Puss Moth Caterpillar Sting: What to Know and How to Handle It

The puss moth caterpillar, also known as the asp caterpillar, is known for its deceivingly cute appearance and its potent sting. They can be found in the southern United States and are considered one of the most toxic caterpillars in North America. While their fuzzy exterior may resemble a harmless caterpillar or a cat’s fur, the venomous hairs beneath their fluff can cause severe pain and other symptoms upon contact.

When people come into contact with the puss moth caterpillar, the venomous hairs become embedded in their skin, leading to intense throbbing pain and burning. Alongside the pain, stinging victims may also experience erythematous spots, rashes, and abdominal pain. In more susceptible individuals, symptoms may escalate to include swelling, nausea, headache, and lymphadenopathy.

This deceptive creature, which thrives in shade trees, shrubbery, parks, and areas surrounding homes and schools, has a bimodal peak in late spring and late fall. As a result, the awareness of this caterpillar and its potential danger is crucial, especially during these periods, to prevent any unwarranted contact and painful consequences.

Puss Moth Caterpillar Overview

Identification and Appearance

The Puss Moth Caterpillar, also known as Megalopyge opercularis or Asp Caterpillar, is a venomous caterpillar found in the Southern United States. It is recognized by its teardrop-shaped body covered in long silky hairs, giving it a fluffy appearance. These hairs can range in color from yellow to gray.

Some key features include:

• Teardrop-shaped body
• Long, silky hair
• Yellow to gray coloration

Habitat and Distribution

Puss Moth Caterpillars, or Asps, are primarily found in the Southern United States, including states such as Virginia, Texas, and others. They typically inhabit areas with trees, shrubs, and foliage, posing a potential risk in residential areas, parks, and schools.

Life Cycle and Behavior

The life cycle of the Puss Moth Caterpillar consists of four stages:

1. Egg: Small, elongate with rounded ends, laid in rows or clusters on foliage or twigs.
2. Larva (caterpillar): Venomous and covered in long, silky hairs. Capable of delivering painful stings throughout all stages.
3. Pupa: Forms a cocoon woven with their own hairs.
4. Adult: Known as the Southern Flannel Moth, with fluffy, wavy, flannel-like scales.

A key aspect of their behavior is their ability to deliver potent stings when touched or pressed against the skin. The sting’s severity increases as the caterpillar grows in size. Therefore, caution is advised when encountering these caterpillars in their natural habitat.

Venom and Stinging Mechanism

Venomous Hairs and Sting

The puss moth caterpillar, or Megalopyge opercularis, is characterized by its fluffy appearance. However, beneath this soft exterior lie venomous spines that can inflict painful stings when touched. These caterpillars’ hairs contain a potent toxin that causes extreme discomfort and pain when it comes into contact with the skin.

Venomous hairs features:

• Fine and soft
• Concealing venomous spines
• Potent toxin causing pain

First Aid and Treatment

In the event of a puss moth caterpillar sting, it’s crucial to follow appropriate first aid and treatment measures. Some methods to alleviate pain and minimize symptoms include the following:

• Remove any visible hairs using tweezers or adhesive tape
• Apply an ice pack to reduce swelling
• Take over-the-counter pain relievers as needed
• Avoid scratching the affected area to prevent further irritation or infection

When comparing a puss moth caterpillar sting to other insect stings, it’s worth noting that the puss moth’s venomous hairs can provoke a more painful reaction. In addition, while some stinging insects may cause similar effects, the puss moth caterpillar is considered one of the most dangerous stinging caterpillars in the US, mainly due to its powerful toxin.

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 – Another Puss Moth Caterpillar from Ireland

catarpilar
Hello Daniel,
Thanks for your answer, i found another one in the garden its the same as the first one but different collour, is it the same?? and the moth on the wall is that one of the catarpilar’s it was 5 cm Kind regards
Jeannette

Hi again Jeannette,
Thanks for sending us another photo of another Puss Moth Caterpillar, Cerura vinula. Many typically green caterpillars change colors, often to brown, red, orange, pink or purple just before pupation. We suspect that is about to happen with this individual. We will address you moth query in a separate email.

Letter 2 – Ecuadorean Puss Moth, probably

Info request
Hi,
Saw your site and wondered if you can help. I saw this in Ecuador…Amazon Rainforest. From information on your site it looks to be a puss caterpillar. Is this correct and would it be in Ecuador? Thanks for any information.
Best Regards,
Alan

Hi Alan,
If this photo came from the U.S., we would say Puss Moth Caterpillar, or Asp, for sure. Chances are good it is a close relative.

Letter 3 – Our 20,000th Posting: Puss Moth Caterpillar or Oruga de Polilla Gato from Ecuador

Subject: Caterpiller with a nasty sting
Location: Mindo Ecuador
April 3, 2015 5:09 pm
Bugman, check out this beauty found while cutting some brush in Mindo, Ecuador. It left some of its fine hairs behind on the branch it was knocked off of. The local guy I hired to help me told me to watch out for these falling on your head when battling the thicket: a sting from this will put you in the house all day with a fever and intense pain. I didn’t test his claim for myself but I did manage to get these pictures.
Signature: PDB

Dear PDB,
This really is a beautiful caterpillar, and it is a wonderful choice to celebrate the 20,000th posting on our site, quite a milestone that fills our tiny staff with immense pride.  At first we thought this must be a Stinging Slug Caterpillar in the family Limacodidae because of its resemblance to a Monkey Slug from North America, but our search eventually brought up an image of a Puss Moth Caterpillar (Oruga de Polilla Gato) in the family Megalopyge on FlickR where it states:  “The’hairs’ are very urticant and touching them produces strong reactions that may include hospitalization”.  Puss Moth Caterpillars from North America are also stinging caterpillars that are commonly called Flannel Moth Caterpillars or Asps.  We then tried searching the Monkey Slug genus Phobetron and found an individual from Suriname posted on Flickr, and after careful consideration, we cannot say for certain in which family your caterpillar should be classified, but we are leaning towards the family Megalopyge.  We then found an excellent image by Andreas Kay matching your caterpillar on FlickR, but alas, it is only identified as a Stinging Flannel Moth Caterpillar in the family Megalopygidae.  The best visual match we located was taken by Shirley Sekarajasingham and posted to FlickR, but again, it is only identified to the family level.  Perhaps one of our readers would like to continue searching for a genus or species match for our 20,000th posting.

Letter 4 – Prepupal Puss Moth Caterpillar from Spain

Subject: Caterpillar ID
Location: S Andalucia
June 5, 2017 10:08 am
I took these photos this morning in Southern Spain. The Caterpillar is about 5 Cms long and what I assume to be the rear end has a flat circular area with a whitish ring and a reddish centre.
Signature: Garth Nicholson

Dear Garth,
This is either a Puss Moth Caterpillar, Cerura vinula, or a closely related species.  We found images on the British site Wildlife Insight of Puss Moth Caterpillars and the site provides this information:  “At this stage the Puss Moth prepupating caterpillar turns from green to a dark purplish colour.  Having stopped feeding it will often leave the food plant to search for a suitable place to pupate.  It is at this stage, when wandering over the ground, that it is frequently come across – resulting in many caterpillar identification requests.  Using its strong jaws the Puss Moth caterpillar forms a very hard cocoon by chewing up bark and cementing it with silk into crevices in tree trunks and woody/plant litter.”  According to Insecta Pro, the species is found in Spain as well as much of Europe. 

Thank you Daniel, checking the links you sent I think you have made a good ID. I realise what I thought was the rear end is in fact the front end.
Many thanks,
Garth Nicholson

Letter 5 – Puss Moth

Subject: Yellow Moth?
Location: Maryland, U.S.
April 4, 2015 4:09 am
I found what looks to be some type of moth a few years ago on vacation in Maryland. I was hoping you could help me identify it!
Signature: Anonymous

Dear Anonymous,
This is a Southern Flannel Moth or Puss Moth, Megalopyge opercularis, and though your image is several years old, your identification request is very timely because a Puss Moth Caterpillar or Asp from Ecuador is our 20,000th posting, and yours is our 20,001st.  Read more about the Puss Moth on BugGuide.

Letter 6 – Puss Moth

Subject: What is it
Location: North Central Alabama
June 29, 2017 11:58 am
I took this on the sidewalk In front of my gym, what is it?
Signature: Cathryn

Dear Cathryn,
This interesting moth is a Puss Moth.

Letter 7 – Puss Moth

Subject:  Unusual moth
Geographic location of the bug:  Lumberton, Texas
Date: 06/10/2019
Time: 07:58 AM EDT
Your letter to the bugman:  Good morning!
Walking outside i saw this neat little bug that looked like a circle. Upon closer look it is a moth, I believe, of some sort.
Can you identify it please?
How you want your letter signed:  DeeDee

Dear DeeDee,
This is a Puss Moth or Southern Flannel Moth.  The stinging caterpillar of a Puss Moth is commonly called an Asp.