What Eats Monarch Butterflies: A Fascinating Look at Their Predators

Monarch butterflies are fascinating creatures known for their beautiful appearance and incredible migration patterns. However, they are also a critical food source for various predators, which play an essential role in maintaining a balanced ecosystem.

While monarch butterflies might have a natural defense mechanism with their bright colors, it doesn’t always deter predators. In fact, the striking appearance serves as a warning sign, signaling “Poison!” to potential threats, thanks to the toxins they acquire from milkweed plants during their caterpillar stage source. Despite this, some predators have developed a tolerance or immunity to these toxins and still consider monarchs a tasty meal.

Understanding the relationships between monarch butterflies and their predators not only provides fascinating insights into the natural world, but also helps us consider conservation efforts needed to maintain the health and balance of ecosystems in which they reside.

Monarchs as Prey

Monarchs, with their bright orange wings and unique patterns, are not only admired by humans, but are also a source of food for various predators. While they aren’t defenseless, their bright colors serve as a warning to potential attackers, indicating that they may not be a pleasant meal.

Although monarch butterflies have toxins in their bodies that deter several predators, some birds such as black-backed orioles and black-headed grosbeaks have developed a tolerance for these toxins. By ripping open the wings and avoiding the most toxic parts, they can feast upon the monarchs without any fatal consequences.

However, birds are not the only predators monarchs need to worry about. Spiders present a significant threat as they are capable of capturing them without ingesting their toxins. Spiders, like the crab spider, use their excellent camouflage abilities to blend in with their surroundings and ambush unsuspecting butterflies.

Mice are another predator that pose a risk to monarch butterflies, especially during their overwintering phase when they gather in large numbers in their wintering habitats. Mice can quickly adapt their feeding habits to consume large quantities of sleeping butterflies found on trees.

Praying mantids, despite their small size, can outmaneuver butterflies with lightning-fast reflexes. They use their spiked arms to grasp the monarchs and eat them, avoiding the wings containing the toxins.

Lizards, such as the anole, chase after adult monarch butterflies, juvenile caterpillars, and eggs, making them versatile predators in habitats where both types of prey are available.

In summary, here are some key predators of monarch butterflies:

  • Birds (black-backed orioles and black-headed grosbeaks)
  • Spiders (crab spiders)
  • Mice
  • Mantids (praying mantids)
  • Lizards (anole)

Each predator mentioned above uses different strategies to catch and consume monarch butterflies, showing the wide range of threats these beautiful creatures face in their natural environments. To help protect the monarchs, you can contribute by creating safe habitats in your garden and supporting conservation efforts that preserve their natural environments.

Predators in Different Life Stages

To better understand the threats faced by monarch butterflies at different stages of development, let’s explore the various predators that target them during the egg, caterpillar, and adult butterfly stages.

Egg Predators

When it comes to their eggs, monarch butterflies face several predators. Some common ones include:

  • Ants
  • Flies
  • Wasps

These insects primarily feed on the monarch eggs, causing a decrease in the population of hatched caterpillars.

Caterpillar Predators

As the eggs develop into caterpillars, a new set of predators emerges. Monarch caterpillars have to beware of:

  • Birds
  • Spiders
  • Lizards
  • Mice

Take note of birds particularly the black-backed oriole and the black-headed grosbeak. They are known to consume large quantities of monarch caterpillars. Spiders and lizards, on the other hand, can ambush caterpillars and have them as their meal.

Adult Butterfly Predators

When monarch caterpillars finally transform into adult butterflies, they still face threats from predators which include:

  • Birds
  • Spiders

Birds, such as the black-backed oriole or the black-headed grosbeak, continue to pose a danger. They have developed the ability to tolerate the toxins present in adult monarch butterflies, allowing them to consume them with few ill effects.

Spiders, however, use a different tactic. They use their webs to trap the adult butterflies, feeding on them once they’re caught.

When understanding the life cycle and threats faced by monarch butterflies, knowing the predators at each stage of development can help you have a more comprehensive perspective on this beautiful and fascinating creature.

Chemical Defense and its Limitations

Monarch butterflies are known for their ability to store toxins from the plants they consume as caterpillars, with milkweed being the most well-known of these plants. These toxins, which are called cardenolides, make the monarch butterfly poisonous to most predators. But, there are some limitations to this defense mechanism.

One significant limitation is that not all species of milkweed contain the same concentration of cardenolides. For example, the common milkweed has lower levels of toxins compared to other species. Consequently, the toxicity of a monarch butterfly may vary depending on the type of milkweed it consumed in its larval stage.

Despite their poisonous nature, some predators have developed a resistance to cardenolides. Two notable examples are the black-headed grosbeak and the black-backed oriole. These birds have evolved mechanisms to metabolize and tolerate the toxins.

Here’s a summary of the points discussed:

  • Monarchs have a chemical defense due to the ingestion of milkweed during their caterpillar stage.
  • Cardenolides are the toxins found in milkweed and make monarch butterflies poisonous to predators.
  • Chemical defense has limitations, including the varying levels of cardenolides found in different milkweed species.
  • The black-headed grosbeak and black-backed oriole have evolved resistance to the toxins present in monarch butterflies.

Impact of Predation on Monarch Population

Monarch butterflies are an iconic species in North America, known for their incredible migration from Canada and the United States to Mexico. However, they face several threats such as predation, habitat loss, and climate change that have led to a decline in their population.

Predators play a significant role in monarch butterfly populations. Various species of birds, insects, and small mammals feed on monarchs throughout their life cycle. For example, birds like orioles and grosbeaks prey on adult butterflies, while wasps and ants may target monarch eggs and larvae.

Habitat loss is another factor affecting monarchs. Their primary food source, milkweed, has been declining throughout their breeding range. It is essential for the growth and development of monarch caterpillars. The loss of milkweed plants due to agriculture, urban development, and pesticide use has made it more challenging for monarchs to find suitable habitats for laying eggs and feeding.

Monarch butterfly populations are also susceptible to climate change. Unpredictable weather patterns, such as heavy rains or extreme temperature fluctuations, can harm their migration and breeding patterns. The delicate balance of their migration from North America to Mexico and back can be disrupted by changing climate conditions, affecting their survival rates.

As you can see, predation, along with habitat loss and climate change, has significant impacts on the monarch butterfly population. Efforts to conserve their habitats and create safe spaces that can support their migration are essential to help these impressive insects thrive in the future.

Monarch Butterflies and Parasites

Monarch butterflies are beautiful creatures, but they also face challenges from parasites. One of the most well-known parasites affecting these butterflies is Ophryocystis elektroscirrha. This parasite invades the body of the monarch and can cause deformities, decreased lifespan, and reduced ability to reproduce.

This parasite is not the only threat to the health and survival of monarch butterflies. They may also encounter parasitoids, which are organisms that kill their host as they develop. This is different from a parasite, which generally lives off the host without killing it.

Here’s a comparison table:

Factor Parasites Parasitoids
Host Lifespan Usually shorter Kills the host
Effect on Host Depletes energy Host used as food
Examples Ophryocystis elektroscirrha Tachinid flies

Remember to be aware of these threats facing monarch butterflies when taking steps to support their population. Planting appropriate host plants, like milkweed, can provide the food and habitat they need to thrive.

To help protect and preserve these iconic creatures, consider joining local conservation efforts or participating in citizen science projects. By working together, you can make a difference in the lives of these beautiful and vital pollinators.

Insects That Mimic Monarchs

Some insects have cleverly evolved to resemble monarch butterflies, helping them avoid predators. You might be surprised by the variety of insects that take on this appearance.

For instance, the viceroy butterfly is strikingly similar to the monarch in color and pattern. By mimicking the appearance of the unpalatable monarch, the viceroy butterfly gains protection from predators that avoid monarchs due to their toxic taste. Even though viceroys are not toxic themselves, their resemblance to monarchs is enough to deter many predators.

Another example is the queen butterfly, which also displays orange and black coloration, similar to the monarch. However, you can distinguish queen butterflies from monarchs by their smaller size and lack of distinctive black veins on their hindwings. Like the viceroy, this mimicry helps to protect the queen butterfly from being eaten by predators.

In addition to butterflies, some caterpillars also resemble monarchs to avoid predators. The swallowtail caterpillar, for example, can change its appearance to resemble the toxic monarch caterpillar, which feeds on milkweed, a poisonous plant. By mimicking this toxic species, the swallowtail caterpillar avoids being eaten by predators that have learned to avoid monarchs.

Here’s a quick comparison of these insects:

Insect Mimics Monarch Distinguishing Features
Viceroy Butterfly Yes Similar pattern, slightly smaller than monarch
Queen Butterfly Yes Smaller, lacks black veins on hindwings
Swallowtail Caterpillar Yes Changes appearance to mimic toxic monarch caterpillars

While these examples showcase just a few insects that mimic monarchs, they demonstrate the clever ways nature has evolved to help protect these creatures from predators. By closely resembling the unpalatable monarch butterfly, they increase their chances of survival in their natural habitats.

How Monarchs Avoid Predators

Monarchs have developed various strategies to protect themselves from predators. One such approach is camouflage. By resembling leaves or blending in with their surroundings, monarchs can avoid being easily detected by predators like birds and insects.

Apart from camouflage, migration plays a crucial role in their survival. Monarchs are known to make two-way migrations similar to birds. By traveling south in search of warmer climates when winter arrives, they escape harsh weather and predators that cannot survive colder temperatures.

The ecosystem also has a role in how monarchs elude predators. Monarch caterpillars feed on milkweed plants, which contain toxic compounds. When the caterpillars transform into butterflies, they retain these toxins in their bodies, making them unappetizing to potential predators. Predators often associate the bright colors of the monarch with their unpleasant taste and tend to avoid them.

Some examples of Monarchs’ strategies include:

  • Blending in with leaves or bark to avoid detection
  • Migrating to different regions to escape predators and adverse weather conditions
  • Retaining toxic compounds from milkweed plants as a defense mechanism

By employing these strategies, you can understand how monarch butterflies successfully navigate their environment and avoid harmful encounters with predators.

Human Influence on Monarch Predation

In your garden, various elements can impact monarch butterflies and their survival, such as the use of pesticides and herbicides. Human activities can indirectly contribute to monarch predation, and being aware of such effects can help protect these amazing creatures.

Some gardeners may unknowingly harm monarch populations by using pesticides like neonicotinoids. These chemicals are toxic to butterflies and can increase their vulnerability to predation. To reduce reliance on such chemicals, consider implementing integrated pest management practices that are more targeted and less harmful to non-target organisms like monarchs.

Herbicides are another potential threat to monarchs in your garden. These chemicals can eliminate the plants that serve as crucial food sources for monarch caterpillars, such as milkweed. Loss of habitat due to herbicides may lead to reduced monarch populations and increased predation pressure. Instead, try using organic or manual weed control methods to preserve these essential host plants.

By being mindful of the products and practices employed in your garden, you can make a positive impact on monarch butterfly populations. Consider the following tips to minimize negative effects on monarchs:

  • Use targeted and eco-friendly pest control methods.
  • Avoid using neonicotinoids and herbicides that harm monarch caterpillars and their host plants.
  • Plant native milkweed species to provide essential food and habitat for monarch caterpillars.

By adopting these practices, you can help protect monarch butterflies from increased predation and support a healthier ecosystem in your garden.


In conclusion, monarch butterflies face various predators in their life cycle. As caterpillars, they are primarily consumed by birds, spiders, and ants. To aid in their defense, these caterpillars feed on milkweed, as the toxins present in the plant make them taste unpleasant to their predators.

In the adult stage, monarch butterflies are still vulnerable to predation. Birds, such as grosbeaks and orioles, are some common predators that prey on monarchs. To deter these threats, the bright orange and black coloration on the butterflies’ wings signals their unpalatable taste, a result of their milkweed consumption.

Additionally, it’s worth noting that several animals rely on camouflage and mimicry to avoid becoming a meal for predators. For instance, the viceroy butterfly closely resembles the monarch butterfly in appearance, which helps it avoid being targeted by its own predators.

Protecting monarch butterflies and their habitats is crucial for maintaining their population. By conserving their food sources, particularly the native milkweed, we can help ensure their survival and the continuation of their incredible migratory journey.

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 – What Interrupted the Monarch Metamorphosis???


Location: Louisiana
April 7, 2012 2:18 pm
I have monarch caterpillars in my butterfly garden but they all seem to have a problem.Four of them climbed up to my fence and started making their chrysalis then just stopped soon after they split. I am under the understanding that this should only take 10 minutes. I am starting to think they have some kind of parasite but have no idea what to do about it.
Any help would be appreciated. I have a 3 year old that is really excited about them and I just don’t know what to do.
Signature: Thank You

What killed the Monarch???

Many caterpillars have internal parasites that prevent the insect from maturing, but we are unaware of any wasps or flies that prey upon Monarch Caterpillars.  We have seen predators like Predatory Stink Bugs kill Monarch Caterpillars, and the result of the predation looks similar to this since Stink Bugs suck the fluids from the body of the caterpillar.  We are sorry we have no advice to offer.  Perhaps you want to create a habitat for the caterpillars to undergo metamorphosis like this person has done.

Letter 2 – Purchase native milkweed for Monarch Caterpillars


Subject:  Monarch Caterpillars
Geographic location of the bug:  West Los Angeles
Date: 06/22/2019
Time: 04:37 PM EDT
Your letter to the bugman:  Hi Bugman,
Thought you’d enjoy seeing these youngsters.  By the way, I’ve replaced all the tropical milkweed in my yard with native plants.
How you want your letter signed:  Jeff Bremer

Early Instar Monarch Caterpillars

That is awesome Jeff.  Can you tell us whether you planted seeds or plants? and provide us with your source for native milkweed?

I bought the plants through Monarch Watch: https://shop.milkweedmarket.org/

Letter 3 – Monarch Metamorphosis in Elyria Canyon Park


Subject:  Monarch Emerges from Chrysalis
Geographic location of the bug: Elyria Canyon State Park, Mount Washington, Los Angeles, California
Date: 07/09/2021
Time: 8:51 AM PDT
Your letter to the bugman:  Dear Readers,
Last week Daniel informed you that while hiking in Elyria Canyon Park as post-operative knee therapy, he found a Monarch Chrysalis and Caterpillar on native Aesclepias eriocarpa.  Every day or two Daniel had been hiking back to check out the progress and yesterday the chrysalis appeared noticeably darker.

Monarch Chrysalis Day 10

Then this morning at 7:45 AM, the much awaited moment of translucence and the pattern of the wings showing through the exoskeleton.  Daniel sat on the bench to text the images to a few folk and then he laid down in the shade and listened to the birds, and an hour later, he realized that though he had missed the actual eclosion, he was still able to experience the mystery of metamorphosis and to view the helplessness of the newly transformed adult Monarch whose wings had not yet hardened and it was not yet able to fly.

Monarch Chrysalis Day 11

Despite missing the actual eclosion, Daniel was still witness to the hatchling testing out its strange new proboscis and auxiliary mouthparts.

Eclosion one hour later

Daniel writes:  “This new imago, though helpless, was adapting to its new vision thanks to the transformation of the visual sensation through complex compound eyes.  For about a half an hour I watched the adult Monarch feeling the breeze and testing the use of its new muscles in preparation for its maiden flight.  When I got close to take an image it was obvious the creature sensed me and potential threat because it appeared to quiver and to cower.  Not wanting my presence to interfere in the success of the transformation, I left thinking I might check up on it later in the afternoon, and to collect the remains of the exuvia.  I did note that there were no blossoms on the milkweeds in the patch.  All the blossoms seem to have withered and I pondered how much more successful a first flight would be after a first meal of milkweed nectar.  As I started my hike this morning, on my way into the canyon I watched an adult Monarch taking nectar from the blossoms of a patch of geraniums, but I reacted too slowly to get an image with the magicphone.”

Close-up of newly eclosed Monarch


Letter 4 – Monarch Migration: Beating the Weather


Subject: monarchs
Location: Westhampton Beach, NY
November 13, 2016 8:47 am
Dear Bugman,
I planted lots of butterfly weed in my yard & had so many monarch caterpillars this year! But now it is cold here in the northeast (east end of Long Island, NY) and I still see some. The problem is, the plants are dying and the caterpillars don’t have much to eat. Is there a way to save the larvae? There is one chrysalis hanging on a dead leaf. You can already see the wings inside. Will this hatch successfully & fly south? Thanks.
Signature: Elaine

Prepupal Monarch Caterpillar
Prepupal Monarch Caterpillar

Hi Elaine,
Alas, we cannot state with any certainty that your soon to emerge Monarch will successfully complete its migration voyage.  In nature’s effort to preserve populations, and because of the uncertainty of weather, insects may continue to reproduce past the time that they would complete metamorphosis before inclement weather begins.  From year to year, that date changes.  Like you, we will hope for the best.  If you cannot feed the larvae on milkweed, we don’t think your existing caterpillars will survive.

Thanks so much for your quick response.  I’ll see if I can find some local “weed” to feed them!

Letter 5 – Monarch Ovipositing


Subject: Daniel – Monarch Butterfly Oviposition
Location: Hawthorne, CA
November 11, 2012 10:54 pm
Hi Daniel,
Got these photos today of a lovely Monarch butterfly. Just wanted to share them with you.
Signature: Thanks, Anna Carreon

Monarch Ovipositing

Hi Anna,
Congratulations on your marvelous documentation.  Recently we have been noticing many Monarch Butterflies migrating across the grounds at Los Angeles City College, and perhaps we will propose that some milkweed be planted as part of the new campus landscaping that is supposed to include native plants.  This female Monarch has curved her abdomen in the act of oviposition, however, we are unable to make out an egg in either of your images.  Monarchs lay eggs singly on the leaves of milkweed, a behavioral pattern that is followed by many butterflies.  Moths on the other hand often lay eggs in clusters, though again, the style of oviposition does vary from species to species.  Does that species of milkweed keep its leaves all winter?  We hope the developing caterpillars will have a winter food source since previous Monarch Caterpillar images we received from you were a bit earlier in the year.

Monarch Ovipositing

Hi Daniel,
Thanks very much.  I think it would be a good thing for you to propose the planting of some milkweed at the college.  My Monarch spent almost twenty minutes yesterday back and forth around the milkweed plants ovipositing.  Unfortunately my little Sony Cybershot can’t pick up the actual egg.  Oh, for a better camera!  This species of milkweed does keep its leaves all winter.  I hope her caterpillars (should any of them make it as there are wasps, large milkweed bugs and small milkweed bugs aplenty out there right now) will be able to develop into viable butterflies.  This oviposition is later than last year and I remember that at least one butterfly did not develop correctly.  One wing was horribly deformed.  Keeping my fingers crossed.  I think the cold weather must play a part.


Letter 6 – Monarch Project: Caterpillar, Crysalids, and Butterfly


Monarch Project
Dear Bugman,
I thought I’d share with you this photo of my 6-year-old grandson’s butterfly project. The monarch emerged this morning from the first of 46 chrysalises (with more to come). Thanks for your great website!
Nancy Codere
Cumberland, ME

Hi Nancy,
We only wish your letter had included a more detailed description of what the Monarch Project is. We are guessing your grandson collected Monarch Caterpillars off of milkweed plants and kept them in a cage to observe the metamorphosis.

Dear Daniel,
I thought I’d share with you this photo of my 6-year-old grandson’s butterfly project. He collects the caterpillars from a stand of milkweed in back of our house and keeps them in a 10-gal. terrarium with screen cover. Everyday 3 to 4 fresh milkweed stalks are added as food. When the caterpillars are ready, most crawl to the cover to begin their metamorphosis (an occasional one will hang from a milkweed stalk and make his transformation there). When a chrysalis turns black (it’s actually clear but the unborn butterfly’s coloring shows through), we suspend the screen cover from a hook on the ceiling to observe the critter’s emergence. The monarch in this picture emerged this morning from the first of 46 chrysalises (with more to come). Thanks for your great website!
Nancy Codere
Cumberland, ME

Letter 7 – Monarchs are breeding in Elyria Canyon Park


Subject:  Monarch Caterpillar and Chrysalis on Indian Milkweed
Geographic location of the bug: Elyria Canyon State Park, Mount Washington, Los Angeles, California
Date: 06/29/2021
Time: 8:30 AM PDT
Your letter to the bugman:  Dear Readers,
As part of physical therapy rehabilitation for knee surgery, Daniel has begun hiking again, and this morning he was pleased to find first a Monarch Chrysalis and then a Monarch Caterpillar feeding on Kotolo or Indian or Wooley Milkweek,
Aesclepius eriocarpa, in Elyria Canyon State Park.

Monarch Caterpillar
Monarch Chrysalis

Letter 8 – Monarchs hatch from Christmas Tree


Christmas tree
January 9, 2012
Location:  This is in Jacksonville, Florida, on the banks of the beautiful St Johns River.
Hi Bugman,
I don’t remember if I sent this photo to you but even if I did, it’s worth a rerun.
Happy New Year,

Monarchs Hatch from Christmas Tree

Happy New Year Lane,
What a marvelous follow-up to your awesome Monarch Chrysalis Christmas Tree.  Thanks so much for the update.

Letter 9 – Monarchs are Migrating through Mount Washington. Tagging Migrating Monarchs.


Monarchs are Migrating in Mount Washington
Location: Mount Washington, Los Angeles, California
November 11, 2013
Yesterday while helping our friend Lisa Anne determine which plants should stay and which should be removed from her newly purchased Mount Washington home, we noticed two Monarchs flying through her yard and over Elyria Canyon Park. This morning while running errands, we noticed four more Monarchs. We suspect the Monarchs are seeking wintering grounds either to the north or to the south in Mexico, and they are passing through Los Angeles to get there. We need to do some gardening today, but we will provide an update with a new photo if any Monarchs alight on the lantana or the zinnias currently blooming in the garden.

Female Monarch
Female Monarch takes nectar in the WTB? garden in 2012

Ed. Note:  We contacted our neighbor, Julian Donahue, about the migration and we had a nice chat on the phone regarding migration and tagging of butterflies.  We mentioned that many of our readers raise Monarchs and tag them so that they know which butterflies they raised, including Dori Eldridge from Naperville, Illinois.  We thought we had an old posting where green paint was used to mark a Monarch, which Julian discouraged as color blind individuals cannot see red or green.  Julian provided us with a photo of a tagged Monarch as well as some additional information on migrating butterflies.  If you encounter a tagged Monarch, please report it using the website provided on the tag.

Tagged Monarch
Tagged Monarch

Daniel, you and I discussed the Monarchs and Painted Ladies on the phone: the former are drifting around (natives and possible migrants arriving for the winter), while the Ladies are residents–they don’t migrate until around April, if at all. I’ll be posting a notice about Monarchs that were tagged in Washington state on the LepSoc Facebook page.
I’m attaching the photo I promised of a tagged Monarch from Washington, which has on it the e-mail address to report sightings or recoveries.


Letter 10 – Newly Emerged Male Monarch visits WTB?


Subject:  Newly Emerged Male Monarch
Geographic location of the bug:  Mount Washington, Los Angeles, CA
Date: 08/25/2018
Time: 11:30 AM EDT
Daniel was relaxing in the front yard when this Monarch flew past, seemingly struggling with flying, and it landed on the ground where Jennifer began to take some photos and video with her cellular telephone.  Daniel got the camera and by that time, Jennifer also noticed that something was not right, and the Monarch had flown to a laurel sumac.  Daniel had already suspected that perhaps what was wrong was that this was a newly eclosed Monarch that had not yet gotten used to flying.  The pristine quality of the wings and the fact that it rested on the sumac for about a half an hour, opening and closing its wings before flying off, both support that suspicion.  According to BugGuide:  “Males have scent-scale patches on hindwings, prominent when wings are open, and just possible to see when wings are folded” and this individual flashed his scent-scale patches for the camera.

Male Monarch


Letter 11 – Nivosus Monarch


Nivosus Monarch
July 27, 2009
I do alot of butterfly and dragonfly photography in the summer and was surprised by this butterfly when we came across it. I’m by no means an expert on identification, but it appeared to me to be an odd colored monarch. I looked for information online and read about nivosus or white monarchs. My understanding is that the color difference is caused by a recessive trait and affects less than 1% of the US monarch population. I think this is what I have here, can you confirm it for me? If this is rare it may have some interest for your readers.
SE Wisconsin

Monarch Butterfly:  Nivosus or just faded???
Nivosus Monarch Butterfly

Hi Cindy,
Your Monarch Butterfly surely is a light individual, but it is not as white as the individual pictured on the Monarch Watch website illustrating the paper written by Lawrence Gibbs and Orley R. Taylor
.  That individual is truly white.  We believe your individual may have a genetic predisposition for lightness, but we also believe it shows evidence of worn wings, perhaps due to old age and perhaps due to traveling long distances.  As the wing scales are lost, the coloration of the butterfly appears more faded.  It is also possible that this might be an intermediate coloration between the usual orange Monarch and the pale Nivosus Monarch.  Perhaps an expert will be able to chime in and solve the question.

Thanks so much for your response.  I followed up with your link to Monarch Watch and sent them an email and download of the photo.  I received a response from them which also included some additional links within their site.  Although they would need to see the actual specimen for 100% accuracy, they said it definitely appears to be a nivosus.  After doing some reading on the site and looking at more photos, it appears there is a range of nivosus coloring such as the one I found to the very black and white which you noticed at the top of the article.

Letter 12 – Parasitized Monarch Chrysalis


Subject:  Chrysalis in SE Michigan
Geographic location of the bug:  SE Michigan
Date: 10/19/2018
Time: 11:54 AM EDT
Your letter to the bugman:  These (2) are in my yard.  The immediate area is a vernal marsh area, with swamp milkweed.  They are not on the milkweed, but it is close by.
How you want your letter signed:  Bill Jones

Parasitized Monarch Chrysalis

Dear Bill,
Physically, this appears to be a Monarch chrysalis, however the color is not normal.  A normal Monarch chrysalis is bright green with gold flecks, and as it nears the time for the adult to emerge, the orange wings appears through the exoskeleton.  Your chrysalis appears to have fallen prey to a parasite, probably a Tachinid Fly like the chrysalis pictured on Monarch Lover

Letter 13 – Queen Caterpillar, Not Monarch


Subject: Odd Monarch Butterfly Caterpillar
Location: Hawthorne, California
January 4, 2015 6:47 pm
I spotted the odd markings on the caterpillar on top earlier today, so took a few quick shots. Imagine my surprise when I got them on the computer, zoomed in, and noticed that the rear antennae aren’t where they are supposed to be! I’m as sure as I can be that it is a Monarch Butterfly Caterpillar and that something has gone wrong. Have you ever seen this type of mutation? I’ve seen them with different markings, but not this noticeable and certainly not with rear antennae so high up on the body.
Signature: Thanks, Anna Carreon

Queen Caterpillar (above) and Monarch Caterpillar
Queen Caterpillar (above) and Monarch Caterpillar

Dear Anna,
We are thrilled to be able to tell you this exciting news.  The reason this caterpillar looks like a Monarch Caterpillar is that it is a related “royal” species in the same genus, the Caterpillar of a Queen.  Adult Queen Butterflies are darker than Monarch Butterflies and their markings are not as pronounced, but they look very similar.  Queen Butterflies also have habits very similar to those of Monarchs, including food plants, but Queens do not migrate.  Congratulations on your new species sighting.

Queen Caterpillar (upper right) and Monarch Caterpillars
Queen Caterpillar (upper right) and Monarch Caterpillars

Oh, my!  Well, I am also thrilled!  I was sure it was some sort of mutation.  I guess I really should stop believing I know what I am talking about and leave stuff like this to those who have more experience and know better.
Thank you so much for making my day!

Letter 14 – Quite possibly a Tachinid Fly and Monarch Chrysalis


Subject: What’s This Fly on Cilantro Blooms?
Location: Hawthorne, CA
January 10, 2014 3:38 pm
Hi Daniel,
We wish you and yours a happy, healthy New Year filled with love. I was out in the back today and noticed this fly on the cilantro blooms. Can you help with identification? It’s most likely very common, but boy is it ugly!
Also, we still have one lonely Monarch Butterfly caterpillar chomping away on the Mexican Milkweed. We haven’t been able to locate any chrysalides this cycle, but are sure they’re out there somewhere!
Signature: Thanks, Anna Carreon

Looks like a Tachinid Fly to us
Looks like a Tachinid Fly to us

Hi Anna,
Happy New Year to you as well Anna.  We are still awaiting the sprouting of those cosmos seeds.  The conditions of our northern exposure garden often result in delays in seed sprouting.  This really looks like a Tachinid Fly to us, and we will attempt to locate a matching photo on BugGuide tomorrow.  Tachinid Flies in the family Tachinidae are important natural biological control agents, because according to BugGuide:  “larvae parasitize insects (and a few other arthropods, incl. millipedes, spiders, scorpions); adults may take nectar” and caterpillars are one of the primary hosts.  You might have photographed the reason you have noticed fewer Monarch Caterpillars this year.

Update:  January 12, 2014
This Tachinid Fly from our archives looks somewhat similar and the antennae look like those on this unidentified Tachinid Fly on BugGuide.

Hi Daniel,
Somehow I remember you telling me that you did have some sprouting of the cosmos seeds.  I thought it was rather odd as they don’t usually surface until spring.  We hope you have success with them!
I think your identification of this as a Tachinid fly is correct, but it’s different from the ones we’ve seen in past.  I also want to let you know that a Monarch chrysalis has been spotted!  I know it wasn’t there when I closed up the shed mid-afternoon yesterday and surely would have spotted the caterpillar crawling up the side of it were that happening while I was there.  The chrysalis is a good 12 feet away from any milkweed plant, and is about 6′ high on the front of the shed, just above the door.  Such an exposed area!  We’ve also had paper wasps building nests nearby in the past, so will have to keep a good eye out for them and try to discourage that activity for a while.

Monarch Chrysalis
Monarch Chrysalis

Thanks for the update Anna.

Letter 15 – Southern Monarch Caterpillar from Brazil


Danaus erippus
Location: Londrina-Paraná-BRASIL
April 9, 2012 2:52 pm
Danaus erippus
Signature: Eduardo Lucof

Southern Monarch Caterpillar

Dear Eduardo,
Thank you for submitting your four caterpillar photos from Brazil.  We are posting the Southern Monarch Caterpillar immediately and we will attempt to post others if time permits.  Sadly, you didn’t provide us with any information except a species name.  We are linking to the Tree of Life website for photos of the adult Southern Monarch and to the National Geographic website for a photo of the Southern Monarch Caterpillar.

Letter 16 – Tachinid Fly Parasitizes Monarch Caterpillar


Subject: Emerging Tachinid fly and RIP monarch
Location: Minneapolis, MN
June 4, 2012 10:17 pm
We found a nice monarch caterpillar this weekend and brought it home for our children to watch this lifecycle. Unfortunately, we got to see this Tachinid fly emerge and show us a new life cycle. I assume this is Lesperia archippivora. The caterpillar was found in Minneapolis.
Signature: Daniel

Tachinid Larva vacates Monarch Caterpillar husk

Dear Daniel,
Thank you for sending in this awesome documentation.  It appears as though the maggot vacates the carcass of the Monarch Caterpillar and pupates elsewhere.  We wish the enlargement of the Tachinid Maggot had better clarity.

Pixilated Tachinid Larva, possibly species specific to the Monarch



Letter 17 – The Monarchs have landed!!!


monarchs on my milkweed
I still like the milkweed beetles more, but this is the initial reason I decided to let the milkweed grow rampant in my garden (despite my neighbor’s request that I pull it all in the spring). I hope these are indeed real monarchs, please let me know if they aren’t.

Hi John,
The Monarchs have landed. We hope you get caterpillars.

Letter 18 – Viceroy compared to Monarch and Mating Cabbage Whites


Viceroy vs Monarch & buglove with two cabbage butterflies
I always enjoy checking your site for the newest listings. Attached are two photos that you might want in the files. The first is a stitched pair – on the left is a Viceroy and on the right is a Monarch. Having them side by side makes comparing the two much easier. The second photo is of a pair of cabbage butterflies mating. Perhaps it could be added to the bug love page. Enjoy,

Hi Tetrazole,
The Viceroy and Monarch comparison is a much welcomed addition to our site as is the image of the mating Cabbage White Butterflies. Readers should take note of the black postmedian band on the lower wing of the Viceroy which is the most obvious distinguising feature for ensuring proper identification of the species.

Letter 19 – Viceroy: Monarch Mimic


Viceroy? Male or female?
First, I love your web site! Fantastic! I may have to catch and identify the spiders and other critters that seem to like my apartment now that I have a way to identify them. Secondly, today I had a delightful surprise as I walked out to my motorcycle after work. As I approached, this lovely butterfly landed on the side view mirror of my bike. She(?) patiently waited and slowly flexed her wings in the sun while I dug out my camera phone to get these unfortunately blurry pictures. My question is whether this is a Monarch or a Viceroy? My impression is that it is a Viceroy, due to the horizontal black vein across the lower section of the hind wings. Are there other easy ways to conclusively distinguish the Monarch from the Viceroy? And finally, if this is a Viceroy, is there a visual way to distinguish the sex (like the Monarch male’s black spots?)
David Lauridsen
Cincinnati, OH

Wow David,
What a nice letter. Yes, this is a Viceroy, Limenitis archippus which is very closely related to the Red Spotted Purple and White Admiral which it does not resemble. It was long thought that Viceroys tasted good to birds and Monarchs did not, but our Butterflies Through Binoculars Book by Jeffrey Glassberg says that “Recent evidence suggests that, at least in Florida, Viceroys are also distasteful to birds. Presumably, a greater number of similar-looking unpalatable individuals in an area results in a faster learning curve for birds, sparing butterflies.” Also according to Glassberg: “Viceroys are smaller than Monarchs and they often glide on flat wings while Monarchs and Queens sail with their wings in a V.” We can’t really tell you how to easily distinguish male from female Viceroys, but we are amused you thought your specimen was female. We presume it is because motorcycles are chick magnets.


  • 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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8 thoughts on “What Eats Monarch Butterflies: A Fascinating Look at Their Predators”

  1. According to Dr. Fred Urquhart, this happens when a strand of silk wraps around the caterpillar as it makes its silk pad. He wrote “International Traveler, The Monarch Butterfly”. There is some doubt about this being the only reason as some people, like the reader that wrote here, find a large percentage of them in a small group to whom this will happen. There are many wasps and flies, both parasitoids and predators, that eat Monarch caterpillars and pupae. http://www.butterflyfunfacts.com/butterflyparasitoids.php http://www.butterflyfunfacts.com/caterpillarpredators.php None of them cause a problem like these that only partially pupated.

    • Thank you so much for this informative comment. It would be interesting to learn why there is such a preponderance of this phenomenon in this particular population of Monarch Caterpillars. The silk strand theory would explain an isolated event, but not the repetition that has been observed by the person who submitted this photograph.

  2. Daniel will forgive me if I offer a little clarification about Monarch overwintering sites on the West Coast. A fascinating and informative paper by John Lane, 1993 (“Overwintering Monarch Butterflies in California: Past and Present”), in Biology and Conservation of the Monarch Butterfly (Natural History Museum of Los Angeles County, Science Series No. 38, pp. 335-344) summarized our knowledge about where western Monarchs spend the winter. Just over 200 overwintering sites have been reported in California, from Mendocino to San Diego Counties (about 80% of the California coast), with one overwintering site reported in Ensenada, Baja California (the only site known in western Mexico). (There are isolated inland observations from Kern and Inyo Counties, California.) Although I am not aware of any overwintering sites on the California Channel Islands, two Monarchs tagged at the overwintering site in Leo Carillo State Beach, Los Angeles Co., on 26 Dec. 1985 were recovered during the spring dispersal from that site on Santa Cruz Island, Santa Barbara Co., on 5 February 1986 (“Spring Migration of Monarch Butterflies in California” by C.D. Nagano et al., pp. 219-232 in the same volume).

    Since Monarchs reproduce in, and adults are found year-round in, at least Orange and Los Angeles Counties in southern California, the butterflies we see here in November and through the winter may be a mixture of residents and migrants–there is no way to distinguish between them in the field–unless the Monarch has been tagged! (Chemical analysis of a specimen, however, could determine which species of milkweed the butterfly fed upon as a caterpillar, thus identifying the butterfly’s origin within the distribution of that particular species of milkweed. The results of such an analysis may not be conclusive, however, because many milkweeds are cultivated for ornamental purposes outside their normal range, especially the tropical Asclepias curassavica here in Southern California.)

  3. There is a nasty bacterial infection all too common in Monarch caterpillars–actually there are two. http://monarchparasites.uga.edu/whatisOE/ describes the parasite which can kill them in the chrysalis. This FAQ from the old Garden Web site does a nice job of describing the bacterial (Pseudomonas) and viral (Nuclear Polyhedrosis Virus) causes of ‘Black Death’ of monarchs. Hope that helps!

  4. The metamorphosis of butterflies is one of those natural wonders that every child should witness along with seeing how orb weavers make their webs and baby mantises emerge from the egg case. Back in the 50’s my grammar school teachers made sure the kids saw these things. I certainly hope that the vogue for electronic devices rob children of the first hand experience of nature.


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