Woolly Bear Caterpillar Life Cycle: From Egg To Moth

In this article, we shed some light on the woolly bear caterpillar life cycle and explain what this caterpillar becomes when it finally grows up.

There are a lot of myths attached to the different insects scattered throughout the world. One such myth is connected to the woolly bear caterpillars.

People in many parts believe that they can be used to predict the intensity of the upcoming winters.

Woolly Bear Caterpillar Life Cycle

This entire idea is based on the body color and patterns of stripes on these insects. But can they actually predict the weather?

To get this answer, we must learn more about the woolly bear caterpillars and especially understand their life cycle and how it is impacted by weather.

In this article, we talk about this and also find out if the stories and myths are true.

What Are They?

Woolly bears are the caterpillar form of the Isabella tiger moths (Pyrrharctia isabella). These caterpillars usually have a black-colored body with a reddish-brown band in the middle.

The body color changes according to the worm’s age and feeding intensity. Moreover, their bodies are almost entirely covered with a dense coat of fine hair.

In the United States, there are eight types of caterpillars that have dense hair coats on the body, and all of them are types of woolly bear caterpillars.

They have a wide variety of names, including banded woolly bears and fuzzy caterpillars.

You are most likely to spot these insects during autumn when they leave the food plants and search for warmer spots to hibernate throughout the winter.

Woolly Bear Caterpillar

What is Their Life Cycle?

A fully grown 1.5-inch fuzzy bear caterpillar becomes an Isabella tiger moth.

When winter arrives, the woolly bears usually creep into warm spots to hibernate throughout the winter.

Once the cold subsides, these caterpillars wake up from hibernation, and they spend a few nights feeding and gaining strength.

They eat leaves of flowering plants during this time and go through five instar stages of growth.

After that, they begin the pupating process. It takes around two weeks for the adult moths to come out of the pupa.

The adults are orange-yellow in color with a 2-inch wingspan. There are no markings on the wings, but you can spot three rows of black dots in the abdomen.

During the adult stages, these moths do not usually feed; they spend a few days in mating and laying eggs.

After this, they die. In a span of two weeks, the new batch of eggs hatches, and the cycle continues.

Woolly Bear Caterpillar

Where Are They Found?

Wolly bear caterpillars are found across the different regions of the United States, Mexico, and Canada.

Usually, these insects hatch twice a year, and you can spot them as an adult during spring when they emerge out of the pupa.

During winters, these caterpillars are often found hibernating in secluded, warm spots like rocks, fallen logs, and more.

During April-May, you can spot the cocoons of these insects in the same remote areas.

What Do They Eat?

Woolly bear caterpillars are predominately herbivores. They consume plants, herbs, and other food items. Given below are a few foods that these caterpillars eat:

Herbaceous plants

Woolly bears feed on low-growing plants that bear seeds. They prefer to eat leaves rather than eating blades of grass.

Plants like yellow dock, curly dock, clovers, dandelions, and violets are some of the plants that they love to eat.

At times they also eat leafy vegetables like spinach, sunflowers, cabbage, and more.

Grass, grains, and forb

If there are no leaves present, these insects shift to eating blades like grass, maize, barley, etc. However, they don’t feed on grass or other blades that have lost their green color.

Trees and tannins

At times the woolly bears can go top of trees to graze on leaves. They like to taste elm, maple, and birch tree leaves, but they often drift away from ornamental trees.

Woolly Bear Caterpillar

Woolly Bear Myth: Winter Predictors

The color and appearance of these insects are not the only fascinating thing about them; there are a bunch of myths attached to the woolly bear caterpillars.

People believe that these worms can predict the intensity of the upcoming winters.

If one finds a woolly bear caterpillar with a wide brown patch in the middle, the region will experience a soothing and mild winter.

However, if the caterpillar is entirely black, the winter will be harsh.

This myth is wrong, as the color of the body depends on the age and the feeding intensity of the caterpillar and has nothing to do with the oncoming winter.

In fact, if anything, it shows how well the caterpillar fed in the last season, and therefore it indicates how harsh or mild the previous winter was.

Frequently Asked Questions

How long does a woolly bear stay a caterpillar?

Usually, these caterpillars live for around two to four weeks before turn start pupating, but in some cases, the process can be much longer than this.
For example, the Arctic woolly worms take almost 14 years to complete this process.

Where do they go in the winter?

Woolly bear caterpillars often search for secluded and warm spots before the winter. Once winter hits, they shift to these places and start hibernating to be able to survive the winter.
Crevices of rocks and abandoned logs are some of the top spots these worms choose for the winter.

How do you keep a woolly bear caterpillar alive?

Woolly bear caterpillars need a lot to eat; therefore, if you want to keep them alive, you must keep supplying fresh leaves constantly to them.
Since it is not practical to get fresh leaves every time, you can keep their food leaves in a plastic bag stored in a jar of water and put it in the refrigerator. This will keep them fresh.

What month do woolly bear caterpillars come out?

The woolly caterpillars usually come out during the months of summer. However, there are two generations of these caterpillars that come out during the year.
The first batch comes out during the months of June and July, which is followed by the next set that comes out in September.

Woolly Bear Caterpillar

Wrap Up

Woolly bear caterpillars are usually tough to spot as they spend most of their time in the hibernation and pupation stages.

But if you understand their life cycle, you can know the exact time to spot these worms. Also, since they emerge as adults at two different times of the year, there is a higher chance of spotting as adult tiger moths.

We hope the article helped you understand the life cycle of these caterpillars. Thank you for taking the time to read it.

Reader Emails

If you are looking to keep the woolly bear caterpillar as a pet or are just fascinated with this bug, it is important to understand its life cycle and how it goes through different stages to reach its final destination – as a tiger moth.

Over the years, many of our readers have enquired about this intriguing caterpillar in various stages of its life, silently watching as the glory of nature unfolds before their eyes.

Do read some of these emails and experience the joy yourself!

Letter 1 – Newly Metamorphosed Wood Moth from Australia


What type of bug is this? December 18, 2009 Hi, my husband found this bug crawling up his leg. After his initial shock he snapped a photo. We were camping on the Nullabour Plain, South Australia. The climate there is very dry and hot, with little vegitation and very little water. The bug was about 40mm in length. It would be great to put a name to this amazing bug. jackie Nullabor Plain, South Australia
Unknown Newly Metamorphosed Moth
Newly Metamorphosed Wood Moth
Hi Jackie, This is a newly metamorphosed Moth whose wings have not yet expanded.  We believe it may be a Tiger Moth in the family Arctiidae, but we are not certain.  Perhaps one of our readers can supply a species identification. Update:  May 12, 2015 We just received a comment that this appears to be Endoxyla amphiplecta, or a related species and the image on ButterflyHouse looks very similar.

Letter 2 – Painted Tiger Moth laying eggs


devoted mom Location:  Los Angeles, CA October 19, 2010 12:34 am This little lady (or man) has been stationary for several days now on the outside of our house. I would normally think a bug that hasn’t moved for 4 days with such death grip is well, dead, but there are babies to protect, so I’m not quite sure. She’s a beauty! Any idea what she is? Signature:  Julie
Painted Tiger Moth laying eggs
Hi Julie, It is the right time of year with the correct weather conditions for the Painted Tiger Moths, Arachnis picta, to be flying, mating and laying eggs.  One was perched for several days on the door jamb of our Mt. Washington, Los Angeles offices for several days and she finally dropped dead without laying eggs.  A pair was spotted this morning on the fence post near the chicken coop and they were in the act of mating, and this evening, there was a female depositing eggs on the front porch beneath the porch light.  Nearly every year a female lays eggs under the porch light.  After a week or so, depending upon the temperature, the eggs will hatch into tiny fuzzy caterpillars that will disperse and begin feeding on many weedy type plants that sprout after the first rains.  The caterpillars are a typical Woolly Bear.  Adult Painted Tiger Moths do not feed as adults.  According to Charles Hogue in Insects of the Los Angeles Basin: “The mature larva is about 1 1/2 inches (40 mm) long and is densely covered with stiff black hairs; The head is black. The caterpillar feeds nocturnally on a great variety of weedy plants, including wild radish, Wandering Jew, and Acanthus. It hides during the day, sometimes retreating into the soil, and it rolls into a ball when disturbed, It develops during the winter and then is somewhat dormant (although active, it does little feeding) until late the following summer, when it pupates; on a warm fall evening, the adult emerges. Individual caterpillars occasionally pupate immediately after maturing and pass the summer in the pupal stage.”

Letter 3 – Cortalaria Pod Borer Metamorphosis from Guam


UPDATE ON CATERPILLARS Location: Guam July 24, 2011 9:54 pm Update from previous question to ID a caterpillar They’re moths, not sure what kind?! Signature: Holly
Tiger Moth: Argina astrea
Hi Holly, Thanks for the update, but we cannot find your original identification request.  We believe we have correctly identified your moth as Argina astrea on the Moths of Borneo website.  We are very interested in posting the photos of the caterpillars if you are able to resend them by attaching the images to this response.  We also want to commend you on successfully raising a caterpillar to maturity and taking photographs of the metamorphosis process.  The James Cook University website indicates that the common name, taken from the food plant, is the Crotalaria Pod Borer.
Tiger Moth Pupa: Argina astrea
Thank you! Wonderful information, I really appreciate it, I will be making a donation for your time! I have attached the photos of the plant we found them on as well as the caterpillars. Thank you again. Thanks, Holly Hutson
Crotalaria Pod Borer
Hi Again Holly, We are most excited to be receiving your caterpillar photos, and you are most kind to make a donation even though we missed your first request.
Crotalaria Pod Borer
The plant you submitted is definitely a Crotalaria based on the Virginia Tech Weed Identification Guide website.

Letter 4 – Milkweed Tiger Moth Caterpillar


Fuzzy caterpillars on my milkweed? Location: St. Paul, Minnesota August 22, 2011 4:25 pm Hi! I let some volunteer milkweeds grow in my gardens this year in hopes they’d attract a monarch caterpillar or two. Last night I was practicing my photography skills in my backyard and thought I might just check to see if I had any little monarch friends and found these fellas instead. I was hoping you let me know what I’m raising in my yard. I surfed through your butterfly and moth caterpillar pics and didn’t see these. Thanks! Signature: Heidi
Milkweed Tiger Moth Caterpillar
Hi Heidi, Monarchs are not the only insects with caterpillars that feed on milkweed.  Several moths including the Milkweed Tiger Moth Caterpillar or Milkweed Tussock Moth Caterpillar, Euchaetes egle, also feed on milkweed.  You can see additional photos on this species on BugGuide.

Letter 5 – Possibly Caterpillar of a Silver Spotted Tiger Moth


Subject: Caterpillar Location: Camp Royeneh, CA May 18, 2016 8:02 pm Could this be a silver spotted tiger moth caterpillar? I’ve read they are poisonous but the Boy Scout leader said this one wasn’t. It was found near Guerneville, CA. There were coastal redwoods, Douglas firs and Bay Laurels in the area. Signature: Toni
Possibly Silver Spotted Tiger Moth Caterpillar
Possibly Silver Spotted Tiger Moth Caterpillar
Dear Toni, We agree that this might be the Caterpillar of a Silver Spotted Tiger Moth, Lophocampa argentata, based on this and other BugGuide images.  According to BugGuide:  “Note of Caution: Like several kinds of wooly-bear-type caterpillars, these have venomous, stinging hairs, which can cause a burning sensation and/or a rash in sensitive people- look, but don’t touch!”  We believe the key words are “sensitive people” meaning most folks, including tough, young children, are not affected.

Letter 6 – Painted Tiger Moth Hatchlings, we suspect


Subject: SoCal larvae Location: Los Angeles, ca October 27, 2016 11:53 am Hi- i’m in i’m in Silverlake Los Angeles, ca. This is on the wall of my veranda. It’s a cluster of seemingly clear eggs with tiny teeny larvae around it. It’s currently the end of October. Weather just changed to cool. Signature: Dn
Probably Painted Tiger Moth Caterpillar Hatchlings
Probably Painted Tiger Moth Caterpillar Hatchlings
Dear Dn, These are hatchling caterpillars and all indications are that they are Tiger Moth hatchlings.  We suspect they are Painted Tiger Moth hatchlings because we live in nearby Mount Washington and there are currently Painted Tiger Moths flying to our porch light.  Painted Tiger Moths lay clusters of eggs, frequently on walls near lights, and the caterpillars, which are general feeders known as Woolly Bears, quickly disperse.

Letter 7 – Immature Painted Grasshopper from India


Subject: Grasshoppers Location: Seen at Chennai South India August 11, 2017 10:09 am Help me to identify the variety of the colour grasshopper. Signature: SUNDAR RAGHURAMAN
Immature Painted Grasshopper
Dear SUNDAR, Based on its bright coloration, we suspected correctly that this is a Toxic Milkweed Grasshopper in the family Pyrgomorphidae, but ascertaining the species identity took longer than expected because the nymph differs in coloration from the adult.  This is an immature Painted Grasshopper, Poekilocerus pictus, which we identified thanks to this FlickR posting.  We verified its identity on Jungle Dragon where it states:  “‘Poekilocerus pictus‘ is a large brightly colored grasshopper from India. Nymphs of the species are notorious for squirting a jet of liquid up to several inches away when grasped.”  We also located this Blog we cannot read, but that you might find interesting.
Immature Painted Grasshopper
Hi Daniel
Many thanks for your clarification on my query.  It’s very much interesting.
Thanks a lot.
Immature Painted Grasshopper

Letter 8 – Painted Tiger Moth Caterpillar Hatchlings


Subject:  Butterfly eggs? Geographic location of the bug:  Los Angeles, CA on side of wood door Date: 11/05/2017 Time: 03:31 PM EDT Hello, I noticed a gray moth about 1 inch big sitting on the side of my door outside.  Then, I noticed that it seemed like the gray parts were falling off and then an orange yellow butterfly was underneath. The next day, the butterfly was gone, but there were tiny dark silver eggs in a triangle shape. I thought it was just a remnant, but then 2 days later, these tiny little bugs started growing out of the eggs, and now the eggs are all gone. I’m just wondering what kind of bug they are and why the butterfly laid it on the door instead of a leaf.  Will they all die and should I do anything? Thank you. How you want your letter signed:  Lecia
Painted Tiger Moth Caterpillar Hatchlings
Dear Lecia, Based on your location, your description of the “gray moth” and the “orange yellow butterfly [that] was underneath” and the images of these newly hatched caterpillars, we are quite confident that the eggs were laid by a Painted Tiger Moth.  As an aside, a clutch of similar eggs hatched on our office screen door this week.  The Painted Tiger Moth is a pretty gray moth with reddish orange to yellow underwings.  Painted Tiger Moths are attracted to porch lights, and they frequently mate and lay eggs on the walls of homes that have lights that attract them.  Painting Tiger Moth caterpillar hatchlings look exactly like your images.  Painted Tiger Moths do not feed as adults and the female will die shortly after laying eggs.  It is possible the individual on your wall died and began to fall apart, first losing the wings which is why you thought the “gray moth” had a “orange yellow butterfly … underneath.”  Painted Tiger Moth caterpillars are generalist feeders that will eat a wide variety of weeds and other low growing plants in the yard.  For their first meal, they eat their egg shell and that provides them with the necessary energy to disperse in search of food.  It will save them a trip if you relocate them to a part of your yard with tender green sprouts, but they will also fend for themselves, though we imagine many will not survive. 
Painted Tiger Moth Caterpillar Hatchlings
Thank you so much.  I believe that you are right. Their eggs are completely gone now. I really appreciate it. I Will try to move them to some leaves.
Lecia Harmer

Letter 9 – Probably Painted Tiger Moth Caterpillar


Subject:  Black Bristly Caterpillars Geographic location of the bug:  San Diego, California Date: 04/24/2018 Time: 03:05 PM EDT Your letter to the bugman:  Dear Bugman, I have been finding these black bristly caterpillars every spring for 3 years in my backyard. They don’t have red or Orange bands so they aren’t Leopard Moth Caterpillars (Which is what ice been calling them). They have pale red/Orange bumps under they’re bristles. I have lots if questions so please write back asap! How you want your letter signed:  Savannah D.
Probably Painted Tiger Moth Caterpillar
Dear Savannah, This is the caterpillar of a Tiger Moth in the subfamily Arctiinae, the group that contains the Leopard Moth, though that is an eastern species.  Considering your location, we suspect this is the caterpillar of a Painted Tiger Moth, Arachnis picta, a species that is quite numerous at our Mount Washington, Los Angeles office.  Alas, our go-to site for identifications, BugGuide, has no images of Painted Tiger Moth caterpillars except newly hatched individuals, however, BugGuide does provide this description:  “Larva – covered in dense black and cinnamon-colored bristles.”  The adult Painted Tiger Moth is a lovely insect that is frequently attracted to porch lights.

15 thoughts on “Woolly Bear Caterpillar Life Cycle: From Egg To Moth”

  1. Hey! This was an informative post. I captured one of these little ladies because she was striking. She proceeded to lay about 300 eggs over a period of days. In fact she managed to escape from my container on the second night and laid some eggs high on a wall. I found her, thinking it was a different one, on the floor so I brought her back. Anyway it has been long enough, about a week and the little ones are coming out. I don’t know what they eat. And I don’t know their life cycle. I tossed in some mint leaves and blades of grass and the first batch of tiny caterpillars fell off the napkin where they had been laid onto the bottom of the container. What do your do? The ones which were laid on the wall near the porch light? Do they eventually drop/crawl to the ground to begin feasting on plants? Do these critters overwinter and where do the pupate?

    • According to Charles Hogue in Insects of the Los Angeles Basin: “The mature larva is about 1 1/2 inches (40 mm) long and is densely covered with stiff black hairs; The head is black. The caterpillar feeds nocturnally on a great variety of weedy plants, including wild radish, Wandering Jew, and Acanthus. It hides during the day, sometimes retreating into the soil, and it rolls into a ball when disturbed, It develops during the winter and then is somewhat dormant (although active, it does little feeding) until late the following summer, when it pupates; on a warm fall evening, the adult emerges. Individual caterpillars occasionally pupate immediately after maturing and pass the summer in the pupal stage.”

  2. Have you any experience with them? The little caterpillars emerged at the same time and remained within their cluster till I threw in some food in which they were knocked off the paper towel where they were laid. I have a second group that emerged late last night and are still in their cluster, about 20 hours post hatching. The first group remained in their cluster for at least 48 hours before they fell off. Many are feeding on the plants I threw in, some have climed up the eclosure.

  3. Last year 1 Painted Tiger moth came and laid eggs on our front door. Now we have 3 but only 1 (could be same as last year) is laying eggs, for now. Once the caterpillars hatch they will fall onto concrete and have a long way to go to dirt . Can we carefully pick the eggs off the door (once mother is gone) into a small container then drop in the surrounding flower beds once hatched? Please advise.

    • The egg laying moth from this year is not the same individual as the one you had last year. The first meal of the caterpillar is part of its egg shell. Though it has some distance to wander, the newly hatched caterpillars are quite capable of finding food. You should not attempt to dislodge the eggs. They may get damaged. If you want to try to locate caterpillars that have hatched, handle them with care.

  4. I found one of these on my milkweed. I saw caterpillar droppings and was hoping to find a monarch caterpillar. Instead, I found this. I live in southeast Michigan. Is this a beneficial insect or a pest?

  5. I had a moth lay eggs on the back passenger side fender of my jeep, they were bluish grey in color pictures attached dont show correct color, is it unusual for them to lay eggs on a vehicle that is driven everyday??

    • Certain species of Tiger Moths are opportunistic, and they will lay eggs in many unusual places. The caterpillars hatch and begin feeding on the egg shells before dispersing in search of appropriate feeding locations, and since many Tiger Moths are general feeders rather than being limited to a specific plant, the female is not compelled to locate suitable food plants when laying her eggs.


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