White Woolly Bear Caterpillars – All About Them

Numerous hairy caterpillars appear in the fall but do not cause much damage during this time; some hairy friends are the white woolly bear caterpillars.

Hairy caterpillars are a curious sight most people want to know what they are and if they are harmful in any way.   From a distance, the caterpillars can appear inviting.  They come with variable colors and tufts of hair protruding from their bodies.

The best advice to follow for any unknown insect is to avoid touching it or making any contact unless you are familiar with the species.

Identifying these hairy caterpillars in the fall is challenging.  They come in a range of colors from white to bright yellow, even within the same species. To be able to identify these caterpillars, you will require a prepared specimen with a microscope.

Here we will discuss the few common hairy caterpillars found in the fall.

Hickory Tussock Moth – (White Woolly Bear Caterpillars)

Also known as the white woolly caterpillar or white woolly worm, this worm is white with a black line down its back.  Some of them can be all white without the black line and are called albino woolly bear caterpillars.

Some appear to have tiny black spots instead of a black line; sometimes, the black line appears more like individual tufts than a line.  This worm also has four small areas with a very thin cluster of black hairs longer than the rest of the fuzz.  These are called pencils and are found on each corner of the body.

Hickory Tussock Moth - (White Woolly Bear Caterpillars)

Though not a true worm, the white woolly worm is found in the eastern U.S. and Canada. The hickory tussock caterpillar has been reported to be poisonous, but the worst reaction is a skin rash if you touch one of the woollies.

Its favorite diet is oak, walnut, maple, and ash leaves.  Just like their cousins, the yellow-spotted tussock caterpillar, the white woolly worm loves to live in clusters of longer bristles that stick out, in either black or white.

Banded Tussock Moth

Another late summer or early fall caterpillar is the banded tussock (Halysidota tessellations), another hairy caterpillar.

Its larvae show variable color patterns, but it is mostly yellow or white hairy bodies.  Its paired tufts of black and white bristles on the front and back and a tan to an orange horizontal line on its head tell it apart easily.

These caterpillars feed on the leaves of multiple shrubs and deciduous trees and shrubs in Michigan.  They are easy to find on the upper surfaces of leaves.

This species has only one generation, with mature caterpillars coming as early as July in the southern parts of Michigan state.

Woolly Worm Or Woolly Bear Caterpillars

The woolly worm or woolly bear (Pyrrharctia isabella) is popularly known for its weather prediction. It is the caterpillar that people tend to look for a weather forecast for the coming winter.   The traditional story followed by many today says that the narrower the rust-brown stripe, the harsher the winter.

Some caterpillars may lack brown stripes due to genetic diversity.  Larvae are usually black, with the central brown stripe widening to a variable degree as the woolly bear grows into later life stages.

The woolly bear has 2 generations annually, but the fall one is most noticeable.  They will be all over looking for a protected location to spend winter.  They love to spend winter under leaves or other plant debris.

When spring comes, the insect thaws and life resumes as normal.   The woolly worms are about 2 inches long and have a diverse diet in the late summer and fall, consisting of grasses, leaves like birch or maple, flowers like clover, sunflowers, and asters. Their damage is minimal and hardly recognized.

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American Dagger Moth

This caterpillar is either white or yellow, with five distinct tufts of long black hairs shooting from its body, attracting attention every fall.

The American dagger moth (Acronicta Americana) loves to rest on the lower side of the leaves with its head curled over to one side. This behavior differentiates them from the banded tussock moth caterpillar that rests on the upper leaf surface.

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They feed on various hardwood tree species and are commonly found in forests or among trees in the backyard, starting from August to October.  They are not known to cause economic damage to plants.

What To Do When You Encounter These Hairy Caterpillars

Now that we all know they appear in the fall, it’s best to avoid touching them by all means.  Some hairy caterpillars are known to have urticating hairs that penetrate the skin with ease.

These hairs can break off easily and puncture your skin, causing injury or irritation.  Remember, the hairs are microscopic and cannot be easily seen on your skin.

Some people experience severe allergic reactions after coming into contact with these worms.  The degree of severity depends on an individual human’s physiology.

The irritation they cause to humans is a natural defense mechanism against their predators.  Overall, do not touch these caterpillars, no matter how pretty they may look to you.

If you must touch them, put on a pair of gloves first before touching them.

What To Do When You Encounter These Hairy Caterpillars

What Does a White Woolly Caterpillar Mean?

These are the larval stage of various moths. They tend to be covered in furry hair that is defensive – it is spikey and will break off in your skin irritating it. With repeated exposure to these woolly hairs, some people can develop skin allergies that cause red skin reactions.

Should You Kill a Woolly Bear Caterpillar?

Generally, the answer is no – they cause minimal damage to your plants and are part of the natural ecosystem. 

Are Woolly Bear Caterpillars Endangered?

 You can see the conservation status of the Isabella Tiger moth or banded woolly bear caterpillar across most of North America. It appears in general that the populations of this moth are secure and under no major threat. 

How Long Do Woolly Bear Caterpillars Live?

The eggs laid by adults hatch in the fall, and the larval caterpillar stages overwinter and then emerge the next season to complete their lifecycle, metamorphosis, and emerge as adult moths that can lay eggs. Depending on how long your winter is, will govern the total life of the species. But work on 6-8 months of being alive (quite a bit of that being frozen).

They have a curious ability to allow their body to freeze slowly in such a way that it is not damaged in the caterpillar stage. In the case of the Arctic Wooly Bear Caterpillar, the growing season is really short. These caterpillars can therefore undergo a growth cycle where they can freeze and then thaw and get a bit of time in to eat and grow, and then freeze again. This means that they can take 7-13 years to make it from the caterpillar to the adult stage. The majority of this time they are however frozen.

Do White Fuzzy Caterpillars Turn Into Butterflies?

Generally, they turn into moths. These are similar to butterflies except their wings fold back and they often have a nocturnal nature. We tend to notice butterflies a lot more as they flutter around on flowers during the day. Moths are more difficult to notice as they are often not seen as much because of their nocturnal nature.

Where Do You Place a Woolly Bear Caterpillar?

Generally, just leave it where it is. They have little bristles that can break off and penetrate your skin – with time your body can develop an allergy to these and you will get an itchy patch. They have a wide range of plant species they can eat, so if you find one on some concrete, you can pick it up using a leaf and put it in a clump of bushes. 

How Big Do Woolly Bear Caterpillars Get?

The caterpillars will grow to about 2 inches in length before they spin a cocoon and metamorphosis allows them to turn into adults. This is a general rule an there is quite a bit of variation around this size.


Nature is beautiful!  And to see these white woolly bear caterpillars in various colors confirms how breathtaking nature is.

Human interruption is what causes these and other important creatures to diminish on planet earth.

These worms pose no harm to anyone; they are just an addition to beautiful nature.  Nature knows to introduce new things and when to exit the stage.  They love to hang around plants and trees of their liking with little to no interruption to humans.

We should treat them the same way – no interruption at all unless need be.  And even when the need arises, it’s best to handle them with care and allow them to enjoy this planet together with us.

Life would be so boring without these and other unique creatures. Make a better organic world for us all to live happily.    Enjoy your gardening journey!


What happens if you touch a wooly bear caterpillar?

A caterpillar’s skin is actually made of many small hairs called setae (pronounced “set-a-AY”).

These setae are incredibly flexible, and when the caterpillar is moving, it can use these hairs to stick to surfaces or other objects. The setae on a caterpillar’s back are arranged in rows, and each row contains a different kind of setae.

Some people have allergic reactions to caterpillars that are common in their area.

What does woolly bear caterpillar turn into?

It's a cocoon. The pupa stage lasts from about 2 weeks to 6 months, depending on the species. During that time it's a cocoon and doesn't look like anything else. After that time, the chrysalis emerges as a moths.
The woolly bear caterpillar is a larva of the tussock moth (Oecophora bractella). It is now found throughout much of Europe and North America, as well as in New Zealand and Australia.  The caterpillar has a brownish-grey body with a grey head. The body is covered by long hairs, which are also present on the head.

Are woolly bear caterpillars harmful?

The woolly bear caterpillar, a large brown moth with white spots on its back, can be found throughout the southeastern United States. It is not known to cause any serious problems for humans or their pets. However, if you come across a woolly bear caterpillar, try to avoid handling it, and remove it from your property immediately.

The woolly bear caterpillar is not known to carry any diseases that pose a health threat to humans. If you find it on your lawn or in your home, it will probably leave by feeding on flowers or other plant material. Do not touch it or allow it to escape onto your property. Remove it from your lawn or other plants as soon as possible.

What do woolly bear caterpillars like to eat?

They are omnivorous, but usually eat more insects than plants. They are omnivorous and feed on a variety of foods. They primarily eat insects, but will eat plants, berries, fungi, small animals, birds, and eggs. But they are not just eating insects; they are also eating other small invertebrates such as worms and ants. The caterpillars of the brown bear, Ursus arctos, live in groups on the ground, where they forage for food.

Can you pick up a woolly bear caterpillar?

Yes, you can pick up a woolly bear caterpillar. Woolly bear caterpillars are the largest caterpillar in North America.

Can you keep a woolly bear caterpillar as a pet?

Yes, you can keep a woolly bear caterpillar (Pycnoscelus) as a pet. They are not a moth, but they do have wings. They are native to North America, and are commonly found in the forests of the eastern half of the continent. It is possible that you will be able to find one in your area.
If you feed it, it will eventually pupate and become a butterfly.
They are usually nocturnal feeders, but they are also known to eat fruits and berries, as well as flowers. If you take care of them properly, they will grow into very large, fuzzy creatures. They will be about the size of a human thumb, and their skin will be about the thickness of a pencil lead.