Isabella Tiger Moth Poisonous? Unraveling the Myth

The Isabella tiger moth, also known as the woolly bear or woolly worm, is a well-known species due to its distinctive caterpillar stage. These fuzzy caterpillars have dense, stiff hairs and are usually black on the ends of their bodies and rusty red or brown in the middle. The adult moth has a wingspan of about 2 inches and its color ranges from yellow-brown to orange-brown, with some specimens featuring red-orange fringes on their wings (source).

While the Isabella tiger moth caterpillars may look intimidating due to their “hairy” appearance, they are not poisonous or harmful in their natural state. However, it is important to note that touching the bristles of the caterpillar can cause dermatitis or skin irritation in some individuals (source). To stay on the safe side, these caterpillars should be admired from a distance rather than handled directly.

Isabella Tiger Moth Overview

Species and Classification

The Isabella Tiger Moth, also known as Pyrrharctia isabella, belongs to the Lepidoptera order of insects. This order includes Butterflies and Moths, and the Isabella Tiger Moth falls within the Arctiinae subfamily, which is commonly referred to as Tiger Moths.

Habitat and Distribution

Isabella Tiger Moths inhabit various regions across North America. Their presence spans across the United States and Canada, making them quite widespread.

Physical Characteristics

  • Wingspan: The Isabella Tiger Moth possesses a wingspan that measures up to 2 inches.
  • Forewings: Their forewings feature a yellow or tan color, with pointed edges and faint lines. Small dark spots may also be present.
  • Hindwings: Female Isabella Tiger Moths have lighter-colored hindwings, which display an orange hue.

Isabella Tiger Moth and Virgin Tiger Moth Comparison:

Feature Isabella Tiger Moth Virgin Tiger Moth
Wingspan Up to 2 inches Up to 2.6 inches
Forewing Color Yellow or tan with faint lines Yellow-brown
Hindwing Color (Female) Orange Similar, but lighter
Caterpillar Type Woolly bears Woollybear

Life Cycle and Behavior

Eggs

Isabella tiger moth females lay their eggs on various plants. They hatch into caterpillars, also known as woolly bears or woolly worms, within a few weeks.

Larvae, and Pupae

  • Larvae: Woolly bear caterpillars are fuzzy with dense, stiff hairs. They usually have black ends and a rusty red or brownish middle. Touching their bristles may cause dermatitis in some people.
  • Pupae: The woolly worm’s larval stage ends when the caterpillar forms a cocoon around itself. In this cocoon, metamorphosis occurs turning the woolly bear into an adult Isabella tiger moth.

Adult Moths

Adult Isabella tiger moths have yellow or tan forewings with faint lines and small dark spots. Females have lighter hindwings that are orange. They are harmless to humans and not considered poisonous.

Seasonal Activity

The Isabella tiger moth’s life cycle involves a unique overwinter survival strategy for its caterpillars.

  • Woolly bears emerge in the warmer months, seeking out plants as a food source
  • As winter approaches, they find a suitable location to overwinter, like in wood piles or other insulated habitats
  • During hibernation, their body fluids partially freeze, allowing them to survive extreme cold
  • When the weather warms up, woolly bears resume feeding and eventually metamorphose into adult moths

Diet and Host Plants

The Isabella Tiger Moth, also known as the Woolly Bear or Woolly Worm, primarily feeds on herbaceous plants during its caterpillar stage. Some common plants the caterpillar enjoys include:

  • Clover
  • Maple
  • Elm trees
  • Grasses
  • Sunflowers

These caterpillars are often found in various habitats, such as grasslands or areas with dense vegetation. Their host plants mainly consist of herbaceous plants and a few trees. While they have a diverse diet, it’s interesting to note some key differences in their preference for food plants:

Food Plant Preferred by Banded Woolly Bear Preferred by Other Caterpillars
Clover Yes Varies
Maple Yes Varies
Elm Trees Yes Varies
Grasses Yes Varies
Sunflowers Yes Varies

An essential aspect of the Isabella Tiger Moth’s diet is that it is not poisonous. They do not pose any threat to humans, pets, or other animals. However, it’s vital to differentiate between the harmless Woolly Bear and potentially hazardous plants like poison ivy which may coexist in the same environment.

In summary, the Isabella Tiger Moth’s diet consists of:

  • A variety of herbaceous plants and trees
  • Non-poisonous characteristics
  • Preference towards clover, maple, and elm trees, among others

Poisonous or Not

Toxicity

The Isabella tiger moth, often known as the woolly bear or woolly worm, belongs to the family Erebidae and is not poisonous or toxic. Adults have yellow or tan forewings, while the larvae have black and brown hairs.

Dermatitis and Rashes

While not toxic, some tiger moths have hairs or spines that can cause skin irritation. However, the Isabella tiger moth does not have such hairs or spines, making it safe to handle without causing rashes or dermatitis.

Here is a comparison of the Isabella tiger moth and other tiger moths:

Feature Isabella Tiger Moth Other Tiger Moths
Poisonous No Varies
Hairs or Spines No Yes
Can cause rashes No Yes
Belongs to family Erebidae Yes Yes

Isabella tiger moth characteristics:

  • Non-poisonous
  • No harmful hairs or spines
  • Family Erebidae

Predators and Defense Mechanisms

Isabella tiger moth, also known as the woolly bear or woolly worm, has unique features that help protect it from predators.

Natural enemies

  • Predators: birds, bats, frogs, small mammals
  • Herbivores: leaves of grasses and other plants as food

Camouflage

  • Caterpillars: black ends and rusty red or brownish middle
  • Adult moths: yellow or tan wings with faint lines and small dark spots

Defense mechanisms

  • Sharp bristles: touching can cause dermatitis in some people
  • Rolling up: when disturbed, they curl into a ball

Comparison between caterpillars and adult moths

Feature Caterpillars Adult Moths
Color Black ends, rusty red/brown middle Yellow or tan wings, faint lines, small dark spots
Size Small, can curl into a ball Medium to large, wingspan varies
Defense Sharp bristles, rolling up Camouflage, avoiding predators

The Isabella tiger moth utilizes various defense mechanisms and camouflage techniques to ensure its survival in nature.

Cultural and Folklore Significance

Woolly Worm Festivals

Woolly bears, the caterpillar stage of the Isabella tiger moth, have long been a part of American folklore. They are believed to predict the severity of the upcoming winter based on their coloration. The more black segments and the fewer rusty red ones, the harsher the winter is expected to be.

While there is no scientific evidence to support this belief, it has led to the creation of several Woolly Worm festivals across the United States. These festivals usually take place in the fall and often feature woolly bear races, where participants encourage the fuzzy caterpillars to reach a finish line the fastest.

At these festivals, you may find:

  • Woolly bear races
  • Arts and crafts
  • Food vendors
  • Live music

Although the Isabella tiger moth is not considered poisonous, touching their bristles may cause dermatitis in some people. It is essential to handle them with care and never put them in your mouth, as doing so can lead to discomfort and potential health issues.

To sum up, woolly bears are not only a part of folklore and fun festivals; they can also serve as a reminder to be cautious when handling certain insects.

Scientific Study and Literature

The Isabella tiger moth is known for its larvae called “woolly bears” or “woolly worms.” However, not much scientific literature exists on its potential poisonous nature. Some studies focus on its growth, development, and survival.

Characteristics

  • Adult moths: Uniform light to medium orange brown forewings, with faint lines and spots on them 1.
  • Larvae: Black and chestnut colored bands2.

A related moth, the Virgin tiger moth, has been studied in-depth due to its similar appearance and fuzzy offspring3. However, no concrete information exists on the Isabella tiger moth’s toxicity.

Conservation and Distribution

The Isabella tiger moth (Pyrrharctia isabella) can be found across:

  • Canada
  • United States (excluding Hawaii)
  • Alaska
  • Missouri
  • New York

Throughout the United States, this moth is found in a variety of habitats, such as forests, meadows, urban areas, and farmlands. Its distribution stretches from the Southeastern United States all the way north to Canada1.

The Isabella tiger moth is not a butterfly but belongs to the tiger moth family. Adult moths have distinctive yellow or tan pointed forewings, often with faint lines and small dark spots2. They’re easily confused with butterflies due to their colorful wings, but they’re far more fuzzy.

Features of Isabella Tiger Moth

  • Yellow or tan pointed forewings
  • Faint lines and small dark spots on wings
  • Hindwings lighter and orange in females
  • Reddish-orange bases on forelegs3

These moths don’t seem to be endangered or threatened. As such, no specific conservation measures have been established.

Interestingly, the Isabella tiger moth’s larval stage, the woolly bear caterpillar, is more well-known than the adult moth. These caterpillars are often found crossing roads in search of food, such as noxious weeds, making them helpful in controlling invasive plant species.

In conclusion, the Isabella tiger moth is an intriguing insect that seems to be safe and secure throughout its wide range of distribution, and its caterpillar form is even beneficial in controlling noxious plant life.

Interactions with Other Species

The Isabella Tiger Moth is a common species found in the US and can interact with various other species in its environment. A notable interaction is with parasitic wasps. These wasps prey on the larvae or “woolly bears” of the Isabella Tiger Moth.

Parasitized woolly bears have a lower chance of survival, as the wasp larvae feed on their hosts. This parasitic relationship can greatly impact the population of the Isabella Tiger Moths in specific areas.

Another essential aspect of the Isabella Tiger Moth is the presence of setae or bristle-like hairs on the bodies of their larvae. These setae can sometimes cause dermatitis in some people when touched, but they generally aren’t considered harmful or poisonous to humans.

To better understand the interactions among these particular species, let’s examine a few key points in a comparison table:

Entity Isabella Tiger Moth Larvae Parasitic Wasps Humans
Effects Suffer from parasitism Beneficial, control moth population Possible dermatitis from setae
Role Prey Predator Potential threat to larvae

In summary, while Isabella Tiger Moth larvae do have interactions with other species, particularly parasitic wasps, they are not considered poisonous to humans. However, their setae can cause skin irritation in some cases.

Footnotes

  1. (https://pnwmoths.biol.wwu.edu/browse/family-erebidae/subfamily-arctiinae/tribe-arctiini/pyrrharctia/pyrrharctia-isabella/) 2

  2. (https://mdc.mo.gov/discover-nature/field-guide/isabella-tiger-moth-woolly-bear-woolly-worm) 2

  3. (https://uwm.edu/field-station/virgin-tiger-moth/) 2

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Caterpillar Hairs produce human rash!!!

 

Subject: ugly, painful rash from a cocoon
Location: Nitro, WV
November 14, 2012 11:55 am
Hi,
Two nights ago i tried on an old pair of pants that i kept in my basement closet. when i put them on i felt sting in my thigh that felt like a splinter and as i walked toward my mirror i felt a whole bunch of those stings so i ripped the pants off thinking there were bees in my pants or something. I immediately had a burning itchy rash all over my thigh. i looked in my pants to see if there were any bugs but all i noticed was group of small fibers that i thought maybe somehow my cat brought in stinging nettle hairs. Then this morning i noticed the cocoon in the floor where i tried the pants and realized that is what it was. I still have a rash 2 days later and its miserably itchy. I am curious to know what the cocoon is and how to make sure i get this insect far away from my house. Thank!
Signature: Lisa [Ed. Note:  Name withheld upon request]

Possibly Arctiid Cocoon

Dear Lisa,
Our first instinct is that this is the Cocoon of a Tiger Moth in the subfamily Arctiinae.  We didn’t search for an exact match, and though the color is wrong, this image from BugGuide shows the general form or cocoons in the subfamily.  We didn’t realize that Woolly Bears as the Arctiinae caterpillars are commonly called, had utricating hairs.  We have not noticed Woolly Bears in lists of stinging caterpillars we have linked to in the past.  The Ark in Space website is especially nice.  We wondered if perhaps this might be the cocoon of an Asp, but this image from BugGuidelooks very different.

Rash caused by Caterpillar Hairs

We will continue to research this matter to see if we can learn anything about the identity of the cocoon that gave you a rash.

Utricating Hairs

 

Letter 2 – Banded Woolly Bear

 

Subject: Woolly Bear Caterpillar
Location: Corvallis, OR
October 14, 2013 5:29 pm
Dear Bugman-
My three year old daughter and I have found two of these caterpillars. I believe that they are Isabella Tiger moth woolly bears. We have been feeding them plantain and dandylion greens and are concerned that we might not be providing the correct diet. They are eating the plantain leaves. I read that they eat Alder leaves- though there are no such trees in the immediate location in which we have found caterpillars. Do you have any suggestions? They will be over wintering on our patio in a screen topped jar.
Signature: Gwen’s Mommy

Banded Woolly Bear
Banded Woolly Bear

Dear Gwen’s Mommy,
You have correctly identified this Banded Woolly Bear as the caterpillar of the Isabella Tiger Moth.  It sounds like you are providing the correct habitat for them.  If they are eating plantain, you should be fine.  According to BugGuide:  “Larvae eats many plants and trees including grasses, asters, birches, clover, corn, elms, maples and sunflowers.”  They will most likely pupate soon.

Thank you!  We are looking forward to observing the process!

Letter 3 – Banded Woolly Bear: A mild winter in Minnesota???

 

Subject: catepillar
Location: mn
December 8, 2012 4:40 pm
found this in the snow in minnesota today can i keep it alive all winter?
Signature: sb

Banded Woolly Bear

Dear sb,
Even though your photo is out of focus, the markings and coloration on this Banded Woolly Bear, the caterpillar of the Isabella Tiger Moth,
 Pyrrharctia isabella, are unmistakeable.  According to BugGuide:  “The second brood overwinters as a caterpillar and pupates in Spring.”  In order for this individual to survive the winter and mate in the spring, you need to keep it cool.  We would recommend a sheltered location that is protected from the elements, but not heated, like a garage or unheated porch.  Keep it in a small aquarium or large jar with air circulation provided by a screen or other air permeable cover.  A small cardboard box would also suffice.  According to folklore, the relative size of the red band is indicative of the severity of the winter.  According to CirrusImage:  “Common folklore has it the severity of the coming winter can be predicted by the amount of black on the banded woolly bear, the Isabella tiger moth’s caterpillar. However, the relative width of the black band varies with age, and has nothing whatsoever to do with weather (Wagner 2005). Isabella tiger moth caterpillars overwinter, surviving freezing weather by producing their own antifreeze, with which their cells are infused.”   The Farmer’s Almanac website has a very thorough explanation of this lore, and it posits:  “According to legend, the wider that middle brown section is (i.e., the more brown segments there are), the milder the coming winter will be. Conversely, a narrow brown band is said to predict a harsh winter. But is it true?”  If the legend is true, your caterpillar would indicate a mild winter.

Authors

    by
  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com 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.

  • 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.

16 thoughts on “Isabella Tiger Moth Poisonous? Unraveling the Myth”

  1. I had exactly the same thing happen to me two days ago in the Snowy Mountains, Australia. The picture of the Arctiid Cacoon looks exactly like what fell out of my jacket sleeve.

    Reply
  2. We found a Isabella Tiger Moth Caterpillar in our driveway. We have put him in our butterfly habitat to watch it turn into a Moth. Can we feed it spinach and kale as its now late fall and most leaves have turned brown and our yard has been sprayed?

    Reply
    • According to BugGuide: “The first of two broods pupates in Summer. The second brood overwinters as a caterpillar and pupates in Spring.” With winter hibernation, the caterpillar will not need to feed. Keep the temperature of the habitat cool to prevent early emergence.

      Reply
  3. I had this happen yesterday, I accidentally stepped on it inside my left shoe it was so itchy in all over my left foot and leg till now , the spines struck all over my foot i can’t remove it because its too deep.
    Please reply this comment and give any information to handle this, will my foot be okay if i don’t remove the spines? Will it be removed by the body by time? Thank you

    Reply
  4. I had this happen yesterday, I accidentally stepped on it inside my left shoe it was so itchy in all over my left foot and leg till now , the spines struck all over my foot i can’t remove it because its too deep.
    Please reply this comment and give any information to handle this, will my foot be okay if i don’t remove the spines? Will it be removed by the body by time? Thank you

    Reply
  5. I was cutting a nearly dead Popular tree down in my front yard in late Dec. (Quabbin Reservoir region of central MA) The days were warm but the night were below 32F. After dropping the tree I noticed rash on the inside of my wrist just above my palm (near all those veins you can see) Within an hour, my wrist swelled to the point of limited movement and the rash became very high in shape. It’s shape was that of a cocoon or a caterpillar body and there were a great deal (100 or so) small red prick marks surrounding the worm like rash all around it. I went inside and washed it and put some witch hazel on it and then slowly over 36 hours it mostly went away. Since then, I thought I had the flu,,,,recognizing my symptoms 3 weeks later are spot on to what I have read about the PERNICIOUS PUSS stings (not saying it was this insect yet the symptoms do match). headaches, nausea, vomiting, intense abdominal distress, lymphadenopathy, lymphadenitis. I’ve had all of this without a fever. I’m feeling better slowly yet there was a point that I could not even speak, I thought I had Laryngitis….horrible swelling of all of the glands in my neck, lasted about 4 days, started out a day or so after the bite and grew to extreme discomfort after 4 days….. NOt sure if there is any treatment this late in the game yet i’m heading to the doctor

    Reply
    • I had a cocoon in my shoe unbeknownst to me and I was barefoot. Within 4 hours of removing shoe the top of my foot was swollen , red to the shape of cocoon, so much pain and itch I could hardly stand it . After 2 doc appts they said I was having an illergic reaction to the venom. I was put on prednisone and a steriod cream. I been taking this treatment for 7 days. Symptoms are now just starting to ease up. Shoes are now in garbage.

      Reply
  6. I had a similar cacoon fall out of a container I had long stored in the garage. It fell on my arm and stuck to it. When I brushed it off little tiny hairs stuck to my arm and a rash appeared within a half hour. 2 weeks later and though the rash has gone down a little it still itches like crazy! I live in NW PA with a large population of Wooly Bears.

    Reply
  7. I just had one of these buggers stuck on my shoulder! Ah! I live in the southern tier of NY. My arm is all tingly. I’m a little freaked out. I used tweezers to pick out what I can but still some stuck in.

    Reply
  8. I came into contact with this 5 days ago. It was on the back of a chair and I rested my back on it for about 10 minutes before I felt stinging/prickling! That night it was a bunch of tiny red dots. Now they are bigger red marks and are itchy! I went to the doc today and got some ointment for it. Hoping that helps the itching and reduces the swelling. Also hoping I don’t experience any more symptoms as time passes!

    Reply
  9. I just came in contact with one of these cocoons; the cocoon was inside my oven mitt and when I put my hand inside the oven mitt I got hundreds of tiny splinters in two fingers. Those fingers are now swollen and very, very itchy! To those of you who have had this happen before, did you try Benadryl? I was planning to start there and hopefully get some relief.

    Reply
  10. There was a tornado so I went downstairs to sit on my couch. When I got up to pee, my leg was hurting bad so I went to look in the mirror. When I saw that there was a patch of redness, I felt it. It felt like small fibers stuck! I then take duct tape and rip the fibers out which gave me relief considering the fibers made it hurt when I walked. 2 days later , it’s exaclty like the picture of the rash shown above and I don’t know what to do. What helps people in the past that had this happen.

    Reply
  11. My 2yr old had this happen recently. I put her boots on and she started complaining about her foot saying it hurts and something is in her boot. I removed the boot and started hitting it against the concrete and a fuzzy cocoon fell out. I was unfamiliar with it so I started stepping on it and crushed it trying to see what was inside. When I look at her foot there were tiny hairs all over it I could not pick them out but it worked when I brushed them off in a sweeping motion. The rash may have developed the same day but I did not notice until the next morning. She did scratch often???????????? and it is still there but she hasn’t scratched as much today. I tried the baking soda paste cool water to relieve the itching and information and I have tried cream. I will take her to the doctor tomorrow. It was scary at 1st not knowing what caused until I thought back about the boot. Ugh it was bad, hope it NEVER happens again

    Reply

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