Is Mourning Cloak Caterpillar Poisonous?

For those looking to breed beautiful mourning cloak butterflies, it is important to know that their caterpillars have stinging hair. Let’s learn more about it and what to do if you get stung.

Nymphalis antiopa, or mourning cloak, is a large butterfly found in North America. These beautiful butterflies live for almost ten months, more than most others. 

The larval stages of mourning cloak butterflies are known as spiny caterpillars. These caterpillars are known for their spiny body. When these spines come in contact with human skin, they can cause pain, severe infection, blistering, and other problems. 

So, it’s better to avoid touching these fuzzy caterpillars. In this article, we will talk more about these caterpillars.

What Does the Mourning Cloak Caterpillar Look Like?

Mourning cloak caterpillars are 2 inches long (on average) and have a very striking appearance.

These caterpillars have black bodies, with reddish-orange dots found in every segment of their body. 

Their entire body is covered with hair and black-colored spines with white dots on them.

It’s common to see a dozen large spiky caterpillars in one place because the butterflies lay their eggs in a bunch, and they all hatch together.

Is This Caterpillar Poisonous?

Yes, it is a poisonous bug. The Spiny Elm caterpillar (as it is otherwise known) is a stinging caterpillar that has urticating spines on its body. 

Some of these hairs or spines can get attached to your skin when you touch this caterpillar. 

These spines release a small amount of toxin inside your body, which can cause irritation, redness, swelling, and in some cases, an allergic reaction. 

If you have weak immunity or are sick, the reaction might be severe and may need immediate medical attention. 

So, mourning cloak caterpillars are poisonous, and you must avoid touching their venomous spines as much as possible.

Is It Dangerous To Humans?

Yes, the spiny caterpillar can sting humans, which can be a bit dangerous if the person is allergic to insect stings. 

We are listing below some of the symptoms which you may face after exposure to the venomous spines of the mourning cloak caterpillar:

  • Redness in skin
  • Itching
  • Skin irritation
  • Blisters
  • Welts
  • Headache
  • Nausea 
  • Vomiting
  • Shortness of breath
  • Allergy
  • Difficulty in eating
  • Pain
  • Burning

If you touch the eyes or nose after touching this stinging caterpillar, then symptoms like coughing, nose bleed, sneezing, and mouth pain can also happen.

You need to remove the hairs immediately from your body after touching the caterpillar’s venomous spines. Use a small tweezer to extract the spine and throw it away afterward.

The symptoms may continue for a few minutes or up to a few days. If it continues for more than one day, you need to visit your doctor.

Does It Bite?

The mourning cloak caterpillars may be poisonous, but they don’t have powerful biting mouthparts. So they will not bite you. 

These caterpillars have mandibles that they use to eat leaves and plant parts, but these mandibles cannot cause much of a dent in human skin.

Is Mourning Cloak Caterpillar Poisonous

How To Treat The Symptoms of Exposure to Urticating Spines?

If a person has a mild reaction after touching the venomous caterpillar’s hair, the treatment can be done at home.

You need to follow the below steps for doing home treatment at home.

  • Remove the tiny hairs of the mount cloak caterpillar immediately. You can do this by using tape.
  • You can place a tape strip on the area of your body that is exposed to caterpillar hairs.
  • Pull the tape to remove all the hair.
  • Wash the area gently with soap and water.
  • If that area still itches, then you can put a paste of baking soda and water over it. But if it will not work, then apply hydrocortisone cream over the area.
  • If you have blisters in that area, then contact your doctor immediately.

What Other Damage Does It Do?

Newly born mourning cloak caterpillars eat the leaves of trees like willows, cottonwood, and elms. They even feed on flowers like knapweed and scabiosa, which can cause significant damage to your yard.

The adult mourning cloak drinks the nectar of plants like red maple and milkweed. They even eat decaying fruits in your garden and consume tree sap.

Some signs of mourning cloak caterpillar damage are rolling leaves, holes on leaves, eggs, and excreta. They might even bore into the wood, which can cause a lot of damage to the tree.

Is Mourning Cloak Caterpillar Poisonous

Other Poisonous Caterpillars

#1. Giant Silk Worm Caterpillar

There are various species of giant silkworm caterpillars, but two species, the Buck moth and Io moth, have poisonous spines.

Buck moth Caterpillar

The buck moth caterpillar is brown to purple-black with various yellow spots. The entire body of this caterpillar is covered with black-colored spines. 

You will commonly find them in oak or willow trees and mainly from spring to summer season in a year.

Io Moth Caterpillar

The Io moth caterpillar is usually light green or yellow. You will find a red line on both sides of these species. These caterpillars eat plants like corn, oak, apple, and roses.

#2. Flannel Moth Caterpillar

There are various Flannel moth caterpillars, but the most common ones with stinging hairs are the puss moth caterpillar and black wave flannel moth caterpillar.

Puss Moth Caterpillar

A Puss caterpillar is a one-inch caterpillar covered with long soft brown hair throughout the body. But 

venomous spines are found just below these long hairs, which can cause irritation and blisters on your body at a slight touch.

Black Wave Flannel Moth Caterpillar

The sting of the black wave flannel moth caterpillar is not as dangerous as a puss caterpillar. 

These caterpillars usually feed on hardwood plants, which you commonly see in the summer.

Frequently Asked Questions

#1. Are mourning cloaks rare?

Mourning cloaks are not rare. They are found in many places across Asia, North America, and Europe. They are rare in Britain, where they are also known as Camberwell beauty.
The behavior of these beautiful butterflies is quite interesting. When the weather gets cold, they hide in rocks and holes in trees, overwintering as adults. 
But during the summer months, they come out and fly again in search of food.

#2. Are mourning cloaks endangered?

No, it is not an endangered species.
Mourning cloaks are quite common in the United States. But it is rarely seen in some parts of the World like Britain and the Gulf states. 
These butterflies are quite beautiful. They feed on the nectar of the flowers of their host plants, including wild roses, black willow, and others.

#3. How long does a mourning cloak butterfly?

They live for almost ten months, more than other butterfly species. It is a large, distinctive butterfly with wings extending up to 3 to 3.5 inches. 
When they close their wings, their body looks like they are wearing mourning cloak, which is the reason behind their name.

#4. Why are they called mourning cloaks?

The mourning cloak butterfly’s colors resemble that of a traditional cloak or loose garment worn by people who have lost their loved ones. 

Wrap Up

Mourning cloak butterflies are a sight to behold in the summer and spring seasons. However, those looking to breed them should be aware that the caterpillars have stinging hair.

We have discussed the steps to follow if these caterpillars’ hairs come in contact with your skin. However, the best policy is to wear gloves when handling them.

We thank you for reading this article!

Reader Emails

Over the years, we have been fortunate to receive many emails from our readers detailing the mourning cloak caterpillars.

Go through the treasure trove of pictures and information in the letters below.

Letter 1 – Mourning Cloak Caterpillar

 

Black Spikey Caterpillar
Dear What’s That Bug,
My son and I found this black spikey caterpillar in the backyard eating some cottonwood leaves. It is mostly black with a lot of tiny white dots, tiny white hairs, and long black spikes all over its body. It also has five pairs of orange feet and rust colored spots down the middle of its back. We think it looks similar to a mourning cloak caterpillar that we saw on your site. Is that what it is? Thank you
Damon

Hi Damon,
You are correct in your identification of this Mourning Cloak Caterpillar.
.

Letter 2 – Mourning Cloak Caterpillar

 

hi bugman.. I came home to find the wall outside my backdoor in Southern Cal. covered with these beasties. They all seemed to be climbing up to my roof and appeared more rarely around other outside walls.
Do I need to call the exterminator? Or should I make peace with them? My dog hasn’t noticed them yet.
Regards
Andy Factor
Los Angeles, Ca.

Hi Andy,
This is a Mourning Cloak Caterpillar which will become a lovely brown butterfly with cream colored wing edges and blue spots. The caterpillars feed on elm, willow, poplar and occasionally the floss silk tree.

Letter 3 – Mourning Cloak Caterpillar

 

I know you are busy, take a look if you can
Hi guys, attached is a photo of a caterpillar I’m trying to ID. I posted it on bug guide too. I also am sending over some other photos I took and posted on bug guide and you can use them onb your site too if you want to. Today I learned on your site the things I was calling silverfish were actually house centipedes and they eat other bugs in the house. Cool. I also read they can produce a painful bite. Not cool. Generally speaking, I’m not a bug killer (we have a “backyard safari” bug vacuum) and all tresspassers are released. Since I’m a high school teacher I always make it a point to set an example when we have a bug intruder in our classroom and make sure it is tossed out the window. Is there a way to post pics to the site like bug guide or do people just mail them to you?

Dear Unknown Teacher,
Since we are control freaks about the aesthetics of our site, we do not allow visitors to post. Imagine what we might find? We do not want Jenna to appear on our homepage one day. This is a Mourning Cloak Caterpillar.

Letter 4 – Mourning Cloak Butterfly Caterpillar

 

These little guys…
Found these little guys climbing out of my Chinese elm tree, here in Southern California. I watched for over an hour as at least 15 climbed down, one by one. Can you tell me what kind they are, and what they feed on? Thanks.
Michelle

Hi Michelle,
This is a Mourning Cloak Butterfly Caterpillar. They were feeding on the leaves of your Chinese Elm and they left the tree to find a good place to pupate. Mourning Cloaks are lovely purplish black butterflies with cream colored wing edges and blue spots.

Wow! Thanks so much for taking the time to answer my e-mail. Our entire evening had been centered around these caterpillars. My children and I carefully collected them as they came out of the tree thinking we would watch then release them as butterflies. Since I wasn’t sure what they fed on and didn’t want them to starve, I placed them back at the base of the tree. I tried looking online several times to identify, but had no luck. I even woke in the middle of the night thinking of them….funny. Anyway, it was SO NICE to find your e-mail with the answer, and the kids (2 & 4) were amazed with the pictures and facts I was able to then find on the internet. Thank you for helping keep our interest “peaked”. All that right in our own back yard! So cool. Take care.

Letter 5 – Mourning Cloak Caterpillar

 

SoCal Caterpillar, Agraulis vanillae?
Location: La Crescenta/Montrose California
March 14, 2012 3:45 pm
Hi Bugman! I came across a caterpillar today and tried figuring out what it was. Due to just moving here from Florida, I’m sure my area has tons of new bugs (including the giant black widow I found a while back!!) It looked like an Agraulis vanillae BUT it’s a bit different. It’s black/gray with 2 tight red/orange striped along its back. The spikes are NOT clumps of hairs, but actual single spikes.
I took 2 photos. 1 is on the concrete of my porch where I found it. The other is where I put it; a white rose tree.
Please forgive my photos. All I had near me was my phone, but I think the photos are good enough.
Signature: Thank you!

Mourning Cloak Caterpillar

Though your caterpillar resembles that of the Gulf Fritillary, Agraulis vanillae, it is actually that of a Mourning Cloak, a lovely large purplish, black butterfly with creamy wing edges and blue spots.  Mourning Cloak Caterpillars feed on native willows but they are very content to feed upon the leaves of cultivated Chinese elm as well.

Letter 6 – Mourning Cloak Caterpillar

 

Mourning Cloak?
Location: Denison, Texas
April 5, 2012 6:08 pm
I have seen about 13 of this in one afternoon crawling around. Is this a mourning cloak? Can they hurt you?
Signature: Thanks

Mourning Cloak Caterpillar

You are correct.  This is a Mourning Cloak Caterpillar.  They can often be present in great numbers as you have witnessed.  According to the Auburn University webpage on Stinging Caterpillars:  “Several species of nymphalid larvae bear conspicuous bristled or multi-branched spines similar to those found on some stinging caterpillars. One species, the spiny elm caterpillar (larva of the mourning cloak butterfly), is reported to possess urticating spines.”  According to BugGuide:  “Caution: Do not touch the larva; its spines may cause a stinging sensation if handled.”

Letter 7 – Mourning Cloak Caterpillars

 

Subject: Centipede? In SoCal
Location: southern california
March 23, 2016 5:58 pm
Hi! my wife and I just got a new puppy, and as we were taking him out to the restroom he saw the attached bugs in our tree. we have noticed them dead on our front porch and crawling on our fence as well. Theres ~100 in the tree. We just need it identified to see if its poisonous and how to rid them of our yard so our pup doesn’t have the opportunity to eat them! Its spring, in southern california, been hot the past week.
Signature: kg

Mourning Cloak Caterpillar
Mourning Cloak Caterpillar

Dear kg,
While we do have Centipedes in southern California, your images depict Mourning Cloak Caterpillars, and though they may deliver a slight sting if carelessly handled, they are harmless.  There is no need to eradicate them from your tree.  They may climb to the eaves of your home in groups to form chrysalides.  Mourning Cloak Caterpillars will eventually metamorphose into lovely adult Mourning Cloak butterflies.  Some years, when conditions are favorable, the Mourning Cloak Caterpillars can be quite numerous.  Their local native host is willow, but they have adapted to feeding on the leaves of Chinese elm in California.

Mourning Cloak Caterpillars
Mourning Cloak Caterpillars

Letter 8 – Mourning Cloak Caterpillar

 

Subject: catepillar, bug, and spider
Location: Shore of Hells Canyon Reservoir, Oregon side
May 18, 2016 8:32 am
My son took these photos of some interesting invertebrates in our campsite. The vegetation is blackberry, rose, and common hackberry for trees.
We would love to know what species these are or any information you could give us.
Signature: Barbara Webb

Mourning Cloak Caterpillar
Mourning Cloak Caterpillar

Dear Barbara,
This is a wonderful image of a Mourning Cloak Caterpillar, and we will be posting it to our site to help our readership identify them in future encounters.  Your other insects are an immature Katydid and an Orbweaver spider.

Letter 9 – Mourning Cloak Caterpillar

 

Subject: ? Butterfly Larva
Location: southeast Michigan in June
June 17, 2017 6:06 pm
I am a hopeless butterfly enthusiast who came across this interesting caterpillar crawling along the
paved trail in our state park. I am familiar with the common butterflies found in our area, but my
research provided no matches for this larva. It was clearly in the wandering stage, seeking out a place to pupate. I hope you will be able to solve my little mystery. I would love to know to which
species it belongs! Many thanks in advance.
Signature: Kathy Genaw

Our Automated Reply:  Thank you for submitting your identification request. Please understand that we have a very small staff that does this as a labor of love. We cannot answer all submissions (not by a long shot). But we’ll do the best we can!

In the interest of not wasting your valuable time, I want to let you know that I
was able to identify my butterfly larva.  It is a Mourning Cloak caterpillar!
Thank you for the great work you do!
Kathy Genaw

Mourning Cloak Caterpillar

Dear Kathy,
We are thrilled to post your image of a Mourning Cloak Caterpillar.  Theyy do wander in search of a suitable site to undergo metamorphosis, and we have several images in our archive of Mourning Cloak chrysalides under the eaves of homes.

48 thoughts on “Is Mourning Cloak Caterpillar Poisonous?”

  1. My neighbor and friend of my sons came by today with a new friend! We looked it up and it was a Mourning Cloak Moth Caterpillar!He and my boy were excited to see what it was going to change into and what it will eat.You guys were dead on with munchies for him,he went straight to it!Lol Thank you for this great informational site!Keep up the amazing job,I use this to teach in my neighborhood and to create a sense of wonder with Nature with the Kids! Living in Eau Claire Wisconsin we have found alot of “global warming” bugs and this helps to figure out the weirder ones.I will recommend this to EVERY parent for those harder to ask bug questions—Zach Rediess

    Reply
  2. I find it so weird that these are poisonous caterpillars because when I was about 12 I caught 5 of them, played with them and touched them a lot. Nothing to my memory ever happened to me.

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  3. I live in Henderson NV and I spotted this unusual caterpillar on my sidewalk. I had never seen a black caterpillar with red dots on his back. . my friends keep saying that it was not a caterpillar. they said it may be a cendipede and I begged to differ. it wasn’t moving until I put water on it.
    what’s going to happen to it now? do I just leave it alone?

    my email address is [email protected]

    Reply
  4. There are several “families” of them in a tree in my front yard — yes, hundreds of them! 🙂
    – Southern California

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  5. There are several “families” of them in a tree in my front yard — yes, hundreds of them! 🙂
    – Southern California

    Reply
    • Some have begun leaving the tree. I missed the mass migration on Monday, the 30th, but yesterday I saw some going off to find a place to make their chrysalises. They move quickly! But there were blue birds around and several (fat) lizards. There are 2 chrysalises I see hanging under the eaves of my house with about 6 more caterpillars looking like they might have found a place to hang in their “J”. Hopefully, in a few weeks I will see some butterflies!

      Reply
  6. We have a willow tree in the front our home and recently found 100 caterpillars on our home. Later in the week we found at least 20 nests in the tree with hundreds of baby black worms. I am so close to calling an exterminator because I’m so concerned about all of them crawling on my house. I’m quite anxious about all this. Please afvise

    Reply
    • Mourning Cloak Caterpillars may use your eaves to metamorphose into the Chrysalis stage, but they will not harm your home.

      Reply
  7. Just found a bunch on my hammock under my big Chinese Elm in my backyard and on the ground. Does anyone know how long they hang around? I don’t want my dog eating them and/or either of us stepping on them. Thanks!

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  8. I just saved at least 50 from ravenous birds!! Already in pray position! They do well with egg crates and a giant cookie jar with Chinese tree leaves! They marched from one end of my yard to the other ” wondering” with purpose! They ate my tree!!

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  9. We have been doing the Bugs In Our Schoolyard program at our Boys & Girls Club (JAMS Clubhouse) in Santa Monica. We found 2 of these caterpillars marching across our patio. We were so amazed to see them! Very cool.

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  10. Today after 15 days of careful watch every mourning cloak butterfly emerged from there amazing transformation ! I fed them some rotted watermelon , they basked in the warm sun for a couple hours. We said our goodbyes! They seemed to float happily with every gust of wind . One by one . Then there were none . These little guys for the record do not eat your garden flowers! Amazing !

    Reply
    • Thanks for providing your wonderful experience with Mourning Cloak butterflies. You can continue to put rotting fruit in your garden to provide them with food.

      Reply
    • Mourning Cloak Caterpillars are not deadly poisonous, though if you had that concern, you should have sought medical advice rather than an internet web site. Local irritation may occur as the site of a sting.

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  11. Today (Saturday) I noticed about 20 of these guys under the eaves of my house. Some are hanging in a J and some are still laying flat. A few were still crawling up the wall toward the others, presumably to find their spot. Super cool. The only problem is that on Monday morning there will be painters coming to power wash my house and repaint! I’ll have to move them tomorrow (Sunday). I’ve just read about how to move them as chrysalis but can I move them as a J? Will I totally mess up their process?

    Reply
  12. Just went outside to find about 30 of these guys all over the backyard, our Chinese Elon and the outside and waves of our house. They are huge, and very fast! I have two toddlers and a German shepherd who all love playing in the yard I told them to not touch the caterpillars but these guys are everywhere – are they dangerous if the kids were to accidentally touch one? There are also a group of sparrows going wild in the neighbors yard and I’m assuming they found their caterpillar family -I want to protect the ones in our yard is there anything I can do?

    Reply
    • We have read that Mourning Cloak Caterpillars might sting, but to the best of our knowledge, the sting is not dangerous. The caterpillars do have spines which makes it difficult for many predators to eat them

      Reply
    • I played with these in the Bay Area in ca in the front yard in early spring we had so many of them I kept them until they transformed into butterflies and played with them daily after school and so did my friends I never had any issues with them and they were a huge part of my childhood every year!

      Reply
    • According to BugGuide: “Caution: Do not touch the larva; its spines may cause a stinging sensation if handled. The pupa of the Mourning Cloak is harmless – unlike the pupa of tent caterpillars (Malacosoma species), which may cause an allergic reaction on the skin if handled by allergy sufferers or individuals with very sensitive skin.”

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  13. I have a couple of these on my courtyard, but non of them have opened. They’ve been hanging for more then two weeks, how long does it take for them to transform? Also, I live in southern California and it’s been hot.

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  14. We have two mourning cloak caterpillars that seem ready to pupate but they are not hanging upside down yet. They have been holding on horizontally to under-side of a stick for several days without moving. They are still alive, but I’m wondering if this is normal.

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  15. I found this while working at a house yesterday in Lacrosse, WI. He got dragged into the towel I was using and felt his spines as I was working. He seemed fairly chill. We like to name unusual bugs we find, so this guy is now ‘Goliath’.

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  16. Years ago in the 1970s my parents Chinese elm tree hedge became full of these caterpillars. My mother thought they were harmful grubs. She found a way to kill them. She would take branches full of them and burn them in a garbage can. Years later I became very interested in butterflies and caterpillars. I even learned to raise monarchs and painted ladies. I’ve learned they were caterpillars that turned into mourning cloaks. My mother didn’t kmow.

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  17. We seem to have several around our home and many are hanging in the chrysalis stage right now. Southern California.

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  18. I just caught morning clock caterpillar I was playing with it for quite a while and then I got some poking me and I was curious why esteemed we thought it was a poisonous but it was figured out that because of my aunt and the website thank you this is very helpful now I know for next time

    Reply
  19. We just found hundreds of these caterpillars in our community on a tree. Many of them have died but we saved a couple of dozens by taking them home. They are ready to hang upside down and pupate. So cool! I am very much tempted to handle them but they are scary looking 🙂 my kids and I can’t wait to see the butterflies.

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  20. i found one of these hanging from a concrete wall out by Fountain Valley, California. I wanted to bring it home so my son could see it transform but was afraid if i moved it it would mess up its process. very curious caterpillar.

    Reply

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