The io moth caterpillar is a fascinating yet potentially harmful insect due to its painful sting. While eye-catching in appearance, these caterpillars possess hollow spines that can break off, embedding themselves deeply into the skin upon contact. The sting often leads to burning or itching sensation, along with redness around the affected area source.
As a defense mechanism, the sting of an io moth caterpillar may serve as a deterrent against predators. However, for humans exposed to these insects, it’s crucial to be cautious and avoid direct contact. If you come across io moth caterpillars, it’s best to admire their beauty from a safe distance to avoid any unnecessary pain or discomfort.
Io Moth Caterpillar Basics
The Io moth caterpillar (scientific name Automeris io) is a visually striking member of the Lepidoptera order and the Saturniidae family. This caterpillar is pale green with white and yellow stripes running along the length of their bodies. They have yellow or green fleshy protrusions tipped in black, which are responsible for their painful sting.
Habitat and Range
Io moth caterpillars are found in various habitats, particularly in forests and park-like areas. They are widespread throughout the eastern United States, ranging from Florida up to Maine and as far west as Texas.
The life cycle of an Io moth caterpillar goes through four phases: egg, larva (caterpillar), pupa, and adult moth. Adult moths lay their eggs on a variety of host plants, where the caterpillars feed on the leaves before eventually developing into pupae. Once they’ve metamorphosed into adult moths, they focus on using their short lifespan to reproduce and continue the cycle.
- Egg: Laid by adult Io moths on host plants.
- Larva (caterpillar): Feeds on leaves of host plants.
- Pupa: Metamorphoses inside cocoon.
- Adult moth: Main focus is reproduction.
Stinging Mechanism and Effects
Io moth caterpillars have rows of stinging spines on their body, which contain a painful venom. These spines, also known as stinging hairs, are attached to poison glands and release toxins when something, like human skin, comes into contact with them.
Signs and Symptoms
Some common symptoms experienced after being stung by an Io moth caterpillar include:
- Painful, burning sensation
In some cases, the symptoms can be more severe, such as when the toxin comes into contact with the eyes or if the person has an allergic reaction.
If stung by an Io moth caterpillar, the following steps can help alleviate symptoms:
- Gently remove the stinging hairs using a piece of tape
- Wash the area with soap and water
- Apply a cold compress to reduce swelling
- Consider taking an over-the-counter pain reliever or antihistamine for pain and itching
To avoid caterpillar stings, consider these preventative measures:
- Be cautious when handling unfamiliar caterpillars
- Wear protective clothing when in areas with known stinging caterpillars
- Educate yourself on the appearance of venomous caterpillars, such as the Io moth, in your region
Io Caterpillar’s Interactions with Plants
Common Host Plants
The Io moth caterpillar (Automeris io) is found on various plants in the Eastern United States. Some of its common host plants include:
- Crape myrtle
Damage to Trees and Shrubs
Io moth caterpillars can cause significant damage to trees and shrubs through defoliation. They consume the leaves of their host plants, resulting in the following negative effects:
- Reduced plant growth
- Weak and unhealthy trees
- Lower yields in agricultural crops
A comparison of the damage caused by Io caterpillars to various tree species is shown in the table below:
|Partially consumed leaves
|Minimal leaf damage
|Loss of foliage
Despite their destructive nature, it is important to remember that the Io moth caterpillar is just one part of a complex ecosystem and plays a role in the food chain, providing a food source for various predators.
Comparison with Similar Caterpillars
Buck Moth Caterpillar
The Buck Moth Caterpillar is commonly found throughout southeastern United States, including Florida. It is easily recognized by its black and white coloration, which is different from the Io moth caterpillar’s pale green hue with white and red stripes. While both caterpillars possess stinging spines, the Buck moth caterpillar tends to cause more intense pain, similar to a bee sting.
The Puss Caterpillar, also known as the Flannel Moth Caterpillar, is primarily found in Texas and southeastern states. It is one of the most venomous caterpillars in the United States. Unlike the Io moth caterpillar’s distinctive striping, the Puss caterpillar boasts a unique, furry appearance with a tail-like protrusion, resembling a kitten. Both caterpillars have stinging spines, but the Puss caterpillar’s sting can cause severe pain and malaise, potentially lasting for hours.
The Saddleback Caterpillar is another member of the stinging Limacodidae family, like the Io Moth Caterpillar. This caterpillar’s primary identifying feature is a prominent, saddle-shaped marking on its back, setting it apart from the Io moth caterpillar’s long stripes. Both caterpillars are often found on dogwood trees, and both possess stinging spines. However, the Saddleback caterpillar’s sting can cause severe irritation, pain, and potential allergic reactions.
Other Slug Caterpillars
Slug caterpillars such as the Spiny Oak Slug also belong to the Limacodidae family. These caterpillars display a range of colors and patterns, including the Io moth caterpillar’s stripes, and they all share one common feature: stinging spines called setae. While the severity of the stings can vary, it’s important to avoid handling or disturbing these caterpillars.
|Pale green, white & red stripes
|Eastern United States
|Black & white
|Southeastern United States
|Furry, resembling a kitten
|Texas and Southeast
|Green with saddle-shaped marking
|Eastern United States
|Spiny Oak Slug
|Varied colors, with setae
|Eastern United States
- Features of different stinging caterpillars:
- Possess stinging spines called setae
- Varied coloration and patterns for camouflage
- Found in various regions across the United States
- Often inhabit trees like dogwood, oak, and elm
Interesting Io Moth Caterpillar Facts
The Io moth caterpillar is a fascinating creature found in North America.
- Males and females: Male Io moth caterpillars have feathery antennae and are larger than female caterpillars. Females have slightly smaller and less fuzzy antennae.
Io moth caterpillars have a unique defense mechanism against predators.
- Eyespots: They have large, colorful “eyes” on their wings. These eyespots resemble the eyes of predators, deterring potential threats.
These caterpillars can also spray an irritating fluid when disturbed.
- Sting: Their spines release powerful venom that can cause pain and swelling upon contact.
Some animals still attempt to prey on Io moth caterpillars.
- Wasps: Some wasp species hunt Io moth caterpillars to lay their eggs on them. The wasp larva feeds on the caterpillar while it’s still alive.
The Io moth caterpillar’s numbers can vary across their range.
- Distance: Caterpillar populations may fluctuate greatly depending on the region in North America.
These caterpillars can even affect humans in certain situations.
- Sport: If you accidentally touch an Io moth caterpillar during an outdoor activity like hiking, you may experience pain and discomfort.
Here’s a comparison table between Io moth caterpillars and another well-known caterpillar, the monarch butterfly caterpillar.
|Io Moth Caterpillar
|Monarch Butterfly Caterpillar
|North and South America
|Eats milkweed; toxic to predators
|Green with spines and eyespots
|Brightly striped black, white, and yellow
In conclusion, the Io moth caterpillar is a unique and interesting species with its intriguing appearances and defense mechanisms.
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 – Io Moth Caterpillars
Subject: 8-10 LARGE caterpillars on Crepe Myrtle tree in Central Florida
Location: Central Florida, USA
September 14, 2013 1:31 pm
Hello! Love your website (and bugs!!). Help please???
I have 8-10 fairly large caterpillars, about 4-6 inches long, BRIGHT yellow green with a dark red & white band on both sides & numerous spiny tufts on the dorsal & both sides. They are an impressive group, and currently feasting on the leaves & branches of an immature Crepe Myrtle tree. This is the 3rd day I have seen them.
I am in NE Orlando, in Central Florida. My house is adjacent to 2 lakes & a 10 acre wooded semi-marshy conservation area. I am new to this house, and have NEVER seen these before, although I have lived in Central Florida for 25+ years. These gorgeous guys have stripped most of the new & younger leaves from my Crepe Myrtle. Haven’t touched the flowers or the seeds or woody parts so far. They appear to have a stinging aspect, so I haven’t touched yet.
What are they, please?? Keying them out has proved difficult for me, and I appreciate your help and expertise. Are they moth or butterfly? Can I raise them??
Thank you VERY MUCH for any help!
Signature: Pat O
You have a healthy brood of Io Moth Caterpillars, Automeris io, and they will metamorphose into lovely Giant Silkmoths with pronounced eyespots on the underwings. Adult Io Moths exhibit sexual dimorphism. The larger female Io Moths have brown upper wings while the male Io Moths have bright yellow upper wings. You are correct that the caterpillars are capable of stinging. We believe your estimate of 4-6 inches in length is a bit exaggerated, and we would put the mature caterpillars maximum length closer to 3 1/2 inches. We are especially amused by the ruler in your photo which has the number side away from the camera. You can raise Io Moth Caterpillars to maturity with little effort. We would urge you to keep both the caterpillars and pupae outdoors, or at least in an area where they are the same temperature as the outdoors. You do not want them to emerge early in a heated environment. Adult Io Moths do not eat and they only live a few days, long enough to mate and reproduce.
Subject: 8-10 big green caterpillars in C Florida IDENTIFIED, i think!
September 14, 2013 2:48 pm
Just an update to my prior question concerning the large bright green caterpillars I found on my Crape Myrtle tree.
I think I have identified them! Using tips from other readers of your site, I backtracked the pests of Crape Myrtle using HOSTS database of the Natural History Museum website (limited success, but a good start). ButterfliesAndMoths.org was a good source also. Then went to Discover Life website ID guide. Found them!! I think my hungry young guests are Automeris io larvae/caterpillars!! And yes, they DO sting……
I appreciate your website, and the opportunity & links to continue to learn.
Ed. Note: We didn’t realize that Pat had identified her Io Moth Caterpillars when we created the posting.
Letter 2 – Io Moth Caterpillar
What kind is it?
Just wanted to know what kind of caterpillar this is. I live in Harford Co., Maryland. My husband found it on a green Japanese maple tree. It had already eaten a few limbs. Not sure if its a moth or butterfly. Thanks,
The spines of the Io Moth, Automeris io, caterpillar are mildly poisonous. It is easily recognized because of the red and white stripes. The adult moths have eyespots on their underwings. They are small Silkworm moths, the male with yellow upper wings and female with brownish upper wings. They are sometimes found on corn and other garden crops.
Letter 3 – Io Moth
fat orange bug
February 4, 2010
fat thick body orange bug with eye shaped patterns on its wings. didn’t move around much and was able to expand it’s wings open using a piece of grass
This is a female Io Moth. She can be distinguished from the male of the species because the male has yellow upper wings.
Letter 4 – Io Moth
Sphinx moth? Which species?
I just found your site via google and am delighted with the questions, answers, and photos! We live in southern West Virginia, near the New River Gorge, surrounded by many acres of tall second-growth poplar, oak, maple, beech, and hemlock. I found a lovely golden moth with a plump, fuzzy gold body on my office screen this morning. I think it’s a Sphinx moth, but my most complete reference book (Golden Guide to Butterflies and Moths!) doesn’t have an image that matches it. Then, this afternoon my husband found four moth wings in the garage, under the 66 Mustang he’s restoring, and I thought they looked like the wings on “my” moth, so I took some photos. Here are two: one of “my” moth and “his” wings; the other of the moth (now “ours”) alone. What, please, is the name of our moth?
Ellen Scheel and Julian Skaggs
Hi Ellen and Julian,
Your moth is not a Sphinx, but a Giant Silkworm or Saturnid Moth. It is a male Io Moth, Automeris io. These are beautiful moths. The female has brown upper wings. The caterpillar has stinging spines. Your moth probably did not really meet an untimely end since they live only to mate and do not eat as adults.
Letter 5 – Io Moth
Moth in Houston, TX
Attached are two pictures of a moth we found in our backyard in Katy, TX (west of Houston). Can you tell me what kind of moth it is and a little bit about it? Thanks!
We would be happy to tell you a bit about your female Io Moth, Automeris io. The male can be recognized by his yellow upper wings while the female’s are brown. This is a Saturnid or Giant Silk Moth. They do not feed as adults, but have ravenous caterpillars. We have just received several caterpillar photos and posted one.
Letter 6 – Io Moth
I took this picture mid-July but cannot find out what kind of moth this is. Any information on this beautiful furry little creature would be appreciated. Your website helped me identify another moth that I took pictures of in the same flower garden. The Hummingbird Clearwing Moth. I live in central Illinois and have seen more variety of moths this year than any other. Thanks,
P.S. Great website!
This is a male Io Moth, Automeris io.
Letter 7 – Io Moth
Texas Moth with a Hammerhead?
May 25, 2010
This moth and another were resting on some discarded vegetation in my mother’s back yard which is located in a very wooded part of Southeast Texas. It was spotted on May 24 on a hot muggy day. I’ve included an image of a second moth too.
Porter Texas.. northern suburb of Houston
Your lovely moth is a male Io Moth, Automeris io. Male Io Moths are yellow while females are a reddish brown. Both males and females have distinctive eyespots. According to BugGuide, the Io Moth is also called the Peacock Moth.
Letter 8 – Io Moth Caterpillar
Any idea what kind of caterpillar this is?
An hour ago I was out in the yard & came across this caterpillar..I’ve not seen it move much so I’m thinking it will be soon going into chrysalis or making a cacoon,whichever it does.The caterpillar was found on my Hyacinth bean vine . Unlike most women my age that I know I LOVE bugs.I go out looking for them..
Thanks for the compliment. Your caterpillar is an Io Moth, Automeris io. We have some adult moth images on our Saturnid or Silkmoth page. The caterpillar is very fond of cherry leaves. Careful handling that caterpillar. The spines can cause a stinging sensation if they penetrate the skin.
Letter 9 – Io Moth Caterpillar
I am delighted by the wonderful pictures. My neighbor here in the campground found the attached caterpillar in a box of garlic sent from B.C. Canada. She does not know if it crawled into the box after it was opened in her tent or it it is a stowaway from Canada. It stung her and though concerned did not want to destroy it. Can you help us identify it?
Luckily, the sting of the Io Moth Caterpillar only results in mild discomfort.
Letter 10 – Io Moth Caterpillar
What is it?
I found this caterpillar happily munching on one of my hibiscus plants. I checked your web page but was unable to identify it based on all the other photos. Can you tell me what it might be?
Punta Gorda, Florida
This is an Io Moth Caterpillar, one of the Giant Silkworm Moths, though not one of the largest. The spines are mildly poisonous.
Letter 11 – Io Moth Caterpillar
My daughter brought this creature home from school and loves it! She wants to know what it will turn into. She also wants to be sure she is feeding him the right food. Maybe you can help? We live in West Palm Beach, FL if that helps!
This is an Io Moth Caterpillar, Automeris io. It will eat a wide variety of leaves, including wild cherry, hackberry, willow, mesquite, redbud, currant, blackberry, and pear. The spines, if they penetrate the skin, will cause a painful irritation. The adult moths have eyespots on the lower wings and exhibit sexual dimorphism. The males are yellow and the females have brown upper wings. They are beautiful moths.
Letter 12 – Io Moth Caterpillar
We were making fodder shocks with the corn stalks and our son yells, “OUCH!” His father calls him a wimp and tells him to stop belling aching. Moments later, Pops yells, OUCH what the *?@!*# something just stung me!! A closer look revealled, the Io Moth Catipillar (We identified by your website). Stephen tells the kids to back away, Don’t Touch it! I was working in the garden with the guys and had to check out this vicious catipillar that was dropping the guys like flies. I have to admit what a wild little creature and grabbed the camera. I would have taken some pictures of the bite marks and attached- had the camera battery not died right after this shot. Enjoy,
Stephen, Jen, Jared, and Zach.
What a delightful story of a family bonding chore being interrupted by a little stinging Io Moth Caterpillar.
Letter 13 – Io Moth Caterpillar
I found this little caterpillar on the sidewalk and picked it up so that it wouldn’t get squashed. Now its at my house but it’s not eating the plants I provided for her. What type of caterpillar is it and what does it eat? Thank you for your time,
This is an Io Moth Caterpillar. Be careful, since those spines can sting. Io Moth Caterpillars feed on a variety of deciduous trees including wild cherry. The Featured Creatures website indicates: “The io moth has a long list of host plants, with over 100 recorded plant genera in North America, including such diverse plants as roses, cotton, hibiscus, azaleas, willows, clover, and palms. In Florida, io moth larvae are commonly found on oaks and other hardwoods. “
Letter 14 – Io Moth Caterpillar
Io Moth Caterpillar
My son found this caterpillar on a bush when playing outside. I homeschool my boys and we love to find caterpillars, identify them and then watch them change into their final stage. Thankfully, my boys did NOT touch this spiky little guy because I believe it is a Io Moth Caterpillar and have read that touching them can be painful. Any other info you might have about this fascinating creature would be very appreciated. The moth is beautiful and I really hope we’ll get to see it!
South Eastern PA
Your identification of an Io Moth Caterpillar is correct. Congratulations on being our first posting using our new submission form. The transition to our new and improved website has been less than smooth, but we are fully confident our new site will provide our readership with many new features.
Letter 15 – Io Moth Caterpillar
Found in bamboo tree
June 11, 2009
We live in New Orleans and found this caterpillar in a bamboo tree in our backyard. My son put it in a jar and fed it bamboo leaves (we tried other leaves but bamboo was all it ate). After about a week, it wrapped itself in leaves —- like a sleeping bag. That was about 1-1/2 weeks ago. We don’t think it’s dead but we’re not sure how long before it emerges. Is it a moth or a butterfly?
New Orleans, LA
This is an Io Moth Caterpillar. The adult moth is a beautiful creature with large eyespots on the lower wings. We have never heard of Io Moth Caterpillars feeding on bamboo. The spines on the Io Moth Caterpillar can sting if the caterpillar is not handled carefully.
Letter 16 – Io Moth Caterpillar
June 14, 2010
I found this lying under some ivy…check all the sources I usually do on-line without any success. Hope you can help me!
Beware the stinging spines of the Io Moth Caterpillar, as an encounter can be quite painful. We are postdating your letter to go live on our website next week since we are going to be away from the office for a week and we want to have daily postings while we are away.
Letter 17 – Io Moth Caterpillar
February 21, 2011 3:19 pm
Found this 2” caterpillar on the holly bush. Gorgeous green color!
This is an Io Moth Caterpillar. Handle it carefully as the spines are capable of stinging. In our submission form, the location field should be used to indicate the state or country where the sighting occurred.
Thank you for the identification and warning about the io moth. What a beautiful, emerald green! I am in Palm Bay, FL
Letter 18 – Io Moth Caterpillar
Subject: Green Caterpillar on my azalea
August 24, 2014 7:37 am
I find this bright green caterpillar on my azalea this morning – 8/24/2014 in Maryland. It looks like it has tiny pine trees growing on it (almost).
This is the caterpillar of an Io Moth, and azalea is only one of numerous possible host plants for the caterpillar. According to Featured Creatures: “The io moth has a long list of host plants, with over 100 recorded plant genera in North America, including such diverse plants as azaleas, blackberry, clover, cotton, current, hackberry, hibiscus, mesquite, palms, rear, redbud, roses and willows. In Florida, io moth larvae are commonly found on oaks and other hardwoods.” You should handle the Io Caterpillars with extreme caution as the spines can deliver a painful sting.
Letter 19 – Io Moth Caterpillar
Location: Key West
January 6, 2017 11:17 am
Florida Keys, about 2″ long. I put him on my tree. Thanks!
Your caterpillar is that of an Io Moth. Your dorsal view hides the dramatic red and white stripes on the side of the Io Moth Caterpillar. Handle the Io Moth Caterpillar with caution as they have stinging spines. The adult Io Moth is a beautiful Silkmoth with stunning eyespots.
Oooo, thank you. I let him crawl on a credit card and then put him on the tree.
Letter 20 – Io Moth Caterpillar
Subject: Green Caterpillar
Geographic location of the bug: Oklahoma
Time: 10:58 AM EDT
Hi! What is this gorgeous caterpillar going to be?
How you want your letter signed: Cindy
This is an Io Moth Caterpillar and adult Io Moths are sexually dimorphic. If this is a female, the adult female Io Moth has brown upper wings and spectacular eyespots on the underwings, while the adult male Io Moth has yellow upper wings and equally impressive eyespots. Handle with caution. Io Moth Caterpillars can sting. Because of the time of year and your location, when this Io Caterpillar spins its cocoon, it will overwinter and emerge in the spring.
Letter 21 – Io Moth Caterpillar
Subject: Green caterpillar
Geographic location of the bug: Colbert Oklahoma
Time: 10:44 AM EDT
What is this?
How you want your letter signed: Roxanne
This is an Io Moth Caterpillar. Handle with caution as they can sting.
Letter 22 – Io Moth Caterpillar
Geographic location of the bug: Upstate New York
Time: 09:34 AM EDT
Your letter to the bugman: I’m having trouble identifying this caterpillar…
How you want your letter signed: Katy
This distinctive caterpillar is an Io Moth Caterpillar, and it should be handled with caution as it has stinging spines. The adult Io moth is sexually dimorphic, with male Io Moths having yellow upper wings while those of the female Io Moth are brown. Both sexes have pronounced eye-spots on the underwings that might help to startle predators.
Letter 23 – Io Moth Caterpillar stings boy in Canada
Geographic location of the bug: Gloucester pool on the Trent Severn waterway
Time: 01:51 PM EDT
Your letter to the bugman: A caterpillar like this stung my son last weekend. After it crawled across his hand he had a double track of very itchy sore spots
How you want your letter signed: Pam
We needed to research your location which we mistakenly thought was in the UK. Now that we know you are in Ontario, Canada, your son being stung by an Io Moth Caterpillar makes sense. This is a North American species with a well documented history of stinging. According to Poison Help: “The nettling organs are borne on fleshy tubercles, and the spines are usually yellow with black tips. The spines are connected to poison glands.” You may also read about them on Entomology University of Kentucky. To the best of our knowledge, the reaction is localized and though painful, the sting is not a cause of concern, though we would always recommend seeking medical advice if there are any concerns.
Letter 24 – Io Moth Caterpillars
Spiny caterpillar on azalea bush
I found these caterpillars on my azalea bush this morning. There were probably 15 of them. I have never seen them before. As I was putting them in a container, one fell on my hand and I had a burning sensation on the area. Are these poisonous? I live in St. Petersburg FL. Thanks for your help.
There may be slight pain and irritation from contact with the spines of the Io Moth Caterpillar, Automeris io. The adult moth is a lovely “eyed” Saturniid.
Letter 25 – Io Moth Caterpillars
I found the identification for these on the WTB web site, I thought you might find it interesting to see 6 larvae dining on the underside of the same hardy hibiscus leaf. I live in a suburb (North Richland Hills) that is northeast adjacent to Fort Worth, Texas
These look like earlier instar Io Moth Caterpillars that still have some growing and several molts to go. Thanks for sending us this social grouping image.
Letter 26 – Io Moth Caterpillars
Io Moth Caterpillar (Automeris Io)?
Location: Jacksonville FL
September 1, 2010 7:10 pm
Found several of these feasting heartily on one of our Crape Myrtle trees. They are pretty large. We live in Jacksonville FL. I wanted to share this photo with you all and also verify if my research is correct 🙂
Your research is correct and these are Io Moth Caterpillars. We trust you exercised caution in handling them because the spines can sting.