Are Saddleback Caterpillars Dangerous? Uncovering the Truth

Saddleback caterpillars are distinctive for their bright green color and the brownish-purple spot resembling a saddle on their backs.

These small creatures might fascinate you with their unique appearance, but they can pose a danger due to the venomous spines on their bodies.

When these spines come into contact with skin, they can deliver a painful sting, causing various symptoms such as a burning sensation, rash, and swelling.

Are Saddleback Caterpillars Dangerous

Some people might experience more severe reactions, such as nausea, muscle cramps, or difficulty breathing.

It’s essential to be aware of these potential dangers, especially when you’re out in nature, as saddleback caterpillars can be found on various trees and shrubs, including oak, cherry, and plum.

Identifying Saddleback Caterpillars

Physical Characteristics

The saddleback caterpillar is known for its distinct appearance:

  • Length: about 3/4 inch when mature
  • Color: dark brown at both ends and bright green in the middle
  • Pattern: purplish-brown oval patch (saddle) in the green area

These caterpillars possess urticating hairs on their body, which can cause painful stings.

They also exhibit aposematic coloration, meaning bright warning colors that signal toxicity or distastefulness.


Saddleback caterpillars can be found in:

These caterpillars spin silk cocoons to overwinter, providing tough protection.

Host Plants

Saddleback caterpillars feed on various trees and shrubs:

  • Basswood
  • Chestnut
  • Cherry
  • Plum
  • Oak

Identifying the host plant can aid in confirming the presence of saddleback caterpillars.

They are generally found feeding on the leaves, occasionally posing risks to certain plants due to defoliation.

Saddleback Caterpillar

Life Cycle and Behavior

Eggs and Larvae

Acharia stimulea, also known as the saddleback caterpillar, goes through several life stages.

During the egg stage, these caterpillars lay small clusters of eggs on their host plants, such as corn.

Upon hatching, the larvae emerge and begin to feed on the leaves. The larva stage consists of multiple instar phases, wherein each stage lasts only a few days.

  • Egg stage: Small egg clusters laid on host plants
  • Larva stage: Multiple instar phases in which larvae feed on plant leaves

During their growth, saddleback caterpillars develop prolegs to crawl and move around their environment.

These caterpillars are known for their bright coloration and unique saddle-like pattern.

Moth Stage

Upon reaching maturity, saddleback caterpillars enter their pupa phase, where they transform into moths.

The adult moth is dark brown and fuzzy in appearance.

As native species, these moths play an essential role in the ecosystem by helping pollinate plants.

Life StageFeaturesDuration
EggsClusters on host plantsSeveral days
LarvaeBright coloration, saddle-like pattern, prolegsSeveral instar phases
Adult MothDark brown, fuzzy appearance, pollination role

Remember, while the saddleback caterpillar may look fascinating, it’s crucial to avoid touching them due to their urticating hairs that can cause painful stings.

By understanding their life cycle and behavior, we can better appreciate this unique and fascinating creature.

Saddleback Caterpillar

Are Saddleback Caterpillars Dangerous?: Potential Effects of Stings

Mechanism of Stinging

Saddleback caterpillars possess urticating hairs on their body, which can cause painful stings when touched.

These hairs deliver venom upon contact with human skin, resulting in an adverse reaction.

Severity of Symptoms

Reactions to saddleback caterpillar stings can greatly vary in severity. Common symptoms include:

More severe cases may result in:

Anaphylactic Shock and Allergic Reactions

While rare, some individuals may experience severe allergic reactions to these stings, leading to anaphylactic shock.

This is a life-threatening condition, and immediate medical attention is necessary. Signs of anaphylactic shock include:

  • Difficulty breathing
  • Rapid or weak pulse
  • Fainting

In case of a sting:

  • Remove any spines from the skin carefully
  • Wash the affected area with soap and water
  • Apply icepack to reduce swelling
  • Seek medical help if symptoms worsen or persist

Comparison of Saddleback Caterpillar Stings and Other Insect Bites

CharacteristicsSaddleback Caterpillar StingBee StingMosquito Bite
Type of VenomPoisonous spinesVenomSaliva
Immediate SymptomsBurning, inflammationPainItching
Risk of Severe ReactionLow to moderateModerateLow
Incidence of AnaphylaxisRareRareExtremely rare

Saddleback Caterpillars

Treatment and Prevention

First Aid Measures

  • Clean the area: Gently wash the affected skin with soap and water to remove any remaining venom or irritants.
  • Relieve pain and itching: Apply an ice pack to the area to reduce swelling and relieve pain.
  • Remove urticating hairs: Use adhesive tape to remove any remaining caterpillar hairs from the skin1.

Avoiding Contact

  • Wear protective clothing like a long sleeve shirt, pants, and gloves when working outdoors or in the garden.
  • Be cautious when approaching unfamiliar vegetation, especially if you notice signs of caterpillar infestations.

Garden Safety Measures

  • Use a stick to gently move any branches or foliage with suspected caterpillar activity.
  • Handpick caterpillars with caution, using leather gloves to avoid direct contact with their urticating hairs2.
  • Monitor the garden regularly for infestations and take appropriate actions to control caterpillar populations.
Protective ClothingMinimizes risk of contactCan be uncomfortable in hot weather
Using a StickAvoids direct contact with caterpillarsLess effective for a larger infestation
HandpickingEco-friendlyRequires caution and leather gloves

Other Stinging Caterpillars

North American Species

There are several species of stinging caterpillars in North America, such as:

These caterpillars differ in their appearance and the severity of their stings. They can be encountered on various trees and shrubs.

Saddleback Caterpillar

Comparison to Saddleback Caterpillars

Saddleback caterpillars are characterized by their unique appearance having a green saddle-shaped pattern on their backs.

Their stings are generally milder than those of other stinging caterpillars.

CaterpillarAppearanceSeverity of Sting
SaddlebackGreen saddle-like patternMilder
Buck mothBlack with red spotsModerate to severe
Monkey slugBrown, simulates a dried leafModerate
Io mothGreen with white and red stripesModerate
White flannel mothWhite with tufts of hairsMild to moderate
Stinging roseRed and yellow stripesMild to moderate

As seen in the table, each caterpillar varies in terms of physical appearance and sting severity.

It is important to exercise caution when dealing with any of these caterpillars.


Saddleback caterpillars can be dangerous due to the stinging hairs found on their body.

Accidental contact with them may cause skin irritation and allergic reactions.

The caterpillar is about 1 inch long and has a distinct brownish-purple spot on its back that resembles a saddle.

It feeds on various trees and shrubs, including basswood, chestnut, cherry, plum, and oak.

Saddleback caterpillars are considered less dangerous than some other venomous caterpillars, such as those from the moth family Megalopygidae.

However, caution is still necessary when encountering them.

To provide a more comprehensive understanding, here’s a comparison table:

Saddleback CaterpillarMegalopygidae Family
Less dangerousMore dangerous
Brownish-purple saddleNo distinct saddle
Feed on various treesMay have specific host plants

It’s essential to be aware of the possible hazards these creatures pose and take necessary precautions when spending time outdoors.

In summary, be cautious around saddleback caterpillars.


  1. Caterpillar Venom: A Health Hazard of the 21st Century – PMC

  2. Stinging Caterpillars on Shrubs – University of Maryland Extension

Reader Emails

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

Letter 1 – Saddleback Caterpillar

Found this bug in our vegetable garden. The pain from the sting from this critter didn’t last very long. I sent the photo to a good friend of mine in Canada and he emailed your web site to me.

Checked out your site and didn’t see it listed. It’s very beautiful I think and I though you may be interested. We live in central Virginia. I looks somewhat like the Saddleback’s I’ve seen on your web site. Do you know what it is?
Bert and Cheryl

Hi Bert and Cheryl,
This is a Saddleback Caterpillar and they do sting.

Letter 2 – Saddleback Caterpillar

Yes this one stings. Is it a saddleback? doesn’t look like the on on your site. Fairfax VA
Sherley Channing

Hi Sherley,
We believe we have about 10 images of Saddleback Caterpillars on our site and they look nearly identical to this specimen.

Letter 3 – Saddleback Caterpillar

unknown caterpillar
Please help me. I came across this little caterpillar in Cuernavaca, Mexico this past September. it was on the hood of a car, as you can see in the photo. Can you please tell me what kind of bud it is? Thank you!

Hi Deborah,
This is a Saddleback Caterpiller. It is a stinging species that is found in much of the U.S. as well.

Letter 4 – Saddleback Caterpillar

Scary Caterpillar
August 30, 2009
My daughters and I found this while doing yardwork. My daughter accidentally bumped it while we were taking pictures of it and she said it stung real bad.

I did remove what looked like a tiny hairlike stinger! I would love to know what this bug is!
Thanks for your help!!! Debbie
Henderson Kentucky

Saddleback Caterpillar
Saddleback Caterpillar

Hi Debbie,
The Saddleback Caterpillar, Acharia stimulea, in the family Limacodidae is one of the Stinging Slug Caterpillars.


  • Bugman

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

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  • 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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2 thoughts on “Are Saddleback Caterpillars Dangerous? Uncovering the Truth”

  1. I saw a saddleback caterpillar a while back and I got stung by it. It left big welts on my arm, and I didnt know how to treat the stinging, so I put ice on it. Do you know any better way to treat a sting from the saddleback caterpillar ? Thanks!

  2. Oh, I had two of these together in my yard in GA today. I took photos, but it looked prickly so I didn’t attempt to touch it (glad of that after having read comments about stings)


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