Flannel Moth Caterpillar Sting: Quick Facts and Prevention Tips

The flannel moth caterpillar, also known as the puss caterpillar or southern flannel moth (its scientific name is Megalopyge opercularis), may look soft and cuddly, but it harbors a painful secret. Covered in fine hairs and venomous spines, these caterpillars can deliver a nasty sting when touched, causing severe pain and discomfort. To understand the effects and risks associated with flannel moth caterpillar stings, it’s important to learn more about this deceptive little creature and how best to avoid it.

Puss caterpillars can be found on different types of foliage and small twigs, often blending in with their surroundings. As the caterpillar grows, the severity of its sting increases, according to Texas A&M University. Stings from this insect can cause extremely painful reactions and even lead to more severe medical complications. It is essential to be aware of their presence while spending time outdoors and know how to respond if stung by one of these fuzzy pests.

Flannel Moth Caterpillar Overview

Physical Appearance

The Flannel Moth Caterpillar, also known as the Puss Caterpillar, is a unique insect with a fluffy, furry appearance. These caterpillars have:

  • Soft, fur-like setae
  • Venomous spines hidden beneath the fur
  • A tail-like structure at the rear end

Life Cycle

The life cycle of the Flannel Moth Caterpillar consists of four stages: egg, larva, pupa, and adult. Here are some key facts about each stage:

  • Egg: Small, elongate, and covered with female moth hairs; laid in clusters on foliage or twigs (source).
  • Larva (caterpillar): Stings at all stages, but the severity increases with size (source).
  • Pupa: Develops into an adult moth after the larval stage.
  • Adult (Southern Flannel Moth): Covered with fluffy, wavy, flannel-like scales (source).

Flannel Moth Caterpillar vs Io Moth Caterpillar

Feature Flannel Moth Caterpillar Io Moth Caterpillar
Appearance Soft, fur-like Spiky and colorful
Sting capabilities Yes (venomous spines) Yes (urticating hairs)
Severity of the sting Increases with size Moderate to severe

Note: Both caterpillars can cause painful stings, but the Flannel Moth Caterpillar’s sting severity increases as it grows, while the Io Moth Caterpillar has a more consistent sting throughout its development.

Sting and Reaction

Mechanism of Sting

Flannel moth caterpillars, such as the puss caterpillar, have venomous spines hidden beneath their furry appearance. When these caterpillars come in contact with human skin, the spines break off and release toxins, causing the sting.

Symptoms and Severity

The reaction to a flannel moth caterpillar sting varies, ranging from mild to severe. Common symptoms include:

  • Pain: Stings can be intensely painful, sometimes described as similar to a wasp sting.
  • Redness and Swelling: The skin around the sting may become red and swollen.
  • Rash and Blisters: Itching, welts, and small blisters may develop at the site of the sting.
  • More severe symptoms: In some cases, people may experience nausea, vomiting, headaches, respiratory stress, or shock.

If the sting is on a sensitive area like the face, or if the person has an allergic reaction, the symptoms may be more severe and require immediate medical attention.

Comparing Flannel Moth Caterpillars

Caterpillar Sting Severity Physical Appearance
Puss Caterpillar Most severe among flannel moths Fluffy, furry, with venomous spines hidden
Black Wave Flannel Moth Less severe sting Color variation and long wispy hairs, but less venomous

For example, the sting from a black wave flannel moth caterpillar is generally less severe than that of a puss caterpillar.

Key Takeaways

  • Flannel moth caterpillars sting using venomous spines hidden beneath their fur.
  • Symptoms may include pain, redness, swelling, rash, blisters, and, in severe cases, nausea, vomiting, and respiratory stress.
  • Puss caterpillar stings are more dangerous than black wave flannel moth caterpillar stings.
  • Seek immediate medical attention if experiencing severe symptoms, an allergic reaction, or if the sting is near the eyes.

Treatment and First Aid

Immediate Remedies

If stung by a flannel moth caterpillar, there are several immediate remedies you can apply:

  • Gently remove the spines using a piece of tape or sticky side of a bandage1.
  • Wash the area with soap and water to minimize the spread of toxins2.
  • Apply a cold pack or ice wrapped in a cloth to reduce swelling and pain3.
  • Mix baking soda with water to create a paste and apply it to the affected area to soothe pain4.

Medical Care

For some individuals, a flannel moth caterpillar sting may require further medical attention:

  • Apply hydrocortisone cream or antihistamine to alleviate itching and inflammation5.
  • In cases of severe pain, over-the-counter pain relievers may provide relief6.
  • If symptoms worsen or last longer than a few hours, seek medical attention immediately7.

Here’s a comparison table of common remedies and when to seek medical care:

Remedy Immediate Use Medical Care Required
Remove spines Yes No
Wash with soap & water Yes No
Cold pack or ice Yes No
Baking soda paste Yes No
Hydrocortisone cream No Yes
Antihistamines No Yes
Pain relievers No Yes

Be aware that some individuals may have an allergic reaction to a flannel moth caterpillar sting, which includes symptoms like nausea, difficulty breathing, or shock8. If you experience any of these symptoms, seek medical attention immediately.

Prevention and Awareness

Geographical Distribution

The southern flannel moth caterpillar, also known as the puss caterpillar (Megalopyge opercularis), can be found primarily in the Southeast of North America, including Florida. Other stinging caterpillars like the saddleback moth caterpillar, spiny oak slug, buck moth caterpillars, and white flannel moth caterpillar can also pose health hazards and are similarly distributed.

Stinging caterpillar distribution:

  • Southern flannel moth caterpillar: Southeastern United States
  • Saddleback moth caterpillar: Eastern United States
  • Spiny oak slug: Eastern United States
  • Buck moth caterpillars: Eastern United States
  • White flannel moth caterpillar: North America

Stay Aware and Informed

To prevent stings from flannel moth caterpillars and their relatives, be aware of their potential presence. Recognize their appearance, which typically consists of dense setae or hairs that can contain venomous spines. For example, the southern flannel moth caterpillar has a fluffy appearance with gray or tan hairs.

Stinging Caterpillar Features:

  • Dense, hairy-looking setae
  • Venomous spines
  • Various colors and patterns

Entomologists recommend avoiding direct contact with all hairy or spiny caterpillars to minimize the risk of stings. When working in areas with known stinging caterpillar populations, wear protective clothing such as gloves and long sleeves.

Prevention measures:

  • Avoid direct contact
  • Wear gloves and long sleeves
  • Stay informed about local caterpillar populations

By staying aware of geographical distribution and the appearance of stinging caterpillars, you can better avoid and prevent potentially painful encounters.

Unique Species and Varieties

Stinging Rose Caterpillar

The Stinging Rose Caterpillar is a brightly colored, fuzzy caterpillar that can cause a painful rash when it comes into contact with skin. Some of the notable features of this caterpillar include:

  • Distinct black and orange-yellow stripes
  • Fuzzy hairs hiding venomous spines
  • Usually found on deciduous trees

If stung, applying an ice pack and using a counter-irritant, like calamine lotion, can help alleviate the pain. Severe reactions may require medical attention.

Io Moth Caterpillar

The Io Moth Caterpillar is another stinging variety with a unique appearance:

  • Bright green with red and white stripes
  • Two pairs of large, black horns
  • Feeds on a variety of plants, including garden favorites

The sting can cause symptoms like blistering, shortness of breath, difficulty swallowing, and abdominal pain. If these symptoms occur, seek medical help. The Io Moth itself has a wingspan of 2-3.5 inches and is typically cream-colored with eye-like markings.

Buck Moth Caterpillar

Lastly, the Buck Moth Caterpillar poses a risk to unsuspecting gardeners:

  • Black, fuzzy body with numerous spines
  • Can be found on oak trees
  • Leaves a painful caterpillar rash

Like the other varieties above, using an ice pack and a counter-irritant can help with the sting. However, severe allergic reactions may warrant medical assistance.

Comparison Table:

Species Color Location Sting Severity
Stinging Rose Caterpillar Black & Orange-Yellow Deciduous Trees Moderate Pain
Io Moth Caterpillar Green, Red & White Stripes Various Plants Severe Symptoms
Buck Moth Caterpillar Black with Spines Oak Trees Painful Rash


  1. https://citybugs.tamu.edu/factsheets/biting-stinging/others/ent-3010/

  2. https://content.ces.ncsu.edu/puss-caterpillar

  3. https://agrilifetoday.tamu.edu/2022/04/14/start-looking-out-for-stinging-caterpillar/

  4. https://www.ncbi.nlm.nih.gov/books/NBK539851/

  5. https://www.ncbi.nlm.nih.gov/books/NBK539851/

  6. https://www.ncbi.nlm.nih.gov/books/NBK539851/

  7. https://agrilifetoday.tamu.edu/2022/04/14/start-looking-out-for-stinging-caterpillar/

  8. https://agrilifetoday.tamu.edu/2022/04/14/start-looking-out-for-stinging-caterpillar/

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 – White Flannel Moth Caterpillar Stings Cousin


Subject: Caterpillar?
Location: Southeast Missouri
August 1, 2017 2:50 pm
My cousin found this in her bed one evening! She had a few spots on her arm and leg that stung. Could this be a type of stinging caterpillar?
Signature: Brittany

White Flannel Moth Caterpillar

Dear Brittany,
This is a White Flannel Moth Caterpillar and they do sting.  Here is a BugGuide image for comparison.  According to BugGuide, the caterpillars feed on “A variety of hosts reported including black locust, hackberry and redbud.”  Are any of those trees growing near your cousin’s bedroom?

White Flannel Moth Caterpillar

Letter 2 – White Flannel Moth Caterpillars


Subject: Caterpillar ID
Location: Northern Virginia
January 5, 2017 7:50 am
Found these in early fall in Northern Virginia. Can’t find a picture of it anywhere. Any idea what it is?
Signature: Chad

White Flannel Moth Caterpillars

Dear Chad,
You should handle these White Flannel Moth Caterpillars,
Norape ovina, with caution because according to BugGuide:  “Caterpillar has stinging spines.”


  • 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.

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