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.

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.

Habitat

Saddleback caterpillars can be found in:

• Region: Eastern United States
• Timing: late summer

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.

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 Stage	Features	Duration
Eggs	Clusters on host plants	Several days
Larvae	Bright coloration, saddle-like pattern, prolegs	Several instar phases
Adult Moth	Dark 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.

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:

• Intense burning
• Inflammation
• Red blanching

More severe cases may result in:

• Rashes
• Swelling welts
• Tissue damage

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

Characteristics	Saddleback Caterpillar Sting	Bee Sting	Mosquito Bite
Type of Venom	Poisonous spines	Venom	Saliva
Immediate Symptoms	Burning, inflammation	Pain	Itching
Risk of Severe Reaction	Low to moderate	Moderate	Low
Incidence of Anaphylaxis	Rare	Rare	Extremely rare

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.

Measures	Pros	Cons
Protective Clothing	Minimizes risk of contact	Can be uncomfortable in hot weather
Using a Stick	Avoids direct contact with caterpillars	Less effective for a larger infestation
Handpicking	Eco-friendly	Requires caution and leather gloves

Other Stinging Caterpillars

North American Species

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

• Buck moth caterpillar
• Monkey slug caterpillar
• Io moth caterpillar
• White flannel moth caterpillar
• Stinging rose caterpillar

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

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.

Caterpillar	Appearance	Severity of Sting
Saddleback	Green saddle-like pattern	Milder
Buck moth	Black with red spots	Moderate to severe
Monkey slug	Brown, simulates a dried leaf	Moderate
Io moth	Green with white and red stripes	Moderate
White flannel moth	White with tufts of hairs	Mild to moderate
Stinging rose	Red and yellow stripes	Mild 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.

Conclusion

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 Caterpillar	Megalopygidae Family
Less dangerous	More dangerous
Brownish-purple saddle	No distinct saddle
Feed on various trees	May 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.

Footnotes

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, whatsthatbug.com 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

BUG ID
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!
Deborah

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

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