Caterpillars are the larval stage of butterflies and moths. Most caterpillars are completely harmless to humans. However, some species have defensive mechanisms like spines, spikes, and venom that can cause irritation or injury. These are known as stinging caterpillars
What Makes Caterpillars Sting?
Stinging caterpillars have specialized hollow hairs or spines that are connected to venom sacs. When these spines penetrate the skin, they break off and release toxic venom. The venom causes irritation, rashes, swelling, blisters, and can even trigger serious allergic reactions in some people.
The severity of the sting depends on the particular species of caterpillar. Larger, more mature caterpillars tend to have more potent venom. Some species like the puss caterpillar can cause excruciating pain that lasts for days.
Common Stinging Species
Some stinging caterpillars commonly encountered in North America include
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Puss caterpillar – Covered in a furry brown coat that hides toxic spines underneath. The sting is severely painful.
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Saddleback caterpillar – Recognizable by its brown and green coloration. It has prominent horns that contain irritating venom.
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Io moth caterpillar – Spiky yellow and black caterpillar. The sting causes irritation and swelling.
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Buck moth caterpillar – Large black caterpillars with red-tipped spines full of potent venom. The sting causes intense radiating pain.
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White flannel moth caterpillar – Yellow and black fuzzy caterpillar. The short spines scattered throughout its coat can cause painful stings.
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Hickory tussock moth – Black and white caterpillar with tufts of venomous spines along its back. Can cause skin rashes.
Symptoms and Treatment
Symptoms of stinging caterpillar exposure can include:
- Instant pain, burning, and itching
- Redness, hives, and swelling
- Headache, abdominal distress, nausea
- Blistering and dermatitis
If spines are stuck in the skin, remove them carefully with tape. Wash the area thoroughly with soap and water. Apply an ice pack to reduce pain and swelling. OTC antihistamines and hydrocortisone cream can help relieve itching. Seek medical attention for severe reactions.
Prevention
To avoid stinging caterpillars:
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Learn to identify species in your area. Be extra cautious around oak, willow, and fruit trees where stinging species often feed.
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Wear gloves and long sleeves when working around vegetation.
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Don’t touch fuzzy or spiky caterpillars. Use caution removing them from plants.
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Check clothing andgear for caterpillars before packing them away.
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Teach children not to touch caterpillars without supervision.
Stinging caterpillars can’t sting voluntarily like bees. With proper identification and precautions, most stings can be avoided. Being able to recognize and steer clear of venomous species is key to preventing a painful encounter.
How Should I Deal With Stinging Caterpillars?
Question:
I just found five small spiky caterpillars on a tree sapling and checked online that they are poisonous. Should I get rid of them and if so, how?
Answer:
There are some caterpillars that sting as a defensive mechanism against predators. An example is the fantastical Saddleback Caterpillar that Dr. Doug Tallamy discusses with me in this video interview.
This compelling caterpillar turns into a rather mundane looking adult moth that is harmless.
When you touch a Saddleback Caterpillar, or other stinging caterpillar species, their spines embed in your skin and break off. In the vast majority of cases, this will simply cause irritation and rash (see below for treatment). The severity of a given person’s reaction will be determined by that person’s sensitivity and by the species of caterpillar.
The Puss Caterpillar, the larval stage of the Southern Flannel Moth, is considered to deliver the most toxic sting of any native caterpillar in the U.S. Its cute, furry appearance, reminiscent of a certain politician’s remarkable hairdo, makes it irresistible to touch, resulting in a nasty surprise.
If stung by a caterpillar, remove the spines with tweezers and use Scotch tape over the area to pull out remaining spines. There is a good reference for immediate treatment on wikihow. For folks who are known to be highly allergic to other insects, like bees, or have impaired immune systems, a trip to the ER would be prudent. I would also suggest an ER visit if you are stung by a Puss Caterpillar.
Caterpillars, even the stinging kind, are important to our ecosystems and have many predators – they provide critical protein to birds and are a food source for certain wasp species (see the video).
Just like other insects that we love to hate, such as paper wasps and yellow jackets, stinging caterpillars are an important part of nature’s food webs and deserve our respect, as well as caution.
The best practice is to leave stinging caterpillars alone and avoid touching them. To protect against accidental contact, wear a pair of puncture-resistant rose gloves when pruning and gardening.
From Kim Eierman at EcoBeneficial!
Photo: Saddleback Caterpillar on Arrowwood Viburnum
Buy a copy of The Pollinator Victory Garden!
STUNG by a VENOMOUS Neon Caterpillar!
FAQ
What happens if a fuzzy caterpillar stings you?
- Immediate, Intense Pain: The pain can be described as a burning sensation, often coming in waves.
- Swelling, Itching Rash: A rash with red blotches and raised ridges is common.
- Other Symptoms:
- Restlessness and anxiety
- Nausea and vomiting
- Fever
- Muscle cramps
- Swollen glands
- In some cases, symptoms of shock
- Restlessness and anxiety
- Blisters: Blisters can form and last for weeks.
- Anaphylaxis: In rare cases, a severe allergic reaction (anaphylaxis) can occur.
What should you do if you touch a stinging caterpillar?
- Remove the toxin-laden hairs from your skin. …
- Wash the skin thoroughly with soap and water.
- Apply an ice pack to reduce swelling and pain.
- Create a paste using baking soda and water and slather it on the affected skin to reduce itching.
What do stinging caterpillars turn into?
This compelling caterpillar turns into a rather mundane looking adult moth that is harmless. When you touch a Saddleback Caterpillar, or other stinging caterpillar species, their spines embed in your skin and break off. In the vast majority of cases, this will simply cause irritation and rash (see below for treatment).
How can I tell if a caterpillar is poisonous?
As a general rule of safety, any brightly colored caterpillars with spines, bristles, or a fuzzy appearance might be venomous and should not be touched. Although you may know which caterpillars to look out for, it’s difficult to prevent stings since they often feed on the leaves underside, which makes them hard to see.