tortoiseshell

Habitat and Distribution

California Tortoiseshell butterflies have specific preferences when it comes to host plants and habitats.

The butterfly can be found from British Columbia south along the Pacific Coast to as far as Baja California Norte, east to Montana, Wyoming, Colorado, and New Mexico.

The adults lay eggs exclusively on various species of wild lilac (Ceanothus). This is where the immature butterflies thrive.

Life Cycle of the California Tortoiseshell

Eggs and Caterpillars

The life cycle of the California Tortoiseshell starts with the adult butterflies laying their eggs.

Female adults specifically choose to lay their eggs on various species of wild lilac (Ceanothus) which act as the host plants for the immature butterflies1.

  • After hatching, the caterpillar stage begins.
  • Caterpillars feed on the host plant, developing quickly.

Pupa and Adult Butterfly

Once the caterpillar has completed its development, it forms a pupa to undergo metamorphosis1. During this stage:

  • The transformation into an adult butterfly takes place.
  • The California Tortoiseshell emerges as a fully-developed adult.

Features of the adult California Tortoiseshell:

  • Bright orange-brown wings2.
  • Dark markings on the wings2.
  • Two-inch wingspan2.

The adults play a crucial role in pollination, contributing to the overall health of their ecosystem.

Host Plants and Feeding Habits

Ceanothus and Snowbrush

California Tortoiseshell butterflies are known to be quite selective when it comes to their host plants.

Adults primarily lay their eggs on different species of wild lilac, also known as Ceanothus.

Snowbrush (Ceanothus velutinus) is one such species, often found in the canyon and high-altitude environments.

Defoliation and Larval Densities

These butterflies may occasionally cause defoliation, especially when larval densities are high.

As the larvae feed on their preferred host plants, they can strip the leaves off Ceanothus species.

Predators and Defense Mechanisms

The California Tortoiseshell, with its vibrant hues and fluttering flight, is not just a delight for butterfly enthusiasts but also attracts the attention of various predators.

Among the common predators of this butterfly species are birds such as ravens, which are adept at catching these colorful insects mid-flight.

Additionally, spiders, mantises, and other insectivorous creatures also pose a threat to both the adult butterflies and their larvae.

Defense Mechanisms

To counteract these threats, the California Tortoiseshell has developed several defense mechanisms.

One of the primary strategies is its ability to camouflage.

When perched, the mottled brown undersides of the butterfly’s wings allow it to blend seamlessly with its surroundings, making it less visible to predators.

This form of crypsis is particularly effective when the butterfly is resting on tree bark or amidst foliage.

Another defense mechanism exhibited by the California Tortoiseshell is its erratic flight pattern.

The unpredictable nature of its flight makes it challenging for avian predators to track and capture it.

This erratic flight, combined with its ability to rapidly accelerate, helps the butterfly evade capture and escape from potential threats.

Moreover, the caterpillars of the California Tortoiseshell also employ defensive strategies.

When threatened, the larvae can exhibit thrashing movements or release distasteful chemicals to deter predators.

These chemicals are often bitter and serve as a deterrent to birds and other would-be attackers, ensuring the survival of the caterpillar to the pupal stage.

Behavior and Migration Patterns

Population Explosions

The California Tortoiseshell butterfly is known for its occasional population explosions, which can lead to large numbers of butterflies migrating together.

These events are typically associated with an abundance of their primary host plant, the wild lilac (Ceanothus) species1.

Seasonal Migration

California Tortoiseshells are migratory butterflies but their migrations are not as predictable as some other species.

They undergo seasonal migration, which means they travel between different regions depending on the time of year:

  • Winter: They overwinter in sheltered, low-elevation areas
  • Spring: As the temperatures rise, they move up to higher elevations
California Tortoiseshell

Upslope Movement

Upslope movement2 happens when California Tortoiseshells follow the retreating snowline during spring.

This is because their preferred host plant, the wild lilac, is found in higher elevations after the snow melts.

In their upslope movement, the butterflies lay eggs on the wild lilac plants, ensuring the survival of the next generation.

California Tortoiseshell in North America

West Coast and Mountain States

California Tortoiseshell (Nymphalis californica) is a butterfly species commonly found in the West Coast and Mountain States, including locations such as Lassen Volcanic National Park.

Oregon and California are also home to this species.

They are known for their mass migrations, where thousands of individuals might travel between foothill canyons and high elevation locations.

Some features of the California Tortoiseshell are:

  • Orange and brown wings
  • Often mistaken for Monarch Butterflies
  • Favors wild lilac (Ceanothus) as host plants for their immature stage

East Coast States

Though primarily found in the West Coast and Mountain States, California Tortoiseshell may occasionally be spotted in East Coast States such as Vermont, New York, and Pennsylvania.

However, their presence in these regions is not as well-established and less common compared to the areas that experience mass migrations.

Notable Locations

Yosemite and Sequoia

California Tortoiseshell butterflies can be found throughout the Sierra Nevada, taking refuge in numerous National Parks.

In Yosemite National Park, visitors often spot these butterflies, especially during the summer months.

Hikers can witness the beautiful interaction between the tortoiseshells and the diverse plant life.

In Sequoia National Park, the sightings are just as frequent. The California Tortoiseshell butterfly thrives in a variety of habitats, such as forests, meadows, and shrub-covered areas within both Yosemite and Sequoia parks.

Kings Canyon and South Cascades

Kings Canyon National Park, adjacent to Sequoia, shares similar characteristics.

Here, California Tortoiseshells find a healthy habitat for migration and breeding.

Hikers exploring this region can enjoy the bustling activity of these captivating butterflies throughout the warmer months.

The South Cascades region, particularly Lassen Volcanic National Park, is also a hotspot for California Tortoiseshells.

They are often mistaken for the more famous Painted Lady butterfly, but their habits differ.

Where Painted Ladies migrate long distances, California Tortoiseshells tend to stay within the bounds of the local region.

Comparison of California Tortoiseshell and Painted Lady Butterflies:

Feature California Tortoiseshell Painted Lady
Migration Distance Shorter, regional migrations Longer, often transcontinental migrations
Preferred Habitat Sierra Nevada, South Cascades Various, including North America, Asia, Africa, and Europe
Appearance Orange with dark markings, smaller wingspan Orange with dark markings, larger wingspan

In summary, California Tortoiseshell butterflies can be spotted and enjoyed by hikers and nature enthusiasts in numerous National Parks and the South Cascades region.

They contribute to the natural beauty and biodiversity of these well-loved locations.

Comparison with Other Butterflies

Sexual Dimorphism

In the case of the California Tortoiseshell, sexual dimorphism is not easily noticeable.

Both males and females have similar bright orange-brown wings and dark markings, making them difficult to distinguish from one another1.

Monarch

Comparing California Tortoiseshell with other popular butterflies like the Monarch reveals some differences:

Feature California Tortoiseshell Monarch Butterfly
Family Nymphalidae Nymphalidae
Size 2-inch wingspan1 3.7 – 4.1 inches2
Color Bright orange-brown1 Orange, black, and white2
  • Caterpillars: While California Tortoiseshell caterpillars feed specifically on wild lilac (Ceanothus) species3, Monarch caterpillars rely on milkweed plants for sustenance2.
  • Pupae: Both butterflies undergo metamorphosis, developing into pupae before maturing into adults.
Male Monarch

Painted Lady

When contrasting the California Tortoiseshell with the Painted Lady, one can identify these differences:

Feature California Tortoiseshell Painted Lady
Family Nymphalidae Nymphalidae
Size 2-inch wingspan1 2 – 2.9 inches4
Color Bright orange-brown1 Orange, brown, and white4
  • California Tortoiseshell caterpillars prefer wild lilac3, while Painted Lady caterpillars thrive on a variety of host plants, such as thistles and nettles4.
  • Painted Ladies are often seen with a wingspan of up to 3 inches, making them slightly larger than the California Tortoiseshell14.

Conclusion

In conclusion, the California Tortoiseshell is a captivating butterfly native to the western United States, notable for its vibrant orange-brown wings and exclusive reliance on wild lilac as a host plant.

This species exhibits intriguing behaviors, including seasonal migrations and population explosions, and can be predominantly observed in regions like Yosemite and Sequoia National Parks.

Despite facing threats from various predators, the butterfly employs effective defense mechanisms, ensuring its survival and continued contribution to the region’s biodiversity.

Footnotes

  1. Pollinator of the Week: California Tortoiseshell Butterfly 2 3 4 5 6 7 8 9
  2. California Tortoiseshell – U.S. National Park Service 2 3 4 5 6 7 8
  3. https://blogs.oregonstate.edu/gardenecologylab/2018/01/10/pollinator-week-california-tortoiseshell-butterfly/ 2
  4. https://www.insectidentification.org/insect-description.php?identification=Painted-Lady-Butterfly 2 3 4

Authors

    by
  • 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.

    View all posts
  • 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.

    View all posts

12 thoughts on “Captivating California Tortoiseshell Butterflies: A Must-Know for Butterfly Enthusiasts”

  1. Thanks a lot for your reply… After examining images from the useful website “Butterflies and moths of Europe and North Africa” I discovered that its actually Nymphalis xanthomelas, or “The Yellow legged Tortoiseshell”…
    Yours: Mohsen Arooni, Tehran, Iran…

    Reply
  2. Hi Daniel,

    I believe that this is the Small Tortoiseshell Aglais urticae, which is common in Europe, but which also occurs all the way across Asia.

    Assuming I am correct about the species, the caterpillars feed on the common stinging nettle Urtica dioica and the small nettle <U. urens.

    The butterflies overwinter, often in houses or other buildings, and then come out in the spring, looking a bit worse for wear.

    Mohsen may not start to see caterpillars for a while, because the butterflies need to mate, lay eggs and the eggs hatch and grow a bit before the darkish, somewhat hairy caterpillars are noticeable on beds of nettles.

    I used to raise these butterflies myself when I still lived in England. It’s not easy picking stinging nettles every day for the caterpillars to eat. I used to use a plastic bag as a glove!

    Best wishes, Susan J. Hewitt

    Reply
  3. Hi Daniel,

    I believe that this is the Small Tortoiseshell Aglais urticae, which is common in Europe, but which also occurs all the way across Asia.

    Assuming I am correct about the species, the caterpillars feed on the common stinging nettle Urtica dioica and the small nettle U. urens.

    The butterflies overwinter, often in houses or other buildings, and then come out in the spring, looking a bit worse for wear.

    Mohsen may not start to see caterpillars for a while, because the butterflies need to mate, lay eggs and the eggs hatch and grow a bit before the darkish, somewhat hairy caterpillars are noticeable on beds of nettles.

    I used to raise these butterflies myself when I still lived in England. It’s not easy picking stinging nettles every day for the caterpillars to eat. I used to use a plastic bag as a glove!

    Best wishes, Susan J. Hewitt

    Reply
  4. Hi Susan…
    These are very similar and I’ve raised the small tortoiseshell too!… Ouch!…
    This one has a larger wingspan… Also, it has more spots on the forewing… Plus, there are no blue spots on the forewing margins…
    Thanks for sharing your experiences…

    Reply
  5. Dear Bugman…
    I can’t consider your reply as a scientific answer… I speak persian and common names like “Tortoiseshell” are not useful here… So perhaps knowing the scientific name (international standards) might be more helpful…?

    Reply
  6. Dear Mohsen,
    With all due respect, we realize our response to you was unscientific, because the fact of the matter is, we are not scientists. We have proudly announced on our website on numerous occasions that we are artists with no scientific backgrounds. While we try our best to properly identify submissions sent to us, the fact of the matter is that counting tarsi, dissecting butterfly genitalia (a skill that our favorite author Vladimir Nabokov possessed) and plotting wing veinage is well beyond the scope of our skills. Even within the scientific community, we find that experts in Crane Flies (Family Tipulidae) are often not much help when a person is trying to identify an Assassin Bug (Family Reduviidae) because in our 21st Century world, we have specialists with a narrow scope of expertise. Our website mission, and perhaps we should post our Mission Statement on our website, is “to assist the average person in developing an appreciation of the lower beasts, while doing what we can to correctly identify the family, genus, and occasionally the species of photos submitted to our site.” Sometimes it is not even possible for us to identify the family, and the order will have to suffice. Many of the Mites submitted to our site were merely identified as Mites before an Acarologist assisted us with the proper identifications. While we are sorry that you were disappointed in our unscientific answer, we did what we could, and it seems as though Susan came to your rescue with several possibilities for the proper species.

    Reply
  7. Dear Bugman…
    Forgive me.. I should have read the “About WTB”… Now I realize that we are all students… Learning from each other…
    After reading some books, I’m sure this butterfly is N. xanthomelas…
    Thanks for your informative reply…
    Yours… Mohsen Arooni
    Tehran, Iran…

    Reply
  8. Thanks for writing back Mohsen,
    Your letter has prompted us to try to concisely develop our mission statement, and we would also like to add that we promote a global community of tolerance.
    Have a wonderful day.
    Daniel

    Reply
  9. It’s a Small Tortoishell, which is very common. Note the white on the top tips of the upper wings, and the 3 black blobs.

    Reply

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