Attack of the mourning cloak butterfly larvae

That title sounds contradictory, doesn’t it? Butterflies are beautiful, innocuous, always to be protected. If only the world were as Walt Disney told us it was! [NOTE: I’ve learned from readers of this post that this caterpillar has a toxic substance in its hairs or spines that can cause a very painful reaction if you touch it, so be careful—indeed of any hairy or spiny caterpillar. See below,  and ]

The first title of this post was “Attack of the tent caterpillars”, because of what I saw. First the caterpillars,


then their “tent”. The black balls visible are probably frass (caterpillar excrement). A few caterpillars are under the tent; some species retire periodically to their tent for protection from the elements and birds.


The closer I looked the uglier they were to me.


They were chowing down on the leaves of our little grove of aspens, planted a few years ago and much cherished.


Birds, including 6 pairs of nesting tree swallows (Tachycineta bicolor), usually keep insect pests under control around our house. But nobody showed any interest in this concentration of food on the aspens; too spiky, or maybe bad-tasting. Caterpillars eat so much so fast, they can defoliate trees. I went looking for something to spray them with and found we had no insect spray. Finally I used 409 cleaning spray, it certainly smells toxic. The next day most of the caterpillars were still alive and eating. Finally a better idea occurred: cut off the branches they were on and bag them up. Since the infestation had spread to just 3 branches, I was able to do that.

It was only afterwards that I succeeded in identifying the caterpillars. I had looked at all the so-called “tent caterpillars”, and others, without finding anything that matched. Then there they were: they would have grown up to be mourning cloak butterflies (Nymphalis antiopa).


Photo from milesizz on flickr.

You can imagine how bad I felt. I’ve since thought that maybe I could have cut the branches and then lodged them in among the branches of some other tree. Or kept some and fed them until they pupated. The favored food trees for the larvae are elm, willow, hackberry, and trees of the genus Populus: cottonwood, poplar, birch, and, yes, aspen. Except for occasional cottonwoods and shrubby willow along the river, none of these are native around here. But we do see the occasional mourning cloak, one of which must have laid the eggs earlier this spring—this species overwinters as adults, emerges to mate and lay eggs in spring, then after 10 days or so the caterpillars hatch out, eat, pupate and emerge as butterflies before fall. Given how much caterpillars eat, harvesting enough willow from the riverbanks to keep them fed doesn’t sound practical, at least not for very many individuals. But if there is a next time I think I will try it.

Here are a few closeups of the caterpillars. Identification was hard, maybe because they go through 5 “instars” or stages, shedding their skins each time and so perhaps different instars look a bit different. Some of the photos of this species showed much hairier-looking caterpillars, whereas the ones here were extremely spiny but with few hairs.



Note the red dots on the back, and the red legs (arrows).


The eggs would have looked like this.


Photo from Canadian Biodiversity Information Facility. For an excellent series of photos showing a female laying eggs, changes in the eggs as they get close to hatching, and the tiny new caterpillars, see this page by Bea Laporte.

And each spiky black voracious caterpillar, after eating its fill of the tender leaves of our aspens, would have toddled off to some sheltered place to pupate, making a chrysalis like this.

Mourning Cloak Chrysalis2.jpg

Photo from

Since mourning cloak adults overwinter, they are one of the earliest butterflies to appear, and regarded as a sign of spring. The “mourning cloak” refers to their dominant wing color, dark rusty red bordered with black—though it’s lightened with blue jewels and cream-colored edges.


I’ll close this tale of butterflies-never-to-be, with a melancholy ballad in which the mourning cloak appears, perhaps in the role of one of the Greek Furies, haunting one who has done wrong. Usually such messengers of vengeance and doom have unpleasant appearances, as did the Furies, but to the guilty heart a bright butterfly might be even more menacing than a dark spiky caterpillar.

The Mourning Cloak
(Karah Stokes/Spruce and Maple Music 1)

One fair morning late in June
The sun shone on the daisies white
When a messenger of sorrow deep
Came into my garden bright

Wings of deepest velvet black
Bound with gold and sapphires rare
A butterfly, a Mourning Cloak,
Like one a wealthy widow’d wear

He promised me a golden ring
But he gave it to a rich man’s child
He craved the ease wealth would bring
Above a love both true and wild

So I called him to our trysting place
“Since there’s no help, let’s kiss and part”
He took me in a sweet embrace
And he felt a penknife in his heart

He looked at me with fading eyes
I left him there as he left me
The dawn next morning brought the news
That he’d been set upon by thieves

Oh, butterfly, why do you haunt?
Know you the secret in my breast?
I pierced his heart as he pierced mine
I slew the one I loved the best

One fair morning late in June
The sun shone on the daisies white
When a messenger of sorrow deep
Came into my garden bright


28 thoughts on “Attack of the mourning cloak butterfly larvae

  1. Ugh.. I wish I would have discovered this blog earlier. Please keep my email!! If you should find more, I would purchase them from you and pay for Overnight FED EX.
    I found you by accident when I went looking for larvae for these creatures to use for a funeral mass ‘release’.

    • This is a bad idea in so many ways! To release mourning cloak butterflies at a funeral is to use living creatures just for a dramatic emotional effect. Unless the funeral is held in a an area full of the right kid of flowers, the butterflies can’t feed, and unless there are the right kind of trees, they can’t lay their eggs on places where the caterpillars will be able to eat.

      Then there are the practical considerations. As for shipping you the caterpillars: they may not survive the trip; if they do you must be prepared to feed them particular foliage until they pupate, and then wait while they metamorphose into butterflies. How can you possibly time that to coincide with a certain date? If the butterflies appear too early, you must feed and house them until the funeral.

      I am really hoping that you were making some sort of joke. Let’s just admire butterflies when we are fortunate enough to see them, and not try to use them as if they were living confetti.

  2. Um.. actually, NO, no joke and there is plenty of foliage/flowering plants around the area for the caterpillar/ butterfly to eat – I live in MA and we have this species of butterfly here already – certainly a better way of ‘disposing of them from your tree’ then hauling them off in trash bags and killing them (as you did).
    As for the ‘showy confetti’.. you are very arrogant! I am Buddhist – this was PRIVATE thing that I wanted to do with my children to celebrate the LIFE in death – I am sorry that I ever found your blog, you are rude and showy and apparently enjoy belittling people.

  3. Kat,

    I apologize. None of the information you mention was included in your original comment. And keeping voracious caterpillars alive for a couple of months, gathering the right leaves for them to eat, while they grow and shed their skins 4 times, then ten days or so before the butterfly emerges…not easy to do and pretty hard to match up with any scheduled event.

    I hope you can see why I jumped to the wrong conclusion.

  4. I just found this post after googling myself. (Not from vanity — I’m reading a New York Times article telling how to suppress online information about yourself). DON’T SUPPRESS THIS! I love it, and I’m glad you credited me with writing the song. I wrote it after a mourning cloak flew into my yard on a brilliant summer day and I was thunderstruck with its beauty. I had hoped to see one for years but had lived too far south to do that until that day. It was the most gorgeous thing I’d ever seen. I marveled, too, at the sadness of the people who saw such a beautiful creature and gave it such a sad if descriptive name. (They’re found all over the world in northern latitudes, but in Britain, they’re called “Camberwell Beauties.”)
    Louise Erdrich has a section in The Blue Jay’s Dance that talks about finding them as pupae, carefully scraping them with a silver spoon from the wall of her writing shed, and pinning them on a sheltered wall so carefully that they hatched successfully. That’s one more reason Louise Erdrich rules!
    I probably would have thought they were caterpillars and done just what you did.

    • Karah,
      Funny — I was googling your song after listening to Laurie Lewis’ recording. It’s hauntingly beautiful and I hope to sing it at a party next week. But I love butterflies as well, so a big success on all fronts. I was very pleased to see this blog post (excellent, btw, with superb photos), with your lyrics and see you found it as well — seven years earlier.
      Louise Erdrich!

  5. I enjoyed reading your post and was very glad at the happy ending! It’s wonderful when we have a chance to see these creatures up close, as well as to rescue one from two different predicaments as you did. (You’re welcome to the photo, thanks for linking back.)

  6. “Are mourning cloak larvae caterpillars poisonous? ”
    Interesting question, to which I did not know the answer. It turns out that they are, in a way: they have “urticating spines”, visible as stiff hair-like structures, that are hollow and connected to glands which produce an irritating toxin.

    This is, of course, a defensive tactic, meant to protect against predators who might gobble up tasty caterpillars.

    I wasn’t able to find anything specific, in my short search, about exactly how irritating it is to humans. The best write-up (from Auburn University, at described the effects of so-called “stinging caterpillars” of all species this way: “Reactions to contact vary and include: slight to intense nettling, stinging, itching, or burning sensations; development of dermatitis, rash, lesions, or pustules; inflammation, swelling, and numbness at or around the area of contact; fever and nausea; and, in some cases, intense pain. The type of reaction depends on the species of caterpillar, degree of contact, type of toxin, and susceptibility of the individual. Reactions may be especially severe for individuals with allergies or sensitive skin.”

    Definitely something to avoid touching with the bare skin! Since these caterpillars hang out in groups one might easily brush against several at the same time, increasing the exposure. Pets could also suffer if they nosed around or brushed against these creatures. Contact with spines of dead caterpillars can still cause this irritation, since it is not something that the caterpillar willfully does.

    A final bit of information which turned up is that Mourning Cloak butterfly caterpillars are called “Spiny elm caterpilllars”.

    And there’s a page about various species of stinging caterpillars with very good photos and some information, at

    Thanks for the question.

  7. I was recently stung by one on these little guys. He found his way into my home and onto the arm rest of my black sofa. Lol..I have never jumped so high so fast! My arm hurt from shoulder to fingertips for the entire day without relief from any treatment. Needless to say I don’t want them exterminated since I see that they are beautiful butterflies…but should one of my children get stung I will be quickly disposed of.

    • Wow, that’s a terrible reaction. And you had no idea that the caterpillar was even there. Fortunately it seems a pretty rare occurrence for caterpillars to be found indoors, unless accidentally brought in with some flowers or foliage. I’m resolving to be extra careful around any hairy or spiny caterpillars I see in future!

  8. This morning I went outside to find about 6 of these spiny black caterpillars in my yard plus a couple of dead ones. Is it safe to assume that maybe the eggs were laid in my Chinese elm tree and that they are coming from there? When I researched and saw the beautiful butterfly they become I want to ensure that my little friends are kept safe. They are wandering on my patio furniture and bricks. Should I put them back in the tree?

  9. Okay so now we find about 6+ every morning wandering around on the patio furniture covers. There is also a tremendous amount of excretment as well. The caterpillars are at least 2 inches long. How much longer till they cocoon themselves so we can get back to using our patio furniture without risking one falling on our head? I’m trying to be gracious, but my kids are itching to use the fire pit.

  10. Theresa,

    I’m not an entomologist, but I will pass on the best information I have been able to find.

    Good news: if they are mourning cloak butterfly caterpillars, they stay together until ready to pupate, which takes about 4 weeks. Then they show ‘wandering’ behavior as each one seeks out a good place to form a chrysalis & turn into a butterfly. And I found one reference that says the caterpillars measure about 2 inches in length when they are mature, so that is encouraging too for your future outdoor activities. (By maturity they have shed their skin 4 times as they grow.)

    You might watch where the ones out of the tree go, maybe you can kindle the scientific spirit in your kids and assign each to watch one caterpillar. They are said to go 10-50 meters looking for the right spot to climb up (a tree, or to the windowsill, eaves or clapboards of a house), attach themselves with silk, and turn into a chrysalis. That part would be neat to see (and photograph): one description says,

    “Next the caterpillar arched its body upward entangling the hooked claws of its hind legs in the silk, letting its body hang downward with the head end curved slightly upward. Several hours later the skin along its back began to split just behind its head. Gradually the thin spiny skin worked upward as the caterpillar wriggled. Finally the little shriveled mass of skin either fell to the ground or stuck to some of the webbing and remained there.

    “Now this peculiar looking grayish-brown object, the chrysalis, hung as quietly and inert as a mummy. Several of those I touched wriggled vigorously, then resumed their quite helpless position.”

    If anybody has the urge to watch a butterfly emerge, here are some instructions for keeping the chrysalis:

    It’s really important that the container be large; if the butterfly is cramped when it emerges the wings will not unfold and develop properly.

    It’s too bad that (as far as I know) no technological breakthrough has enabled us to see and record what goes on inside the chrysalis. The transformation of caterpillar to butterfly involves the dissolving of nearly all the body of the caterpillar by enzymes, and then it is re-generated by little groups of cells that developed partway in the caterpillar and then stalled, waiting for the right time to create the parts of this new creature. Some more details here,

    It is really good of you and your family to endure the caterpillars good-naturedly as you are, and I hope that they are ready to move on to the next stage of their lives and let you enjoy your patio.

    By the way, one more bit of information is that the droppings of insect larvae like caterpillars is called frass, which maybe your kids will find more exotic than calling it falling poop or caterpillar poo.

    Let me know how it turns out, would you please?

  11. Thank you so much for your reply. It was very helpful! I know that there is no real replacement for Mother Nature but as I found more & more of these dead on my patio (squished, drowned or partial bird/ant food) I began gathering them in a plastic tub with plenty of elm branches till I could figure out what to do. I was able to borrow a butterfly enclosure from my school to keep them safe. I would have gladly left them alone to wander my backyard but as they grew larger my dog became more interested in them. Since they are a stinging caterpillar I was a bit nervous about them coming into the house and or stinging my dog. I am sure that most of them stayed in the tree. These might have been the weaker ones that fell from the branches. I will let you know how things turn out. I am hoping to release some beautiful butterflies in the very near future.

  12. Just want to give you an update on my caterpillar colony. I have 15 chrysalis in one container and another 6 in a smaller one. Outside we have about 4 under the eaves of our house. This has been quite an experience and I can’t wait to see these beautiful butterflies. I hope my elm gets chosen for another generation next spring.

  13. Hi, just wanted to thank you for the information, which I discovered while searching to see what the Mourning Cloak caterpillars look like; I’ve been seeing a lot more of the butterflies in my yard this year than usual, maybe due to our extremely early spring here in the Michigan Upper Peninsula. Ugh — I’m pretty sure that, not knowing what the caterpillars were to turn into, I would have done the same thing and gone for eradication! A couple of years ago a lot of my plants were overrun by Painted Lady cats that are also less than good looking and I sprayed them with BT to kill them, then had to suffer the guilt once I learned what they were… But I have to say, I far prefer the Monarch and Swallowtail larvae, which have always reminded me of the hookah-smoking caterpillar in Alice in Wonderland — LOL ! Oddly, I haven’t actually seen any of the MC larvae, but our aspen (or “popple” as it’s usually known around here) is all pretty tall and just part of the woods around our house, so I suppose they’re up there happily chomping away. Thanks again for the good article — Sandy

  14. i saw two of these flying in back back yard and i capture them and pin them down they are fascinating!i love looking at them daily they make me happy!

  15. Katie/Monday, May 13, 2013
    We have these caterpillars in our backyard and they love our Hackberry tree. We have lived here for 10 years but this is the first year we have seen so many of them. We had 83 Chrysalis in our yard and most have already emerged. They started climbing the walls of our house and garage and hung out under the eves. We did pick up several and not once did I or my son have a stinging from them. They are very cool and such a beautiful butterfly!

  16. Just found 2 of these caterpillars hanging out in my garage in Hamilton, OH!! We have a lot of cottonwood trees which are currently seeding – first time I’ve ever seen these little guys. I put them back amongst the trees – hopefully we’ll get to see some of these beautiful butterflies soon! Thanks for the blog and all the information!

  17. I found a whole lot of them, somewhere between 15 and 20 on a tree-like shrub. I’m sure it’s some sort of sprout of a tree. Actually, my neighbor’s daughter’s boyfriend found them when he ran out of weed-eating twine. He was getting rid of my weeds in my fenced in area of my apartment where we park our cars. I can’t wait to take pictures daily or every other day to see what happens.

  18. Our family looked after ‘Trooper’ who was born with a folded wing for around a week. He’d been blowing around on our cement portal, having lost one wing completely the 2nd time we noticed him. Google informed they like sugary water, flowers, bananas and other fruits and so put him in a deep windowsill and fed him. It seemed he liked having some sugar water on the end of a Geranium stem. On offering him some yesterday, his tongue appeared to be stuck in it, like it was too thick. He didn’t move from his position and died overnight. (we thought he’d died for sure several times- then he ‘came back’ to life to our surprise!) We lifted him onto a paper with his flowers and put him in the trunk of a tree to say goodbye. If you are fortunate enough to experience tending to a butterfly – let them choose their food and don’t try to feed them. The Mourning Cloak butterfly can live up to 12 months and he had just come out of a chrysalis on the portal ceiling. There was nothing for a butterfly on our portal and we thought he’d not make it on our lawn or flowers with the sprinklers and not being able to fly. We now wish we’d have put him in the tree as this species likes tree sap, or known to let him choose his own food, not try to feed him.Trooper was a happy little butterfly even in his tough circumstances. We hope this information helps another butterfly someday.

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