Friend or Foe? How to Tell if a Caterpillar Is Poisonous

Just because caterpillars can be fuzzy and come in fun, vibrant colors, doesn’t mean they are all harmless. Some caterpillars have a venomous defense mechanism – spines that deliver a painful sting. Stay safe by knowing how to identify poisonous caterpillars. Get to know some common poisonous species and what to do if you accidentally come into contact with one.

What Does a Poisonous Caterpillar Look Like?

Poisonous caterpillars typically have distinct physical indicators that warn predators that they should not be messed with. These are some common traits that may help you identify a stinging caterpillar to avoid:

• Bright colors
• Bold patterns
• Unique shapes (like horns)
• Spines, hairs, or bristles

While many harmless caterpillars are fuzzy, venomous species typically have at least some hair or spines. On poisonous caterpillars, spines house glands that release venom upon contact. If a caterpillar looks particularly bristly, spiky, or has prominent tufts of hair, it's wise to just look from a distance.

Proceed with Caution Around These Stinging Caterpillar Species

Get to know a couple of well-known culprits:

Asp Caterpillar

Also known as the puss caterpillar, this furry caterpillar hides toxic spines beneath its coat. Often found in the southern US, the asp caterpillar is infamous for its extremely painful sting. An asp caterpillar sting can cause intense burning, swelling, nausea, and even chest pain in severe cases. The affected area may develop a rash, swelling, and redness.

But can a puss caterpillar kill you? In rare cases, a puss caterpillar sting can cause a severe allergic reaction called anaphylaxis, which is life-threatening and requires immediate medical attention.

Saddleback Caterpillar

This distinctively marked caterpillar is easily identified by the prominent "saddle" patch on its back, which is typically brown surrounded by green. It also has "horns" at both ends of its body. The saddleback caterpillar sting, while usually less severe than an asp caterpillar sting, can still cause significant pain, itching, and a red welt.

Io Moth Caterpillar

These caterpillars are recognized by their bright green bodies with a distinctive red and white stripe along each side. They're covered in venomous, branched spines. A sting from this poisonous green caterpillar can cause immediate localized pain, itching, and redness, sometimes followed by welts. In some cases, more severe reactions like headaches, fever, or nausea can occur.

Buck Moth Caterpillar

A buck moth caterpillar has a black and reddish head and small white spots all over its body. It is covered in hollow, venomous spines. Contact with these spines causes a burning, itching sensation like a bee sting.

What to Do If You Get Stung by a Caterpillar

If a poisonous caterpillar stings you, follow these steps to relieve symptoms:

1. Remove Spines: If any spines are embedded in your skin, lightly dab the area with the sticky side of tape to lift the spines. Alternatively, pull them out carefully with tweezers. Don’t rub the area, as this can push the spines deeper.
2. Clean the Area: Wash the affected skin with soap and water.
3. Apply a Cold Compress: A cold compress or ice pack can reduce pain and swelling.
4. Medicate: Over-the-counter pain relievers (like ibuprofen or acetaminophen) and antihistamines can help manage pain and itching. Hydrocortisone cream can also reduce itching and inflammation.
5. Seek Medical Attention if Necessary: If the pain is severe, symptoms worsen, or you have an allergic reaction, get professional caterpillar sting treatment.

It’s important to treat a caterpillar sting as promptly as possible.

Read more: Bug Bite Allergies

Stay Safe and Smart – Prevent Caterpillar Stings

To prevent an accidental sting, wear gloves when gardening or working outdoors. Be sure everyone in your family knows that brightly colored or unfamiliar fuzzy caterpillars shouldn’t be touched. If you're unsure whether a caterpillar is safe, remain cautious and leave it alone.

In addition to sting prevention, focus on caterpillar prevention! If caterpillars are taking over your yard, the team at Mosquito Squad Plus^® can help you identify them and deter them from your space. Our local pros offer barrier treatment services to strategically target harmful pests. Treatments help kill pests on contact and continue to deter them for up to 21 days.

Learn more about our services for controlling stinging pests when you call (877) 332-2239 or request a cost-free quote online.