Are Woolly Bear Caterpillars Poisonous? Toxicity Explained

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Woolly caterpillars are cuddly, and lots of people want to keep them as pets. But one question always comes up – are woolly bear caterpillars poisonous, like many others are? Let’s put all the fears at rest once and for all.

Caterpillars often make an appearance in kids’ storybooks as friendly worms. Yes, these insects are usually not aggressive and do not bite humans.

However, they are certainly not always something to be played with. In fact, some of the caterpillars can be so dangerous and poisonous that they can kill humans.

In this article, we will discuss the woolly bear caterpillar and find out if they are poisonous to humans and pets.

Are Woolly Bear Caterpillars Poisonous

What Are Woolly Bear Caterpillars?

Woolly bears are caterpillars that grow up to be tiger moths. These caterpillars have fine and dense hair all over their bodies.

There are around eight or more types of caterpillar species in the United States that have such hair on their bodies and can be called woolly bears.

They are also known as banded woolly bears, fuzzy caterpillars, and more. These insects have black-colored bodies with rusty bands in the middle.

You can spot them in different regions of the U.S., southern Canada, and Mexico.

The chance of an encounter with a woolly bear caterpillar is highest during autumn, which is when they leave the food plants and shift into warmer spots to hibernate throughout the winter.

Are They Poisonous?

Wolly bears are not poisonous, and they are mostly harmless to people. These insects are not even aggressive, and they usually curl up like a ball to play dead when they feel threatened.

They lack a stinger and do not bite. However, if you touch them without any protection, there is a chance that the stinging hairs on their body can break into your skin, causing irritation and pain.

Other Poisonous Caterpillars

While the woolly bears are not poisonous, there are many other venomous caterpillars that can be lethal for humans. Here are a few of them:

Buck Moth

These caterpillars can grow up to 2 inches in length. They have a blackish-purple bodied topped with some bright yellow spots. Buck moth bodies are filled with sharp spikes that are harmful. You are likely most encounter them during the mid-summer season in willow trees.

Io Moth

Io moth caterpillars are green to yellow in color and have a red line bordering their body. They also can grow up to 2 inches in length and have black spikes all over the body. They usually eat plants like roses, corn, elm, oak, apple, clover, and more.

Puss Caterpillar

They show an average growth of an inch. A Puss caterpillar has a wooly coat of brown hair beneath which you will find a bunch of poisonous spikes that can cause problems like severe irritation in humans. You will find them feeding on trees like apples, maple, oak, and more.

Slug caterpillars

Slug caterpillars get their name from the habit of crawling around in leaves like a slug. If you look at them from above, you won’t be able to spot the head and legs. You are most likely to spot them crawling around leaves during the late summer.

Do They Bite or Sting?

Wolly caterpillars don’t have a stinger which is why they don’t bite humans. On top of that, they are not aggressive; if they feel threatened, they will curl up like a ball to play dead.

Banded Woolly Bear

Do They Harm Humans or Pets in any way?

Although these insects don’t bite humans or pets since they are covered with fine hair, touching them without proper precautions can cause problems. The hair is strong enough to break past the human and cause severe irritation. Also, if your pet swallows one of these, the hair can get stuck in the throat, which will cause problems like allergies, gagging, coughing, and more.

Are They Dangerous to Plants?

The woolly bear caterpillars often feed on garden plants, flowers, and shrubbery.

They chew out big holes in these plants, and if a big group of caterpillar attack one plant, they can damage it to quite an extent.

On top of that, when they eat these plants, it decreases the aesthetic value of the garden flowers.

What Do They Turn Into?

The woolly bear caterpillar grows up to become an Isabella moth or a Giant Leopard moth, which is considered the largest tiger moth in the east. You will be surprised to know that it can take around 14 years for the eggs to turn into a complete moth for these species.

Woolly Bear Caterpillar

How Do They Survive Winters?

To survive the cold temperature in winter, the woolly bears search for warm places like rocks, fallen logs, and more to crawl into. They spend the entire winter hibernating in such spots.

There is folklore according to which these insects can be helpful in forecasting the weather.

If the brown band in their bodies is wide, there will be a comfortable and mild winter. However, if it is a completely black caterpillar, the upcoming winter will be harsh.

Frequently Asked Questions

What happens if you touch a wooly bear caterpillar?

Woolly bear bodies are covered with fine spiky hair, which can cause problems for humans.
If you touch them directly, the hairs will break past your skin and cause severe irritation and redness. But fortunately, these caterpillars are not poisonous.

Are wooly worms poisonous to touch?

No, woolly worms are not poisonous to touch, but they can lead to problems like severe irritation and redness in the body.
These insects don’t bite and are non-aggressive. If you want to touch them, it is better to use plastic gloves to stay safe.

What do these caterpillars turn into?

A woolly bear caterpillar turns into a giant leopard moth. These moths are considered the largest tiger moths in the east.
Also, it takes around 14 years for the giant leopard moth egg to fully develop into an adult moth.

What is the most toxic caterpillar?

The giant silkworm moth caterpillar is the most poisonous caterpillar in the entire world. It has bristles in its body that inject deadly venom.
Do not ever go near these insects, as they are responsible for a number of human deaths, especially in southern Brazil.

Wrap Up

Woolly bear caterpillars are harmless to humans, but one should never try to handle these creatures recklessly.

The hair present in the body can cause problems like severe irritation. Also, if your pet swallows one, it will encounter problems like coughing and gagging.

Therefore always be cautious around these caterpillars. Thank you for reading the article.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. 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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  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

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9 Comments. Leave new

  • Hi Mirta

    The moth in your photograph matches a published figure of Chlanidophora patagiata Berg, described by him in 1877 in the Bulletin de la Société Impériale des Naturalistes de Moscou, volume 52, page 9.

    It was described from a male specimen from Carmen de Patagones ands the holotype specimen is supposed to be in the Museum in Buenos Aires.

    I’ve not been able to find out much more about it but there is a note about its biology (Bourquin, F. 1949. Notes sobre la metamorfosis de Eugliphys bridarolliana Kohler 1949 Lep. Fam. Lasiocampidae – de Chlanidophora patagiata Berg 1877 Lep. Fam. Arctiadae – de Heliconius phyilis F. 1775 Lep. Fam. Heliconiidae – de Cucullia heinrichi Kohler. Acta zool. lilloana, Tucuman 7: 385-391).

    As Julian has mentioned, its taxonomic position is not fully resolved so there is scope for further reaearch on this, and related, species. It may be related to some species of noctuid currently placed in the subfamily Glottulinae.

    I hope that this helps.

    Best wishes

    Martin (Lepidoptera Curator, NHM London)

  • That is an exceptionally good pic of the wooly bear. I just saw one by my transformer at work and was wondering what they do for hibernation, so this answers my question! I also always thought they turned into Monarchs, but now I know otherwise…

  • Wow its November 4th and I found one on my lawnmower wow its November and no snow caterpillars and ladybugs all over

  • We live on the coast just south of sf – we had a vestal tiger moth perched on our front porch this last weekend

  • Do wooly bears that look like this have stinging hairs like other fuzzy/furry caterpillars do?

    • We know of no reactions to hairs of woolly bear caterpillars, but we suppose it is always possible that some person might have an allergic reaction to anything.

  • Just photographed one in Placentia, California

    • Karoline Robbins
      April 16, 2018 10:17 pm

      Hi Paul, I came here to identify a moth that I saw today, which I believe is in fact a Vestal Tiger Moth. Looking at your beautiful photograph, I think that yours is a Salt Marsh moth based on the striped legs and the yellow chest, a bit of which I think I see in your photos. I originally thought I had a Salt Marsh moth, but soon realized it was a Vestal Tiger moth because of the lack of stripes on the legs. Did you get more shots of it? It is gorgeous.

  • Just photographed one in Placentia, California


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