What Is This Orange and Black and White Spiky Caterpillar On the Milkweed?

Most Canadian children grow up being read stories about Monarch butterfly caterpillars feeding on Milkweed leaves. They may be surprised when they see a totally different caterpillar chewing steadily away on a Common Milkweed leaf. These other ones are very spiky looking with black and white tufts and a strange colour combination of orange, black and white. They aren’t butterfly caterpillars, though, they are moth caterpillars.

Photo of Milkweed Tussock Moth Caterpillar General on NaturalCrooksDotCom
A Milkweed Tussock Moth caterpillar hanging out.

We used to see these caterpillars fairly often when I was growing up but I haven’t noticed them in recent years. Then, while on a guided nature walk at the Riverwood Conservancy in August, one of the participants pointed out two of them eating away at a Common Milkweed plant in the Maintenance Loop.

Be Careful! Don’t Pick Up a Tussock Moth Caterpillar!

Just a word of caution: Many Tussock Moth caterpillars have spines that can cause mild to severe skin irritation if people handle them. It’s best to just observe them from a distance and not risk injury.

What Made These Holes in a Milkweed Leaf?

Photo of Milkweed Leaf Damaged by Milkweed Tussock Moth Caterpillars on NaturalCrooksDotCom

You can see the type of damage this almost mature caterpillar has made to this leaf.

According to Bugguide, when they are tiny, Milkweed Tussock Moth caterpillars often feed together on the same plant but they usually move away to their own plants as they get near maturity.

Photo of Milkweed Tussock Moth Caterpillar Vertical Hang Milkweed on NaturalCrooksDotCom

Different insects, and insects at different sizes in their life cycles, often make different types of holes in milkweed. Baby monarch caterpillars, for example, usually eat from the underside and often don’t get all the way up through the leaf. Milkweed Beetles often chew pieces out of the edges of leaves.

Hey, Someone Pooped On This Leaf!

Photo of Milkweed Tussock Moth Caterpillar Frass on NaturalCrooksDotCom

One way to spot caterpillars, which often hide underneath leaves while munching, is to look for the “frass.” This pile was deposited by one of these Milkweed Tussock Moth caterpillars while it ate.

Are Milkweed Tussock Moths Large and Showy Like Monarch Butterflies?

Unfortunately, I don’t have a photo of one of these moths. You can see some nice ones online, though, on the Bugguide webpage. The body has some interesting orange, black and white markings but overall the moth is quite plain.

The wingspan, according to Bugguide, is 32-43 mm (or about 1-2 inches.)

Photo of Milkweed Tussock Moth Caterpillar Red Feet on NaturalCrooksDotCom
Notice the little reddish “feet” add extra colour.

I’ll keep an eye out for the moths now I know that they are around but I’m skeptical whether I will find any. In the meantime, I enjoyed a chance to see an old friend from my childhood.

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Have you seen any of these brightly coloured caterpillars in your neighbourhood? Please share your sighting with a comment.

8 thoughts on “What Is This Orange and Black and White Spiky Caterpillar On the Milkweed?

  1. Unfortunately we found these little boogers eating our Asclepias plant. (orange butterfly flower) Just 7 of them took almost all of the orange blooms from the bush over night! We had never seen them before, but got this new perennial this year. Thank you for the pictures. None of our neighbors had seen this caterpillar before either.

    • While I’m sure it’s upsetting to see the flowers munched, these moths are just as important in their own way as the Monarchs, even though they are not talked about as much. So you’ve been helping a native species that also has had problems due to loss of habitat. I’m not sure if Butterfly Milkweed will sprout new flowers but it likely will as Common Milkweed does. Hope so!

  2. Thanks for the photo. I just identified one on my milkweed here in Southern Pennsylvania, USA thanks to your website. She/he is very happily munching away.

  3. We have a lot of milkweed around here, close to Belleville, Ontario and we have a lot of these caterpillars. I was wondering if they might be edging out monarch caterpillars. The last couple of years, I can’t find any monarch caterpillars. I still see some butterflies occasionally just not the caterpillars.
    I’m glad these are good for plant life but the monarchs are prettier. 😉

    • Yes, Monarchs are real beauties! I doubt that the Tussock Moths are out-competing the Monarchs as they don’t directly have any way to attack each other. I’d be more suspicious of ants which are known to eat Monarch eggs and some other similar predators. If I understand correctly, the Tussock Moths lay quite a few eggs in one spot so the odds are good that not all will get eaten before they hatch. Monarchs usually dot their eggs only one or two at a time so they have no “safety in numbers.” I hope you get more Monarchs next year, though!

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